Analysis of Existing Data on Lake Union/Ship Canal

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Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

October 2017

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Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Prepared for: King County Department of Natural Resources and Parks Wastewater Treatment Division

Submitted by: Timothy Clark, Wendy Eash-Loucks, and Dean Wilson King County Water and Land Resources Division Department of Natural Resources and Parks

Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Acknowledgements The authors would like to thank for following people for their contributions to this report:  Staff at the King County Environmental Laboratory for field and analytical support.  Dawn Duddleson (King County) for her help in completing the literature review.  The King County Water Quality and Quantity Group for their insights, especially Sally Abella for her thorough and thoughtful review.  Lauran Warner, Frederick Goetz, and Kent Easthouse of the U.S. Army Corps of Engineers.  Judy Pickar (project manager), Dean Wilson (science lead), and King County project team members (Bob Bernhard, Mark Buscher, Timothy Clark, Betsy Cooper, Wendy Eash‐Loucks, Elizabeth Gaskill, Martin Grassley, Erica Jacobs, Susan Kaufman‐Una, Lester, Deborah, Kate Macneale, Chris Magan, Bruce Nairn, Sarah Ogier, Erika Peterson, John Phillips, Cathie Scott, Jim Simmonds, Jeff Stern, Dave White, Mary Wohleb, and Olivia Wright).  The project’s Science and Technical Review Team members—Virgil Adderley, Mike Brett, Jay Davis, Ken Schiff, and John Stark—for guidance and review of this report.

Citation King County. 2017. Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal. Prepared by Timothy Clark, Wendy Eash‐Loucks, and Dean Wilson, Water and Land Resources Division. Seattle, Washington.

King County i October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table of Contents

Executive Summary ...... xii Acronyms and Abbreviations ...... xx 1.0 Introduction ...... 1–1 1.1 King County Wastewater System ...... 1–1 1.2 CSO Control Program ...... 1–3 1.3 Water Quality Assessment and Monitoring Study ...... 1–3 1.4 Scope and Content of this Report ...... 1–6 1.4.1 Sources and Quality of Data ...... 1–6 1.4.2 Interpreting Box Plots...... 1–7 2.0 Study Area ...... 2–1 2.1 Characteristics ...... 2–1 2.1.1 Morphology and Shoreline Development ...... 2–1 2.1.2 Hydrology and Circulation ...... 2–3 2.2 Historical Uses ...... 2–6 2.3 Current Uses ...... 2–7 2.4 Salmon in Lake Union/Ship Canal ...... 2–9 2.4.1 Salmon Stocks and Life History Characteristics ...... 2–9 2.4.2 Mortality ...... 2–10 2.5 EPA‐Approved Listed Impairments ...... 2–12 2.6 Sources and Pathways of Contamination ...... 2–12 2.6.1 Conceptual Site Model ...... 2–13 2.6.2 Major Ongoing Contaminant Sources and Pathways ...... 2–14 2.7 CSO Discharge Sites ...... 2–15 2.8 Stormwater Discharge Sites ...... 2–20 2.9 Planned and Completed Corrective Actions ...... 2–20 2.9.1 Historical Contamination Cleanup Areas ...... 2–20 2.9.2 U.S. Army Corps of Engineers Water Quality Study ...... 2–23 3.0 Water Quality ...... 3–1 3.1 Sampling Sites and Parameters ...... 3–1 3.2 Sampling and Analysis Methodologies ...... 3–3

King County ii October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

3.3 Bacteria ...... 3–5 3.3.1 Current Conditions ...... 3–5 3.3.2 Comparison to Criteria ...... 3–6 3.3.3 Long‐Term Trends ...... 3–9 3.4 Physical Parameters ...... 3–10 3.4.1 Temperature ...... 3–10 3.4.2 Salinity/Conductivity ...... 3–17 3.4.3 Dissolved Oxygen ...... 3–19 3.4.4 Turbidity/Total Suspended Solids/Secchi Transparency ...... 3–24 3.4.5 pH and Alkalinity ...... 3–27 3.5 Chlorophyll a ...... 3–32 3.5.1 Laboratory and Field Method Changes ...... 3–32 3.5.2 Current Conditions ...... 3–32 3.5.3 Long‐Term Trends ...... 3–35 3.6 Nutrients ...... 3–35 3.6.1 Nitrogen ...... 3–36 3.6.2 Phosphorus ...... 3–46 3.6.3 Silica ...... 3–52 3.7 Trophic State Indices and Limiting Factors for Phytoplankton ...... 3–55 3.7.1 Trophic State Indices ...... 3–55 3.7.2 Limiting Factors...... 3–59 3.7.3 Nitrogen to Total Phosphorus Ratio ...... 3–60 3.7.4 Phytoplankton Community and Biovolume ...... 3–61 3.8 Metals ...... 3–61 3.8.1 Methodology ...... 3–62 3.8.2 Current Conditions ...... 3–62 3.8.3 Comparison to Criteria ...... 3–66 3.9 Organic Chemicals ...... 3–68 3.9.1 Current Conditions ...... 3–68 3.9.2 Comparison to Criteria ...... 3–71 4.0 Sediment Quality ...... 4‐1 4.1 Mechanics of Sediment Contamination ...... 4‐1

King County iii October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

4.2 Sediment Porewater Salinity ...... 4‐2 4.3 Sediment Management Standards ...... 4‐2 4.3.1 Chemical Criteria ...... 4‐3 4.3.2 Biological Criteria ...... 4‐4 4.4 Data Sources and Methodology ...... 4‐5 4.5 Physical Structure of Sediments ...... 4‐14 4.6 Comparison of Chemical Concentrations to Criteria ...... 4‐17 4.6.1 Portage Bay and the Montlake Cut ...... 4–21 4.6.2 Lake Union ...... 4–22 4.6.3 Salmon Bay and the Fremont Cut ...... 4–23 4.7 Comparison of Bioassay Results to Criteria ...... 4–24 4.8 Chemicals without Numeric Criteria ...... 4–25 4.8.1 PBDEs ...... 4–25 4.8.2 Dioxin/Furans ...... 4–25 4.9 Benthic Macroinvertebrate Communities ...... 4–29 4.10 Summary ...... 4–31 5.0 Tissue Chemistry ...... 5–1 6.0 Findings and Data limitations ...... 6–1 6.1 Findings ...... 6–1 6.1.1 Water Quality ...... 6–1 6.1.2 Sediment Quality ...... 6–3 6.2 Next Steps in the Water Quality Assessment and Monitoring Study ...... 6–4 6.3 Potential Future Studies ...... 6–5 6.3.1 Data Limitations Directly or Indirectly Linked to CSO Impacts ...... 6–5 6.3.2 Other Data Limitations ...... 6–7 7.0 References ...... 7–1 Appendix A: Glossary ...... A‐1 Appendix B: Study Area ...... B‐1 Appendix C: Water Quality ...... C‐1 Appendix D: Metals and Organics Tables ...... D‐1 Appendix E: Sediment Quality ...... E‐1 Appendix F: Tissue Chemistry ...... F‐1

King County iv October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Appendix G: Phytoplankton in Lake Union/Ship Canal ...... G‐1 Appendix H: Saltwater Intrusion in Lake Union/Ship Canal ...... H‐1 Appendix I: Literature Review ...... I‐1

Figures

Figure 1‐1. King County’s wastewater treatment system...... 1–2 Figure 1‐2. Reports and study questions answered as part of the Water Quality Assessment and Monitoring Study...... 1‐6 Figure 1‐3. Explanation of parts of a typical box plot...... 1–8 Figure 2‐1. Lake Union/Ship Canal study area (shown in dark blue)...... 2–2 Figure 2‐2. Hydraulic residence time (HRT) in the Lake Union/Ship Canal study area by month based on outflow from the Ballard Locks (2002−2011) (King County, 2013). Black line indicates mean HRT of 9.9 days...... 2–4 Figure 2‐3. Generalized water circulation patterns in the Lake Union/Ship Canal study area...... 2–5 Figure 2‐4. Levels of development intensity in land use areas surrounding the Lake Union/Ship Canal study area...... 2–8 Figure 2‐5. Conceptual site model for Lake Union/Ship Canal showing major sources, pathways, and fates of contamination (adapted from King County, 2013). . 2–14 Figure 2‐6. CSO and stormwater outfalls and the sewer system in Lake Union/Ship Canal...... 2–16 Figure 2‐7. Sediment cleanup sites in the Lake Union/Ship Canal study area (source: Ecology, 2008)...... 2–21 Figure 3‐1. Locations of long‐term water quality monitoring sites in Lake Union/Ship Canal...... 3–2 Figure 3‐2. Fecal coliform bacteria concentrations at 1‐m depth at sites in Lake Union Ship Canal (2004–2013)...... 3–6 Figure 3‐3. Water quality criteria violations of fecal coliform bacteria in Lake Union/Ship Canal. An X denotes a high colony count but does not signify a violation...... 3–8 Figure 3‐4. Annual fecal coliform bacteria geomeans in Lake Union/Ship Canal (1976– 2013)...... 3–10 Figure 3‐5. Time‐depth isopleths of median monthly temperature at the Dexter‐SW Lake Union site (2009–2013)...... 3–11 Figure 3‐6. Surface temperature (0–5 m) in Lake Union/Ship Canal (2009–2013)...... 3–12

King County v October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3‐7. 7‐DADMax at USACE sites in Lake Union/Ship Canal (2004–2013). Ecology‐ defined core summer salmonid habitat is highlighted in yellow. Thermal stress threshold is shown as pink line, and direct mortality and thermal barrier threshold is shown as red line (source: USACE unpublished data). . 3–14 Figure 3‐8. Mean summer hypolimnetic temperatures at the Dexter‐SW Lake Union site (1985−2013). Regression slope = −0.138°C per year; p < 0.0001...... 3–16 Figure 3‐9. Time‐depth isopleths of median monthly salinity values at the Dexter–SW Lake Union site (2009–2013)...... 3–18 Figure 3‐10. Time‐depth isopleths of median monthly dissolved oxygen concentrations at the Dexter –SW Lake Union site (2009–2013)...... 3–20 Figure 3‐11. Dissolved oxygen concentrations at the (a) Locks–Salmon Bay and (b) Dexter–SW Lake Union sites (2004–2013). White boxes represent 1‐m samples; grey boxes represent 5‐m samples (Locks) and 14‐m samples (Dexter)...... 3–21 Figure 3‐12. Dissolved oxygen concentrations in the epilimnion in Lake Union/Ship Canal (2009–2013)...... 3–22 Figure 3‐13. Minimum dissolved oxygen (DO) concentrationns at King County monitoring sites in Lake Union/Ship Canal (2004–2013). Ecology‐defined core summer salmonid habitat is highlighted in yellow. Optimal minimum DO level is shown as green line, critical DO level is shown as pink line, and lethal DO level is shown as red line...... 3–23 Figure 3‐14. Secchi transparency in Lake Union/Ship Canal (2009–2013)...... 3–26 Figure 3‐15. Epilimnion (a) turbidity values (2004–2008) and (b) TSS values (2009– 2013) in Lake Union/Ship Canal...... 3–26 Figure 3‐16. Epilimnion pH values in Lake Union/Ship Canal (2009–2013)...... 3–28 Figure 3‐17. pH values in Lake Union/Ship Canal compared to water quality criterion (2004–2013). Red line represents surface pH; black line represents the bottom sample. Low and high ends of criterion range (6.5 and 8.5) are shown as solid lines. Ecology‐defined core summer salmonid habitat is hightlighted in yellow...... 3–30 Figure 3‐18. Chlorophyll a concentrations in Lake Union/Ship Canal (2009–2013)...... 3–33 Figure 3‐19. Monthly chlorophyll a concentrations in Lake Union/Ship Canal (2009– 2013)...... 3–34 Figure 3‐20. Generalized nitrogen cycle in fresh water (source: University of Michigan, 2014)...... 3–37 Figure 3‐21. Nitrate + nitrite‐N epilimnion concentrations in Lake Union/Ship Canal (2009–2013). Dashed line is the upper method detection limit (MDL); solid line is the lower MDL. Concentrations below MDL were generated using regression‐on‐order statistics...... 3–38

King County vi October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3‐22. Time‐depth isopleths of median monthly nitrate +nitrite‐N concentrations at the Dexter–SW Lake Union site (2009–2013)...... 3–39 Figure 3‐23. Epilimnion ammonia concentrations in Lake Union/Ship Canal (2009– 2013). Dashed line is the upper method detection limit (MDL); solid line is the lower MDL. Concentrations below MDL were generated using regression‐on‐order statistics...... 3–41 Figure 3‐24. Time‐depth isopleths of median monthly ammonia concentrations at the Dexter–SW Lake Union site (2009–2013). Note log‐scale...... 3–42 Figure 3‐25. Epilimnion total nitrogen concentrations in Lake Union/Ship Canal (2009– 2013)...... 3–44 Figure 3‐26. Time‐depth isopleths of median monthly total nitrogen concentrations at the Dexter–SW Lake Union site (2009–2013). Note log‐scale...... 3–45 Figure 3‐27. Orthophosphate epilimnion concentrations in Lake Union/Ship Canal (2009–2013). Dashed line is the upper method detection limit (MDL); solid line is the lower MDL. Values below the MDL were generated using regression‐on‐order statistics. Note log‐scale. Values in µg/L (mg/L*10‐3). 3–48 Figure 3‐28. Time‐depth isopleths of median monthly orthophosphate concentrations at the Dexter–SW Lake Union site (2009–2013). Note log‐scale...... 3–48 Figure 3‐29. Epilimnion total phosphorus concentrations in Lake Union/Ship Canal (2009–2013)...... 3–51 Figure 3‐30. Time‐depth isopleths of median monthly total phosphorus concentrations at the Dexter–SW Lake Union site (2009–2013). Note log‐scale...... 3–51 Figure 3‐31. Silica epilimnion concentrations in Lake Union/Ship Canal (2009–2013). . 3–54 Figure 3‐32. Monthly epilimnion silica concentrations at the Dexter–SW Lake Union site (2009–2013)...... 3–54 Figure 3‐33. Epilimnion spring (March – June) trophic state index at the Dexter–SW Lake Union site (1985–2013)...... 3–57 Figure 3‐34. Epilimnion summer (July – September) trophic state index at the Dexter– SW Lake Union site (1985–2013)...... 3–57 Figure 3‐35. Summer Trophic state index residuals for the Dexter–SW Lake Union site (1985–2013)...... 3–59 Figure 3‐36. Distribution of total metals in the epilimnion of Lake Union/Ship Canal and Shilshole Bay (2000–2008). Black solid line represents maximum method detection limit. Note log‐scale...... 3–64 Figure 3-37. Distribution of dissolved metals in the epilimnion in Lake Union/Ship Canal and Shilshole Bay 2000–2008). Solid black line repesents maximum method dectection limit. Note log‐scale...... 3‐65 Figure 3-38. Sampling locations for organic chemicals in Lake Union/Ship Canal (2000– 2004)...... 3.69

King County vii October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 4‐1. Schematic of processes controlling chemical concentrations in surface sediments in fresh water (source: Jacobs et al., 1988)...... 4‐2 Figure 4‐2. Location of sediment sampling sites and respective studies from Ecology’s Environmental Information Management system database. (See legend on following page.) ...... 4‐11 Figure 4‐3. Location and year ranges of sediment sampling sites from Ecology’s Environmental Information Management system database...... 4‐13 Figure 4‐4. Percent of fines (silt and clay) in sediment at sampling sites in Lake Union/Ship Canal...... 4‐15 Figure 4‐5. Percent of total organic carbon in sediment at sampling sites in Lake Union/Ship Canal...... 4‐16 Figure 4‐6. Number of exceedances of Sediment Management Standards at 375 sampling sites in Lake Union/Ship Canal and 17 sites in Union Bay. Dot size indicates number of criteria parameters measured...... 4‐20 Figure 4‐7. Bioassay data and comparison to Sediment Management Standards for sediment sampling sites in Lake Union/Ship Canal. Rose and teal colored slices in pinwheel legend indicate acute and chronic toxicity tests, respectively...... 4–27 Figure 4‐8. Sediment bioassay results compared to Sediment Management Standards for sediment sampling sites in Lake Union/Ship Canal...... 4–28

Tables

Table 2‐1. Morphometry of Lake Union/Ship Canal system...... 2–3 Table 2‐2. Salmon stocks in Cedar‐Sammamish watershed identified in the Salmonid Stock Inventory (WDFW, 2002; City of Seattle and USACE, 2008)...... 2–9 Table 2‐3. Salmon life history characteristics by species in the Cedar‐Sammamish watershed...... 2–10 Table 2‐4. Current (2012) EPA‐approved 303(d) list of pollutants not meeting water quality standards in Lake Union/Ship Canal...... 2–12 Table 2‐5. Water quality parameters likely altered by human activities in Lake Union/Ship Canal...... 2–13 Table 2‐6. Average annual discharge frequency and volume of King County CSOs in the Lake Union/Ship Canal study area and Union Bay (2009–2013)...... 2–18 Table 2‐7. Average annual discharge frequency and volume of City of Seattle CSOs in Lake Union/Ship Canal and Union Bay (2009–2013)...... 2–19

King County viii October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table 2‐8. Average annual CSO discharge volume into Lake Union/Ship Canal study area and Union Bay (2009–2013) and percent contributed by King County CSOs...... 2–20 Table 3‐1. Long‐term ambient water quality sites used for water quality analysis of Lake Union/Ship Canal...... 3–1 Table 3‐2. Concentrations (CFU/100 mL) of fecal coliform bacteria at 1‐m depth in Lake Union/Ship Canal (2004–2013)...... 3–5 Table 3‐3. Seasonal Mann‐Kendall trends for fecal coliform bacteria concentrations in Lake Union/Ship Canal...... 3–9 Table 3‐4. Temperature trends in Lake Union/Ship Canal determined through multivariate regression...... 3–15 Table 3‐5. Comparison of epilimnion and hypolimnion mean monthly temperatures and p‐values from two‐sided, two‐sample t‐test for two periods (1985– 1995 and 2004–2013) at the Dexter–SW Lake Union site. Values in bold indicate differences at a 0.05 level of significance...... 3–17 Table 3‐6. Seasonal Mann‐Kendall trends for volume‐weighted conductivity in Lake Union/Ship Canal...... 3–19 Table 3‐7. Seasonal Mann‐Kendall trends for volume‐weighted dissolved oxygen concentrations in Lake Union/Ship Canal...... 3–24 Table 3‐8. Secchi transparency and total suspended solids (2009–2013) and turbidity (2004–2008) in Lake Union/Ship Canal...... 3–25 Table 3‐9. Seasonal Mann‐Kendall trends for Secchi transparency in Lake Union/Ship Canal...... 3–27 Table 3‐10. Seasonal Mann‐Kendall trends in Lake Union/Ship Canal for volume‐ weighted pH based on hydrogen ion activity...... 3–31 Table 3‐11. Seasonal Mann‐Kendall trends for volume‐weighted alkalinity in Lake Union/Ship Canal...... 3–31 Table 3‐12. Chlorophyll a concentrations (µg/L) in Lake Union/Ship Canal (2009– 2013)...... 3–33 Table 3‐13. Seasonal Mann‐Kendall trends for chlorophyll a concentrations in Lake Union/Ship Canal...... 3–35 Table 3‐14. Nitrate + nitrite‐N concentrations (mg/L) in Lake Union/Ship Canal (2009– 2013)...... 3–38 Table 3‐15. Seasonal Mann‐Kendall trends for volume‐weighted nitrate + nitrite‐N concentrations in Lake Union/Ship Canal. Interquartile ranges for p‐values and slope magnitude from 1,000 permutations are presented...... 3–40 Table 3‐16. Ammonia concentrations (mg/L) in Lake Union/Ship Canal (2009–2013). 3–41

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Table 3‐17. Seasonal Mann‐Kendall trends for volume‐weighted ammonia concentrations. Interquartile ranges for p‐values and slope magnitude from 1,000 permutations are presented...... 3–43 Table 3‐18. Total nitrogen concentrations (mg/L) in Lake Union/Ship Canal (2009– 2013)...... 3–44 Table 3‐19. Seasonal Mann‐Kendall trends for volume‐weighted total nitrogen concentrations in Lake Union/Ship Canal...... 3–46 Table 3‐20. Orthophosphate concentrations (mg/L) in Lake Union/Ship Canal (2009– 2013)...... 3–47 Table 3‐21. Seasonal Mann‐Kendall trends for volume‐weighted orthophosphate concentrations in Lake Union/Ship Canal. Interquartile ranges for p‐values and slope magnitude from 1,000 permutations are presented...... 3–49 Table 3‐22. Total phosphorus concentrations (mg/L) in Lake Union/Ship Canal (2009– 2013)...... 3–50 Table 3‐23. Seasonal Mann‐Kendall trends for volume‐weighted total phosphorus concentrations in Lake Union/Ship Canal...... 3–52 Table 3‐24. Silica concentrations (mg/L) in Lake Union/Ship Canal (2009–2013)...... 3–53 Table 3‐25. Description of trophic state index (TSI) classifications...... 3–56 Table 3‐26. Spring and summer trophic state index value trends for total phosphorus, chlorophyll a, and Secchi transparency for the Dexter–SW Lake Union site (1985–2013)...... 3–58 Table 3‐27. Spring and summer trophic state index value trends for total phosphorus, chlorophyll a, and Secchi transparency for the Dexter–SW Lake Union site (1997–2013)...... 3–58 Table 3‐28. Molar Si:N and molar Si:P ratios at the Dexter–SW Lake Union site (2009– 2013)...... 3–60 Table 3‐29. Mass‐based total nitrogen to total phosphorus ratio by season at the Dexter–SW Lake Union site (2009–2013)...... 3–61 Table 3‐30. Detection frequency and maximum of metals concentrations (µg/L) in Lake Union/Ship Canal compared to Washington State and EPA water quality criteria...... 3–67 Table 3‐31. Number and frequency of detections for the 24 organic chemicals detected in Lake Union/Ship Canal (2000–2004)...... 3–70 Table 3‐32. Number and frequency of PAH detections and maximum detected and potential concentrations (µg/L) of total PAHs (ΣPAHs) in Lake Union/Ship Canal (2000–2004)...... 3–70 Table 3‐33. Total PCB and PBDE concentrations (pg/L) from the 2011–2012 high‐ resolution survey of two sites in Lake Union/Ship Canal...... 3–71

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Table 3‐34. Detection frequency and maximum concentrations (µg/L) of organic chemcials in Lake Union/Ship Canal compared to water quality criteria (2000–2004). Highest mean for a monitoring station is also provided. Exceedances of EPA Human Health Criteria are highlighted in red and of Washington State criteria in bold. Method detection limits above the state chronic criteria are in bold; limits above Human Health Criteria are highlighted in yellow...... 3–73 Table 4‐1. Freshwater Chemical Sediment Cleanup Objectives (SCOs) and Cleanup Screening Levels (CSLs) (dry‐weight basis)...... 4‐3 Table 4‐2. Freshwater Biological Sediment Cleanup Objectives (SCOs) and Cleanup Screening Levels (CSLs)...... 4‐5 Table 4‐3. Studies with surface sediment samples taken in Lake Union/Ship Canal at undredged/uncapped locations found in Ecology’s Environmental Information Management (EIM) system database...... 4‐7 Table 4‐5. Polybrominated diphenyl ether (PBDE) sediment concentrations (µg/kg‐ dw) at a site in central Lake Union (2010)...... 4–25 Table 4‐6. Dioxin/furan results (ng/kg‐dw) at four Lake Union/Ship Canal and one Union Bay sediment sampling site (2005). Laboratory qualifiers are provided...... 4–29 Table 4‐7. Benthic macroinvertebrate data from 15 sites in Lake Union/Ship Canal (2001)...... 4–30

King County xi October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

EXECUTIVE SUMMARY King County completed a study of the Lake Union/Ship Canal system in the heart of Seattle. The study employed data previously collected from a variety of monitoring studies to characterize existing water quality and other indicators of the system’s environmental health, evaluate long‐term trends, describe potential pathways of pollution, and identify limitations in current data. The study was prepared as part of a Water Quality Assessment and Monitoring Study, undertaken to explore ways to optimize water quality improvements in the three waterbodies where the County is planning combined sewer overflow (CSO) control projects—Elliott Bay, Lake Union/Ship Canal, and the Duwamish Estuary.

Background King County updates its combined sewer overflow (CSO) control plan about every five years. Before each update, the County reviews its entire CSO Control Program against conditions that have changed since the last update. In September 2012, the King County Council passed Ordinance 17413 approving an amendment to the long‐term CSO control plan. The plan includes nine projects to control the County’s remaining 14 uncontrolled CSOs by 2030. The recommended projects involve construction of underground storage tanks, green stormwater infrastructure, wet weather treatment facilities, or a combination of approaches.

Ordinance 17413 also calls for completion of a Water Quality Assessment and Monitoring Study to inform the next plan update due to the Washington State Department of Ecology in 2019. This study compiles existing information on water quality in Lake Union/Ship Canal to address one of the assessment’s study questions: “What are the existing and projected water quality impairments in receiving waters (waterbodies) where King County CSOs discharge?” As a part of the assessment, similar studies are being completed for Elliott Bay and the Duwamish Estuary. The final product of the assessment will be a synthesis report that summarizes the results of these studies and of other studies conducted to fill identified data gaps and analyze pollutant loadings to the three waterbodies.

Study Area The Lake Union/Ship Canal study area is divided into three sections: Salmon Bay, Lake Union, and Portage Bay (Figure ES‐1). It is surrounded by the City of Seattle. The system has undergone many changes in the past century. Current land use is a mixture of residential, commercial, and industrial development, with a small amount of undeveloped land. The shoreline is developed with docks, houseboats, and bulkheads; virtually no natural shoreline remains except in southern Portage Bay.

The study area forms the mouth of the Cedar‐Sammamish Watershed. The Cedar River enters the south end of Lake Washington, which drains through the Montlake Cut, Lake Union, the Fremont Cut, and the Hiram M. Chittenden Locks to Puget Sound (shown as

King County xii October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

“Ballard Locks” in the figure). The immediate Lake Union/Ship Canal drainage area (the area that does not drain to Lake Washington) is 24 square miles.

Lake Union/Ship Canal is the shipping route between Puget Sound and Lake Washington and supports some commercial activities. Humans may come in contact with the water in the system through recreational activities such as boating. Many species of salmon, including the endangered Puget Sound Chinook and coho salmon, must travel through the system as part of their migration to or from Puget Sound.

Figure ES-1. Lake Union/Ship Canal study area (shown in dark blue).

Sources and Pathways of Contamination The sewer infrastructure servicing the majority of the land surrounding Lake Union/Ship Canal is part of a combined system in which pipes carry both wastewater and stormwater to wastewater treatment plants. Most of the combined flows are treated before being discharged to Puget Sound. During heavy rain when volumes exceed the capacity of the combined sewers and treatment plants, excess flow discharges directly into Lake Union/Ship Canal as CSOs. There are 33 CSO outfalls in and near the Lake Union/Ship Canal study area (Figure ES‐2); 21 of these are controlled, meaning that only one overflow event occurs per year on a 20‐year moving average. King County operates two controlled outfalls,

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four uncontrolled outfalls, and one nearly controlled CSO outfall in the study area. The City of Seattle operates 18 controlled and 8 uncontrolled CSOs.

Some parts of the Lake Union/Ship Canal drainage area are served by partially separated sewer systems. In such systems, rooftop gutters drain to sanitary sewers and street runoff flows to storm drains that discharge directly to nearby surface waters. Figure ES‐2 shows the 47 known stormwater outfalls in the Lake Union/Ship Canal study area. The principal pollutants associated with CSO and stormwater discharges are pathogens, oxygen‐ depleting material, suspended solids, metals, organic chemicals, and nutrients.

Figure ES-2. Locations of CSO and stormwater outfalls in Lake Union/Ship Canal.

In addition to stormwater and CSO discharges, many other pathways may contribute contaminants to the area.1 Dock activity is an ongoing source of pollution, as well as the resuspension of contaminated sediments by large vessels. Other potential pathways include contaminated groundwater, oil spills, illegal chemical dumping, atmospheric deposition, and contamination from upstream sources in the Lake Washington watershed.

1 Pathways are the routes through which a contaminant moves from its source or other intermediate media (air, surface water, groundwater, or soil) to the study areas. A source is the object, such as pesticides and combustion of fossil fuels, that may initially release a contaminant to environmental media or release it in a form that can be mobilized and transported in an environmental pathway.

King County xiv October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Humans, threatened and endangered species, and other species that use the waters of Lake Union/Ship Canal are potentially at risk from both historical and ongoing sources and pathways of contamination. Water and sediments in the study area have been subject to years of discharges and spills from the shipping industry, wastewater pipes, stormwater outfalls, and other industrial discharges. These discharges, along with urbanization, have produced much of the historical contamination existing today. Table ES‐1 lists general historical and ongoing activities that have likely significantly altered the water quality of Lake Union/Ship Canal since the early 20th century.

Table ES-1. Water quality parameters likely altered by human activities.

Activity Bacteria Temperature Oxygen Dissolved pH Clarity Water Nutrients Metals Chemicals Organic Agriculture/livestock production X X X X X X Discharge of sewage and stormwater X X X X X X X Dredging/channelization/regrading X X X X Industrial/shipping activities X X X Logging X X X Note: Highlighted rows indicate major ongoing activities.

Findings The main water quality issues in Lake Union/Ship Canal are high bacteria concentrations, high temperatures in surface waters in the summer, and low dissolved oxygen concentrations, also in the summer. Both bis(2‐ethyl hexyl)phthalate (BEHP) and polychlorinated biphenyl (PCB) concentrations have been detected above the U.S. Environmental Protection Agency (EPA) Human Health Criteria under the National Toxics Rule at levels that may cause adverse effects to human health (cancer risk) through consumption of organisms. However, more water samples and fish and shellfish tissue samples are needed to determine whether BEHP and PCBs are a human health concern in Lake Union/Ship Canal. In addition, more data are needed on the seasonal and spatial variability of metals and organic chemical concentrations to fully evaluate their potential impact on water quality and human health.

Sediments in Lake Union/Ship Canal have been found to be contaminated with heavy metals, PCBs, polycyclic aromatic hydrocarbons (PAHs), tributyltin (TBT), phthalates, and other organic chemicals. Concentrations of these chemicals exceed the Washington State benthic cleanup levels for freshwater sediments. The sediments in Salmon Bay and near Gas Works Park in Lake Union contain hot spots of contamination interspersed with areas of more moderate concentrations. Sediment chemistry conditions in the study area may cause adverse effects for aquatic organisms. Salt water that enters the system from

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operation of the Locks can facilitate the release and resuspension of nutrients and contaminants from the sediments.

The following sections provide more detail on water and sediment quality findings.

Water Quality The most recent water quality conditions were evaluated using King County monthly and bimonthly data and U.S. Army Corps of Engineers hourly data from 2009 through 2013. When more than 10 years of data were available, long‐term trends were evaluated.

Major findings are as follows:  Bacteria. From a regulatory and human‐health standpoint, elevated bacteria concentrations (as measured by fecal coliforms) are a persistent water quality issue in Lake Union/Ship Canal and frequently exceed water quality criteria. Bacteria concentrations are typically highest near the Locks and decrease moving upstream, likely because the dominant circulation pattern in the system pushes the bacteria westward toward the Locks. However, bacteria concentrations have declined in the last several decades. CSO control and improved stormwater management may have contributed to this decline.  Temperature and dissolved oxygen. The high temperatures and low dissolved oxygen (DO) content in Lake Union/Ship Canal threaten salmonids and other aquatic life at certain times of the year. During the summer salmonid migration, temperatures of the top 10 m exceed thermal stress and direct mortality thresholds. By late summer, temperatures can exceed the thermal stress threshold even in the hypolimnetic (bottom) waters below 10 m. The stress is further intensified by DO conditions where hypolimnetic hypoxia/anoxia prevents adequate refuge from high water temperatures by making the cooler waters inhospitable. Over the past three decades, surface temperatures in Lake Union/Ship Canal have increased, summer hypolimnion temperatures have decreased, and thermal stratification has strengthened.  Salinity. The conditions in Lake Union/Ship Canal are substantially influenced by the intrusion of salt water via the Locks during the summer; the amount varies greatly year to year. Over the course of the summer, salinity along the bottom increases. A saltwater layer in some years may reach as far upstream as Portage Bay and Lake Washington. Saltwater pockets may remain in the deep holes of the Lake Union basin after Locks usage has decreased in the fall and winter, preventing mixing and prolonging anoxic and acidic conditions. Increased concentrations of metals, organic chemicals, and nutrients were observed near the lake bottom during an extended period of saltwater intrusion in 2002–2003. The influence of the saltwater layer on sediment chemistry and resuspension is the most likely cause of these increases.  Clarity. The clarity of Lake Union/Ship Canal is influenced by phytoplankton biovolume and inputs of particles from stormwater runoff and CSOs. Overall, transparency has increased or remained constant over the past 30 years.

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 pH and alkalinity. pH and alkalinity respond to biotic activity in Lake Union/Ship Canal. pH rises during the spring phytoplankton bloom, and acidic conditions appear in the hypolimnion as the result of decomposition of detritus during the summer and early fall. Levels occasionally exceeded the Washington State water quality criterion during the spring bloom.  Nutrient concentrations. Nutrient concentrations in Lake Union/Ship Canal are affected by inputs from Lake Washington and Union Bay via the Montlake Cut, from CSO and stormwater discharges, and from internal loading from sediments. Nutrient concentrations in the system have decreased over the years. The decreasing trends suggest that loading both from Lake Washington and the immediate Lake Union/Ship Canal watershed has decreased.  Chlorophyll a. Concentrations of chlorophyll a provide information on the level of phytoplankton productivity and biovolume in a lake. No substantial long‐term trends for chlorophyll a were observed from the mid‐1980s to present. Analysis of data from 1997 to present, however, indicates decreasing trends in spring and summer concentrations.  Phytoplankton growth and abundance. Phosphorus appears to be the most frequent limiting factor for phytoplankton growth and abundance. Nitrogen may be co‐limiting in the summer. The short hydraulic residence time of Lake Union/Ship Canal may limit phytoplankton buildup and abundance. Zooplankton grazing may also curb phytoplankton, but data are too limited to support this assumption. Phytoplankton communities are dominated by a spring bloom that features diatoms accompanied by cryptophytes to a lesser degree. Phytoplankton diversity peaks in the late summer when chlorophytes and cyanobacteria make up a greater portion of the overall population. A minor fall bloom, typically dominated by the diatom genera Tabellaria and Fragilaria, occurs in Lake Union.  Metals. The most recent metals data indicate that concentrations in Lake Union/Ship Canal have not exceeded the Washington State water quality criteria for aquatic life or the EPA Human Health Criteria. Concentrations of arsenic, copper, lead, mercury, nickel, and zinc were elevated in Salmon Bay near the Locks relative to the rest of Lake Union/Ship Canal. The Montlake Cut site had the lowest concentrations of these metals, suggesting that the metals are entering Lake Union/Ship Canal from the immediate watershed or from sediments.  Organic chemicals. The most frequent detections of organic chemicals occurred near the Locks site and in the hypolimnion in southwestern Lake Union. PAHs were detected most often in the hypolimnion, likely from resuspension of sediments. Detections of PAHs in the epilimnion (surface layer) suggest external loading and upward mixing from the hypolimnion. PCBs and BEHP were sometimes detected in the limited number of samples collected at concentrations exceeding EPA Human Health Criteria. Although data indicate that concentrations of other organic chemicals have not exceeded water quality criteria, the older samples typically had detection limits above many of the water quality criteria and data quality concerns. Little is known about contaminants of emerging concern, including many pharmaceuticals, pesticides, and flame‐retardants currently in use.

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Sediment Quality The analysis of available data found areas of elevated concentrations of contaminants in sediments throughout Lake Union/Ship Canal as the result of historical and/or currently operating outfalls and depositional sites.

Major findings are as follows:  The sediments of Salmon Bay and Lake Union are highly contaminated relative to Portage Bay, the Montlake Cut, and Lake Washington’s Union Bay in terms of both the number and magnitude of exceedances of Sediment Cleanup Standards under the Washington State Sediment Management Standards (SMS).  Bioassay analyses found that many sites in Salmon Bay and Lake Union are toxic. C. tentans was the most sensitive bioassay. The toxicity of the sediments near Gas Works Park in north Lake Union varied spatially and by study.  In Lake Union and Salmon Bay, the most widespread contaminants were metals (nickel, arsenic, mercury, silver, lead, copper, and chromium), TBT, total sulfides, total PAHs, phthalates, total PCBs, and dibenzofuran.  Significant sediment contamination, particularly PAH contamination, is present near Gas Works Park. The contamination is the result of historical operation of a gasification plant and leaching from contaminated upland soils.  Sediments in Portage Bay and the Montlake Cut were less contaminated than sediments in Salmon Bay and Lake Union. Exceedances of the SMS were found in Portage Bay and the Montlake Cut for total sulfides, cadmium, lead, mercury, silver, phthalates, and total PCBs, but unlike the remainder of Lake Union/Ship Canal, no exceedances were found for total PAHs.  Nearshore sediments and sediments near docks typically had higher concentrations of TBT, mercury, phthalate, PAHs, and carbazole than other sites.  Available data on the benthic macroinvertebrate community in Lake Union/Ship Canal indicate the following: o Benthos are predominately comprised of pollution‐tolerant taxa, exhibiting limited biodiversity. o The least impacted sites, as evidenced by the presence of pollutant‐sensitive and diverse benthos, are in southern Portage Bay, the west end of the Fremont Cut, and southeast Lake Union. o Benthos are more tolerant and less diverse compared to the benthos in Lake Washington and Lake Sammamish. Other Assessment Reports Other reports have been prepared as part of King County’s Water Quality Assessment and Monitoring Study:  Similar to this area report for Lake Union/Ship Canal, two reports document existing conditions and long‐term trends in two other study areas—Elliott Bay and the Duwamish Estuary.

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 A report documents the process used to assess identified data gaps for the study areas and select studies to fill prioritized gaps.  Three reports describe the methodology and results of three selected data gap studies: a study of bacteria in wet and dry weather, a survey of contaminants of emerging concern, and a literature review of potential conservative sewage tracers.  A loadings report discusses present‐day contributions of pollutants from various pathways, including stormwater and CSOs, into the study areas and evaluate water quality impairments.  A future loadings report assesses the potential of planned actions such as CSO control to improve water quality.  A synthesis (summary) report combines and discusses the results of these analyses.

King County will use the information from the Water Quality and Assessment Study to inform the next CSO control plan update, including looking for opportunities to improve water quality outcomes, possibly reduce costs of CSO control projects, establish baseline conditions for post‐construction monitoring of CSO control projects, and decide whether to pursue an Integrated Plan under EPA guidance. The information from the assessment can also be used to inform regional efforts to continue to improve water and sediment quality.

King County xix October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

ACRONYMS AND ABBREVIATIONS

µg microgram ANC acid neutralizing capacity ATP adenosine triphosphate BEHP bis(2‐ethyl hexyl)phthalate CEC contaminant of concern CFU colony‐forming unit CSL cleanup screening levels CSO combined sewer overflow DBT dibutyltin DDD dichlorodiphenyldichloroethane DDE dichlorodiphenyldichloroethylene DDT dichlorodiphenyltrichloroethane DO dissolved oxygen dw dry weight Ecology Washington State Department of Ecology EDC endocrine disrupting compound EIM Environmental Information Management system EPA Environmental Protection Agency ESA Endangered Species Act FOD frequency of detection HCH hexachlorocyclohexane HPAH high molecular weight polycyclic aromatic hydrocarbon HRT hydraulic residence time ICP‐MS Inductively Coupled Plasma Mass Spectrometry KCEL King County Environmental Laboratory LIMS Laboratory Information Management System Locks Hiram M. Chittenden Locks LPAH low molecular weight polycyclic aromatic hydrocarbon MBT monobutyltin MDL method detection limit MG million gallons MTCA Model Toxics Control Act NADA Non‐detects and data analysis

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NMFS National Marine Fisheries Service NOAA National Oceanic and Atmospheric Administration NPDES National Pollutant Discharge Elimination System NTU nephelometric turbidity unit PAH polycyclic aromatic hydrocarbon PBDE polybrominated diphenyl ether PCB polychlorinated biphenyl PCP pentachlorophenol PDO Pacific Decal Oscillation pg picogram ppb parts per billion ppm parts per million ppt parts per thousand QC quality control ROS Regression‐on‐order statistics SCO sediment cleanup objective SMS Sediment Management Standards SQS Sediment Quality Standards SVOC semi‐volatile organic compound TBT tributyltin TeBT tetrabutyltin TOC total organic carbon TP total phosphorus TSI trophic state index TSS total suspended solids USACE U.S. Army Corps of Engineers USFWS United States Fish and Wildlife Service WAC Washington Administrative Code WTD King County Wastewater Treatment Division

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King County xxii October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

1.0 INTRODUCTION This report summarizes existing information on water quality and other indicators of the environmental conditions of Lake Union and the Lake Washington Ship Canal (Lake Union/Ship Canal) in Seattle. The report was prepared as part of King County’s Water Quality Assessment and Monitoring Study. The study was undertaken to explore ways to optimize water quality improvements in waterbodies where the County is planning combined sewer overflow control projects.

The following sections describe King County’s wastewater system, its Combined Sewer Overflow Control Program, the Water Quality Assessment and Monitoring Study, and the scope and content of this report.

1.1 King County Wastewater System

King County owns and operates a regional wastewater system that serves 1.7 million people in a 420‐square‐mile area in Washington state. The area covers most of urban King County including Seattle, south Snohomish County, and a small portion of Pierce County (Figure 1‐1).

The wastewater system is the largest in the Puget Sound region. It includes over 350 miles of pipelines that collect wastewater from 34 local sewer utilities. The pipelines carry the wastewater to three regional treatment plants—West Point Treatment Plant in the city of Seattle, South Treatment Plant in the city of Renton, and Brightwater Treatment Plant in south Snohomish County—that treat and disinfect the wastewater before discharging it to Puget Sound. The County also owns and operates two local treatment plants in the city of Carnation and on Vashon Island.

Through the early 20th century, most cities constructed combined sewer systems to collect both wastewater and stormwater in the same pipes. The combined sewers carried untreated wastewater directly to waterbodies. Today, combined flows are sent to treatment plants before being directly discharged to waterbodies. Untreated overflows occur only at designated locations during heavy storms when flows exceed the capacity of sewers and treatment plants. These combined sewer overflows (CSOs) serve as constructed relief points to prevent sewer backups into homes and streets.

In King County’s regional wastewater system, combined sewers are located only in Seattle. Figure 1‐1 shows the combined sewer area. Portions of this area contain separated and partially separated sewers. King County owns and operates 39 and the City of Seattle 87 CSO locations in the city limits. The outfall pipes at these locations discharge wastewater diluted with stormwater to Puget Sound, the Duwamish River, Lake Union/Ship Canal, and Lake Washington during large storms. On average over the long term, about 350 CSOs occur from King County locations each year. Average annual volumes at these locations can be as low as zero at one location to over 200 million gallons (MG) at another; the total average annual volume discharged from all county locations is about 800 MG.

King County 1–1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 1-1. King County’s wastewater treatment system.

King County 1–2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

1.2 CSO Control Program

CSO control is required by Washington state and federal law. “Control” means reducing the number of untreated overflows from each location to once per year on a 20‐year moving average. Controlling CSOs protects public health and the environment. CSO discharges are more concentrated with harmful chemicals and disease‐causing organisms than stormwater alone.

Since the regional wastewater system began operating in the 1960s, the County and City of Seattle have reduced the volume of untreated sewage discharges from around 30 billion gallons to less than 2 billion gallons a year. King County alone has invested $389 million to reduce its CSO volumes from 2.3 billion gallons in the 1980s to about 1 billion gallons today. It is investing another $117 million on projects that are under way. Only 14 of the County’s and about half of the City’s locations still require control. The County’s uncontrolled sites are located in the Duwamish River, Elliott Bay, and Lake Union/Ship Canal.

King County updates its CSO control plan about every five years. Before each update, the County’s Wastewater Treatment Division (WTD) reviews its entire CSO Control Program against conditions that have changed since the last update—conditions such as population and flow, scientific developments, regulations, new technologies, and public priorities. The latest CSO Control Program review and plan update was completed in 2012. As a result, the King County Council approved an amendment in September 2012 to the County’s long‐term CSO control plan through Ordinance 17413. The U.S. Environmental Protection Agency (EPA) also approved the plan in 2013, and the plan is incorporated into the consent decree that the County entered into with the U.S. Department of Justice, EPA, and the Washington State Department of Ecology (Ecology) in 2013.

The CSO control plan includes nine projects to control the remaining 14 uncontrolled CSOs by 2030. The recommended projects involve construction of underground storage tanks, green stormwater infrastructure, and/or wet weather treatment facilities. Four projects are in the Lake Union/Ship Canal area and five in the Duwamish Estuary and Elliott Bay areas. Ordinance 17413, approving the plan, also calls for completion of a Water Quality Assessment and Monitoring Study to inform the next plan update, which is due to regulators in 2018. In September 2013, the County Council approved the assessment’s scope of work through Motion 13966.

1.3 Water Quality Assessment and Monitoring Study

Work began in 2013 on the Water Quality Assessment and Monitoring Study. The objective of the assessment is to help ensure that investments in CSO control optimize water quality improvements in CSO sub‐basins. It includes a comprehensive scientific and technical analysis of existing water quality of the receiving waters where uncontrolled county CSOs

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discharge (Elliott Bay, Lake Union/Ship Canal, and the Duwamish Estuary), identification of water quality impairments, trends in water quality, assessment of sources contributing to impairments, and review of ongoing and planned activities to improve water quality. WTD will use the information to inform the 2018 CSO control plan update, prioritize and sequence CSO control projects, establish baseline conditions for post‐construction monitoring of CSO control projects, and decide whether to pursue an integrated plan based on EPA guidelines.

An integrated planning process has the potential to identify efficiencies in implementing competing requirements that arise from separate wastewater and stormwater projects, including capital investments and operation and maintenance requirements. This approach can build partnerships among agencies and jurisdictions and can lead to more sustainable and comprehensive solutions, such as green stormwater infrastructure, that improve water quality and support other attributes that enhance the vitality of communities.

The Water Quality Assessment and Monitoring Study sets out to generate information that will help answer the following study questions: 1. What are the existing and projected water quality impairments in receiving waters (waterbodies) where King County CSOs discharge?2 2. How do county CSOs contribute to the identified impairments? 3. How do other sources contribute to the identified impairments? 4. What activities are planned through 2030 that could affect water quality in the receiving waters? 5. How can CSO control projects and other planned or potential corrective actions be most effective in addressing the impairments? 6. How do various alternative sequences of CSO control projects integrated with other corrective actions compare in terms of cost, schedule, and effectiveness in addressing impairments? 7. What other possible actions, such as coordinating projects with the City of Seattle and altering the design of planned CSO control projects, could make CSO control projects more effective and/or help reduce the costs to WTD and the region of completing all CSO control projects by 2030?

An external Scientific and Technical Review Team has been assembled to review methodology and results. A synthesis report will incorporate the results of the analyses, data gap studies, and additional assessments to evaluate how to maximize water quality benefits from CSO improvements. Depending on assessment findings, the King County Council may decide to approve formation of an Executive's Advisory Panel of approximately 10 regional leaders. The panel would develop independent recommendations to the King County Executive on how planned county CSO control projects can best be sequenced and integrated with other projects to maximize water quality gains and minimize costs to ratepayers.

2 “Impairments” is defined as water quality‐related concerns.

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Table 1‐1 shows elements of the assessment and their associated study questions, deliverables, and estimated timeframes. Figure 1‐2 illustrates the flow of reports and how they will inform the CSO program review process. More information on the assessment is available at http://www.kingcounty.gov/environment/wastewater/CSO/WQstudy.aspx.

Table 1-1. Elements of the Water Quality Assessment and Monitoring Study. Element Applicable Deliverable Timeframe Study Question Review and analyze existing scientific and 1 Area reports: 2013–2017 technical data on impairments in Lake  Elliott Bay Union/Ship Canal, Duwamish Estuary, and  Lake Union/Ship Canal Elliott Bay.  Duwamish Estuary Conduct targeted data gathering and 2,3 Data gap study selection 2014–2017 monitoring to fill some of the identified gaps in report scientific data on water quality in these receiving waters. Data gap study reports:  Bacteria  Contaminants of emerging concern  Literature review of conservative sewage tracers Identify and quantify the current (2015) 2,3 Loadings Report 2015–2017 pathways of contaminants into the receiving waters.

Identify changes in contaminant loadings 1,2,3,4 Future Loadings Report 2015–2017 between 2015 and 2030, including the potential impact of planned corrective actions on identified impairments in the waterbodies. Summarize scientific and technical data 1,2,3,4 Synthesis Report 2015–2017 collected and reviewed during the assessment.

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Study Questions 1- Report on process 4: How county to select Study • Three CSOs and other additional studies Questions 1-4: reports on sources contribute • CSO • Reports on three existing to impairments, Control new studies: data: and planned Program • Lake corrective activities • Bacteria Sources • Synthesis review Union/Ship • Contaminants of Report process Canal Emerging • Summary • Elliott Bay • Loadings Concern and Study • Duwamish Reports • Method to Trace Analysis Questions 5-7: Estuary Sewage Effective CSO sequences Study Question 1: Study Questions 2-3: Existing How county CSOs impairments and other sources contribute to impairments

Figure 1-2. Reports and study questions answered as part of the Water Quality Assessment and Monitoring Study.

1.4 Scope and Content of this Report

The County owns seven CSO outfalls in Lake Union/Ship Canal. Two are controlled, one is undergoing modifications to achieve control, and four are scheduled to be controlled by 2030. This “area” report documents existing information on water quality in Lake Union/Ship Canal. It answers one of the assessment’s study questions: “What are the existing and projected water quality impairments in receiving waters (waterbodies) where King County CSOs discharge?” Similar reports are being produced for Elliott Bay and the Duwamish Estuary (including the East and West waterways).

1.4.1 Sources and Quality of Data King County and other agencies have collected data on water quality, sediment chemistry, and fish and shellfish tissue in Lake Union/Ship Canal. These data were evaluated and summarized as a part of this assessment in order to describe current conditions, identify long‐term trends, and review compliance with Washington State standards. Water column data included physical parameters (temperature, dissolved oxygen, salinity/conductance, pH, turbidity, and total suspended solids), chlorophyll a, nutrients, fecal coliform bacteria, metals, and various groups of organic compounds. Data on metals and organic compounds in sediments and fish/shellfish tissue were also analyzed.

Current water quality conditions were assessed using the last five years of data (2009– 2013) to capture inter‐annual variability while avoiding data that may not reflect the current state. The exception was in cases where parameters were added or removed, significant method detection changes occurred over time, or the most recent data for particular parameters dated from before 2009. Because of the intrinsic volatility of fecal coliform concentrations, data from 2004 through 2013 were used in order to better

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interpret and discuss the most recent conditions. Sites with over 10 years of data were evaluated for long‐term trends. Trend analyses were conducted over different timeframes because of changes in the location of sites monitored and lack of sufficient data at some sites to confidently detect trends.

Sediment data from a total of 40 studies in Lake Union/Ship Canal were reviewed; these studies include two recent King County sediment monitoring studies and multiple routine and compliance monitoring projects conducted by various agencies and private entities. These studies and projects included 405 geographically distinct sites in Lake Union/Ship Canal and 17 geographically distinct sites in Union Bay that act to provide upstream background conditions.

To account for inconsistencies in the data, media‐ or parameter‐specific considerations are discussed and data collection dates are given prior to presentation of results. Some parameters have been consistently monitored over the years as part of the County’s routine monitoring program. Other parameters were monitored as part of short‐term projects with different sample collection techniques, analytical methods, and overall data quality. Detection limits for parameters may vary substantially based on changes in analytical techniques and instrumentation between sampling events. In addition, the number of samples analyzed may vary for each study and parameter.

Data are summarized throughout this report. Raw data can be obtained by contacting [email protected].

1.4.2 Interpreting Box Plots Much of the data in this report are displayed in box plots, which show the spread of data for a parameter and differences at various locations. Figure 1‐3 describes each part of a typical plot. Letters above the boxes denote the statistical differences between sites; sites sharing the same letter are not statistically distinguishable at the alpha = 0.05 level of significance. Sites that do not share a letter are significantly different at the alpha = 0.05 level of significance.

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Samples with the same letter are not significantly different 6 from one another at alpha = 0.05 BC C 95th Percentile BC 5 90th Percentile AB 75th Percentile A 4 Median

3 25th Percentile

2 10th Percentile 5th Percentile Concentration of Parameter (units)

1 Samples with different letters are significantly different from one another at alpha = 0.05 0

Site 1 Site 2 Site 3 Site 4 Site 5 Site Figure 1-3. Explanation of parts of a typical box plot.

King County 1–8 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

2.0 STUDY AREA This chapter describes the general characteristics of the Lake Union/Ship Canal study area, its historical and current uses, sources of pollution, wastewater and stormwater discharge sites, and historical contamination cleanup sites. Additional information, including historical aerial photos, bathymetry, and a map of the watershed, appears in Appendix B. 2.1 Characteristics The Lake Union/Ship Canal study area is divided into three sections: Salmon Bay, Lake Union, and Portage Bay (Figure 2‐1). Salmon Bay is defined as the freshwater region between the Fremont Cut and the Ballard Locks. The study area is bordered by the city of Seattle on all sides. Water quality conditions in Lake Washington’s Union Bay were not assessed for this report.

The study area has undergone many changes in the past century, including changes to morphology and hydrology. It is bordered by a mixture of residential, commercial, and industrial development, and a small amount of undeveloped land. Docks, houseboats, and bulkheads occupy the shoreline; virtually no natural shoreline exists (Weitkamp et al., 2000). The morphology and hydrology of lakes influence the abiotic and biotic conditions in the water and sediments.

2.1.1 Morphology and Shoreline Development Before construction of the Lake Washington Ship Canal in 1917, Lake Union, Lake Washington, and Puget Sound were distinct waterbodies. The Ship Canal project included construction of the following:  Montlake Cut, which connects Portage Bay of Lake Union to Union Bay of Lake Washington  Fremont Cut, which connects Lake Union to Salmon Bay  Hiram M. Chittenden Locks (Locks) at the outlet of Salmon Bay into Puget Sound’s Shilshole Bay, which allow for the passage of ships and fish and also regulate the mixing of salt water and fresh water The project substantialy altered the hydrology of the Lake Washington system. Lake Washington’s outlet was changed from the Black River at the south end of the lake to the Montlake Cut, and the level of the lake dropped by approximately 3 m.

The Locks regulate the level of Lake Union and Lake Washington to about 6.7 m above sea level during May through August and about 6.1 m during the rest of the year. A navigation channel is maintained to a depth of 9 m in the canals and bays between Union Bay and the Locks. Lake Union is separated by a 13‐m sill into north and south basins that have depths of 14 m and 16 m, respectively (Rattray et al., 1954).

King County 2–1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 2-1. Lake Union/Ship Canal study area (shown in dark blue).

The morphometry of the Lake Union/Ship Canal system is presented in Table 2‐1. Features of each section of the study area are as follows:  The Lake Union basin represents the majority of the surface area and volume of the system. More than 95 percent of the shoreline is protected by bulkheads or riprap. The 323 overwater structures include multiple large industrial docks, boat marinas, and houseboat marinas (City of Seattle, 2010). The northern shore is bordered by Gas Works Park.  Portage Bay is predominately shallow. Its shoreline is highly urbanized and bordered by the University of Washington, residential development including numerous houseboats on the shoreline, marinas, and other water‐dependent businesses. More than 80 percent of the shoreline is armored. There are also 117 overwater structures (City of Seattle, 2010). The southern shoreline is unarmored and borders the City’s Montlake Playfield, which includes wetlands.  Salmon Bay is a shallow waterbody except for a deep region near the Locks that is approximately 15‐m deep. Its shoreline is 98 percent armored and contains a nearly continuous series of overwater structures (154 structures), including Fisherman’s Terminal and other commercial and industrial docks and marinas. On both shores,

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commercial and industrial uses with high amounts of impervious surfaces extend to the shoreline. Vegetation is limited, and the few street trees in the area are separated from the shoreline (City of Seattle, 2010).

Table 2-1. Morphometry of Lake Union/Ship Canal system. Surface Area Volume Mean Depth Max. Depth Area (105 m2) (106 m3) (m) (m) Salmon Bay and 10.4 5.6 5.4 14.6 Fremont Cut Lake Union 22.6 23.4 10.4 15.8 Portage Bay and 5.9 3.1 5.2 9.8 Montlake Cut Total 38.9 32.1 8.3 15.8

2.1.2 Hydrology and Circulation Lake Union/Ship Canal forms the mouth of the Cedar‐Sammamish watershed. The total area of the watershed is 9,880square miles. It contains two major rivers that drain to Lake Washington (Edmondson, 1977; King County, 2003a):  The Sammamish River, which drains Lake Sammamish and tributaries, enters Lake Washington from the north and provides about 30 percent of the inflow to lake.  The Cedar River enters the south end of the lake and contributes about 50 percent of the total inflow. Lake Washington drains through the Montlake Cut to Lake Union/Ship Canal. The water then passes through the Locks to Puget Sound. The contribution of water from the immediate Lake Union/Ship Canal watershed (the area that does not drain to Lake Washington) is small relative to the inflow from Lake Washington; the water from this local watershed generally enters as surface runoff and through stormwater and CSO outfalls (Tomlinson et al., 1977). The immediate watershed is 20 square miles. A major tributary to Lake Union/Ship Canal is the Densmore Drain; a system of pipes transports baseflows and stormflows from the Densmore basin (a 4.3 square‐mile urban area), Green Lake overflow, and stormwater from I‐5 near the Ravenna neighborhood to an outfall on the northern shore of Lake Union’s northeast arm west of the I‐5 bridge.

Washington State defines a lake as a waterbody with a mean residence time of 15 days (WAC 173‐201A‐020). However, Tomlinson et al. (1977) estimated Lake Union’s flushing rate as 52 times per year (a residence time of 7 days). A more recent analysis, based on a daily water balance that included storage, determined that the mean annual flow through Lake Union/Ship Canal is 1.2*109 m3 (King County, 2013), which yields a mean hydraulic residence time (HRT) for the entire Lake Union/Ship Canal system of 9.9 days (a flushing rate of 36.7 times per year). Figure 2‐2 displays the HRTs for the Lake Union/Ship Canal study area for each month for the years 2002 through 2011. A greater flushing rate occurs when the U.S. Army Corps of Engineers (USACE) lowers the spillway gate at the Locks to 20 feet (6.1 m) above sea level in the fall and wetter weather returns in the winter and spring.

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During periods of sustained dry and warm weather, water movement drops by over 90 percent and Lake Union/Ship Canal’s flushing rate greatly decreases and the HRT increases (Tomlinson et al., 1977). Thus, the HRT of Lake Union/Ship Canal is greater in the summer during low flow conditions (averaging 26 to 30 days) and lower in the late fall and early winter during higher flow conditions (averaging 5 to 7 days). The HRTs of Salmon Bay and of Portage Bays are relatively short, averaging 1.7 and 0.9 days, respectively. These duration estimates do not consider circulation patterns; much of the flow may circumvent the Lake Union basin, isolating its southern waters and increasing their residence time.

Figure 2-2. Hydraulic residence time (HRT) in the Lake Union/Ship Canal study area by month based on outflow from the Ballard Locks (2002−2011) (King County, 2013). Black line indicates mean HRT of 9.9 days.

The circulation patterns of Lake Union/Ship Canal are highly variable and are determined by wind and the amount of salt water entering the system via the Locks, volume of inflow from Lake Washington, and strength of lake stratification (City of Seattle, 1994). From the few water circulation studies completed (Driggers, 1964; CH2M HILL, 1975; Metro, 1987), three main circulation patterns can be inferred:  The most common water circulation pattern is dominated by water flowing into Lake Union from Lake Washington through the Montlake Cut into Portage Bay and northern Lake Union. Water flows from east toward the west/northwest and out of the lake through the Fremont Cut (Figure 2‐3).  Circulation in Lake Union is dominated by a north‐to‐south movement. Water flow is toward the southern end of the lake where water is entrained before exiting through the Fremont Cut.  During periods of low inflow and quiescent weather, minimal circulation in the lake may occur.

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Figure 2-3. Generalized water circulation patterns in the Lake Union/Ship Canal study area.

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The circulation patterns in southern Lake Union have not been well‐characterized. Generally, water will exit through the Fremont Cut to the northwest, but the residence time is unknown. Depending on the circulation pattern, the waters in southern Lake Union may be isolated from the dominant flow and experience a prolonged residence time relative to the waters in northern Lake Union. The waters of southern Portage Bay, Fisherman’s Terminal, and northwest Salmon Bay may be similarly isolated from the dominant flow pattern.

During the summer when flow from Lake Washington and the local watershed are at a minimum and the use of the Locks are at maximum, large quantities of salt water may overwhelm the capacity of the saltwater barrier and drain at the Locks, causing a saltwater wedge to accumulate east of the Locks in Salmon Bay. Without mixing by strong winds, the cold, dense salt water moves through the Fremont Cut to Lake Union and possibly to Portage Bay and Lake Washington. 2.2 Historical Uses This section summarizes the historical uses of Lake Union/Ship Canal. For more information, see Tobin (1986).

The original inhabitants of Lake Union were Native Americans affiliated with the Duwamish tribal group, which was part of the Puget Sound Salish peoples. David Denny was the first white settler to lay claim on Lake Union in 1850. The first major industrial use of Lake Union was the shipment of coal in the 1870s. Brickmaking was another early industry along the lake. In 1882, a lumber mill was constructed at its southern end. Sawdust from the mill was dumped into the lake. A landfill eventually covered the small bay at the lake's southwest corner.

In 1906, the Seattle Lighting Company built a gas plant on the north shore of Lake Union. Originally, the facility was a coal‐compressing plant. Gas was generated at the plant from the high‐temperature cooking of coal. The plant emitted steam and oily wastes, and tar and sludge accumulated as waste byproducts. Production ended in 1956, when natural gas piped from the southwest became available. The gas plant was one of the worst polluters of Lake Union (Foster, 1943). It discharged carcinogenic polycyclic aromatic hydrocarbons (PAHs) into the lake that adsorbed to the bottom sediments. The substantial amount of oil in the water caused fish kills.

Foster (1943) identified two other major sources of pollution to Lake Union/Ship Canal— the Lake Union Steam Plant and Fishermen's Terminal:  The Lake Union Steam Plant was built by Seattle City Light in 1914. Its primary effect on water and sediment pollution was the introduction of polychlorinated biphenyls (PCBs) from the oil used in its electrical transformers. The plant was decommissioned in 1987. It has since been remodeled and now houses ZymoGenetics, a biotechnology laboratory.

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 The Seattle Port Commission established Fishermen’s Terminal in Salmon Bay in 1913. Discharges of wood scraps, oil wastes, bilge sludge, and metal trimmings have resulted from marine boat moorage and repair at the terminal. The problem was exacerbated by the density of activity in the small area. Fisherman’s Terminal is now a certified Clean Marina, practicing marina best management practices such as prohibiting oil discharges and providing sewage and bilge pump‐out facilities (http://www.cleanmarinawashington.org/). However, some incidental discharge has since been observed as visible oil sheens on the water’s surface (Ecology, 2015). The completion of the Lake Washington Ship Canal in 1917 furthered the industrialization of Lake Union/Ship Canal by allowing transport between calm fresh waters to Puget Sound. The onset of each world war spurred additional industrial growth in the area. Industries included shipbuilders and boatyards, asphalt plants, a Ford Motors assembly plant, and coal, lumber, wood product, wool, brick, canning, and laundry companies. By the 1930s, sand and gravel industries were the dominant bulk materials handling companies. In the postwar years, the Shilshole Bay waterfront remained mostly industrial, with shipbuilding and repair, fishing moorage, fish processing, plywood, and metal product industries. 2.3 Current Uses The majority of land use surrounding Lake Union/Ship Canal is urban (Figure 2‐4). Most industry in the study area is found along Salmon Bay and the Fremont Cut, and mid‐density residential and commercial developments are found along the shores of Lake Union and Portage Bay. Commercial and industrial marinas are common throughout the system. More than 400 houseboats and floating homes reside on Lake Union and Portage Bay. In 1967, the City of Seattle required that houseboats connect to the sewer system to mitigate wastewater discharge to these waterbodies. The 0.5‐square‐foot Gas Works Park, site of the former Seattle Lighting Company gas plant, is on the northern shore of Lake Union, and the Port of Seattle’s Fisherman’s Terminal, a commercial and recreational boat moorage site, remains active in Salmon Bay.

Lake Union/Ship Canal is the only shipping route between Puget Sound and Lake Washington. The system is heavily used recreationally by motorized craft and sailboats, in addition to kayaking, paddle‐boarding, rowing, and other low‐speed activities. Lake Union provides a landing and takeoff strip for commercial floatplanes. Because of the legacy of sediment pollution, no swimming beaches exist on Lake Union. However, swimming and other direct contact activities occur regularly. In the recently redeveloped South Lake Union Park, a beach designated for canoe launching has been adopted as an informal swimming beach. Limited data exist on fish catch and consumption rates in Lake Union/Ship Canal, but fishing activity has been observed (King County, 2003b).

King County 2–7 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 2-4. Levels of development intensity in land use areas surrounding the Lake Union/Ship Canal study area.

King County 2–8 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

2.4 Salmon in Lake Union/Ship Canal

The Cedar‐Sammamish watershed is home to Chinook, coho, and sockeye salmon; steelhead; and rainbow, cutthroat, and bull trout. Salmon and some trout and char are anadromous; they spawn and rear in fresh water and mature in salt water. Because the study area serves as the mouth of the Cedar‐Sammamish watershed, all anadromous salmonids must pass through Lake Union/Ship Canal and the Locks as they out‐migrate as juveniles to Puget Sound and return as mature adults to spawn in their natal streams. Salmon die after spawning. Anadromous trout may pass between the freshwater and marine environments and spawn more than once.

2.4.1 Salmon Stocks and Life History Characteristics Many stocks of wild salmonid populations in the Puget Sound ecoregion have declined.3 In March 1999, the National Marine Fisheries Service (NMFS) listed Puget Sound Chinook salmon as a threatened species under the Endangered Species Act (ESA). In November 1999, the U.S. Fish and Wildlife Service (USFWS) listed bull trout as a threatened species under the ESA. Wild salmon and trout populations in the Cedar‐Sammamish watershed are augmented by hatchery fish. Table 2‐2 lists individual salmon stocks in the watershed and the influence of hatchery‐raised fish on the stock (WDFW, 2002; City of Seattle and USACE, 2008).

Table 2-2. Salmon stocks in Cedar-Sammamish watershed identified in the Salmonid Stock Inventory (WDFW, 2002; City of Seattle and USACE, 2008). Salmon Stock Hatchery Influence Species Cedar River Approximately one-third of returning adults are hatchery fish. Chinook Sammamish River Stock includes hatchery and naturally produced fish. Coho Cedar River Minimal hatchery influence. Hatchery releases ended in 1970. Cedar River Stock includes hatchery and naturally produced fish. Lakes Washington and Mostly naturally produced fish. Sockeye Sammamish tributaries Lake Washington Natural production (originated from Baker Lake plantings). beach spawning Steelhead Cedar River Natural production. Hatchery plants existed from 1933 to 2001.

Table 2‐3 summarizes life history characteristics of salmon in the Cedar‐Sammamish watershed. Salmon species in the watershed differ in the timing and areas they use for spawning, rearing, and migration. The timing of Chinook and sockeye adult in‐migration and chinook smolt out‐migration overlaps with peak summer water temperatures. The first part of the adult coho in‐migration period overlaps with high temperatures in August and September. High temperatures may cause pre‐spawning mortality or sublethal effects. Steelhead migration does not overlap with peak summer water temperatures.

3 Stocks are groups of same species fish that differ from other groups in how and when they use habitat.

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Table 2-3. Salmon life history characteristics by species in the Cedar-Sammamish watershed. Characteristic Chinook Sockeye Coho Steelhead Escapement (number reaching freshwater spawning grounds)a 78,000 (2004– Mean (years) 2,600 (2004–2013) 870 (1998–2006) 12.4 (2004–2013) 2013) Lowest (year) 1500 (2011) 13,500 (2009) 250 (2006) 0 (2012) Migration timing for return to natal streams Duration June–Sept. June–July Aug.–Nov. Jan.–May Peak Aug. Early July Sept. Feb. 4.05 days Time spent in Lake 4 hours – 8 days (average; Newell Unknown Unknown Union/Ship Canal (average: 1 day) and Quinn, 2005) Spawning Duration Aug.–Nov. Oct.–Dec. Oct.–Feb. March–Sept. Peak Oct. Oct.–Nov. Nov.–Dec. May Tributaries, Mainstem, Primary habitat Mainstem Mainstem mainstem tributatries Emergence Late May – early Duration Jan.–June Jan.–April March–April Aug. Peak Feb.–March March–April March July Freshwater Residence Lake, littoral, Tributaries, rivers, Habitat Lake, limnetic Tributaries, rivers limnetic lake, limnetic Duration (years) < 1 0.5–2.3 1.5 2 Outmigration timing Duration May–Sept. April–June April–July April–June Peak June May May May Time spent in Lake 2–4 weeks < 1 week < 2 weeks Unknown Union/Ship Canal Marine residence (years) Range 2–5 1–3 0.5–1.5 2–3 Most common 4 2 1.5 2–3 a Escapement data from Washington State Department of Fish and Wildlife (WDFW, 2015)

2.4.2 Mortality Mortality has been observed at the Locks for upstream migrating adult sockeye salmon, primarily during years with high summer temperatures. In 1998 and 2004, observers noted dead sockeye salmon near the Locks and in Lake Union/Ship Canal, including dozens to hundreds of dead adult sockeye in late July 2004 during peak water temperatures. During the record high temperatures in 1998, dead pre‐spawned Chinook were observed in Lake Union/Ship Canal.

The Synthesis of Salmon Research and Monitoring report compiled recent research on natural‐ and hatchery‐origin salmonids in Lake Union/Ship Canal, Union Bay, and Shilshole

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Bay (Seattle and USACE, 2008). The report discusses smolt and adult salmonid habitat, behavior, and survival risks. Major conclusions are presented below.

Salmon Smolt  Lake Union/Ship Canal o Chinook smolts appear to move along lake shorelines while out‐migrating, lingering mid‐channel and in littoral areas. o Juvenile Chinook salmon appear to avoid overwater structures while migrating by moving into deeper water to swim around the piers. The large number of overwater structures may substantially influence juvenile Chinook behavior in Lake Union/Ship Canal. o Juvenile Chinook often hesitate before entering at the Montlake Cut, possibly because of the lack of shallow water habitat. o Elevated water temperatures may also influence juvenile salmon out‐ migration, especially the later out‐migrating Chinook. o Dominant predators are northern pike minnow, largemouth bass, cutthroat trout, and piscivorous (fish‐eating) birds. The impact of predation has not been studied.  Passage through the Locks o The primary routes through the Locks for juvenile salmon are the spillway/smolt flumes and large and small locks. o Passage at the Locks by young‐of‐year Chinook and sockeye smolts may be initiated in response to the lunar apogee or quarter moon. o The large lock and associated filling culverts are thought to be the second most frequent route for smolts through the Locks. Fish may become entrapped in the filling culverts, exposing them to descaling and other harm.

Adult Salmon  Passage through the Locks o Most adult salmon return through the fish ladder or the large lock chambers, fewer use the saltwater drain, not many use the small lock, and none use the flumes. o Most adult Chinook, coho, and sockeye pass through the fish ladder during the day. Few pass at night. o Adult Chinook may hold up to 19 days in the cool water refuge above the Locks. Sockeye and coho do not hold in that area as long. Adults holding at the Locks appear to be choosing their location based on temperatures, dissolved oxygen levels, and water velocity.

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o High water temperatures in the fish ladder may alter route choice for adult Chinook salmon and may be associated with lower returns to Lake Washington. o High temperatures and low dissolved oxygen upstream of the Locks may inhibit adult salmon movement away from the cool water refuge.  Passage through Lake Union/Ship Canal o Adult Chinook average 1 day in Lake Union/Ship Canal, with total time ranging from 4 hours to 7.7 days. o En‐route mortality has been observed in Lake Union/Ship Canal in years of high summer temperatures, particularly for adult sockeye. The cause is unknown.

2.5 EPA-Approved Listed Impairments

The federal Clean Water Act, adopted in 1972, requires that all states restore their waters to be “fishable and swimmable.” Section 303(d) of the Clean Water Act established a process to identify and clean up polluted waters. Every two years, all states are required to assess the quality of surface waters in the state, including all rivers, lakes, and marine waters where data are available.

Waters whose beneficial uses (such as drinking, recreation, aquatic habitat, and industrial use) are impaired by pollutants are placed in the polluted water category on the water quality assessment. These waterbodies fall short of state surface water quality standards and are not expected to improve within the next two years. The 303(d) list, so called because the process is described in Section 303(d) of the Clean Water Act, includes waters in the polluted water category.

The current (2012) EPA‐approved 303(d) listing of impairments in Lake Union/Ship Canal is presented in Table 2‐4. Changes proposed for the 2014 listings are noted.

Table 2-4. Current (2012) EPA-approved 303(d) list of pollutants not meeting water quality standards in Lake Union/Ship Canal. Media Parameter Listing ID Bacteria 12172 Aldrin 11918 Watera Lead 8066 Total phosphorusb 52844 Sediment Sediment bioassay 500016 a Temperature is included in the draft 2014 Water Quality Assessment and Candidate 303(d) list submitted to EPA (Lake Union/Ship Canal: 79039). b Removed in draft 2014 Water Quality Assessment and Candidate 303(d) list submitted to EPA.

2.6 Sources and Pathways of Contamination Humans, threatened/endangered species, and other species that use the waters of Lake Union/Ship Canal are potentially at risk from both historical and ongoing sources and pathways of contaminants. Water and sediments in the study area have been subject to

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years of discharges and spills from the shipping industry, wastewater pipes, stormwater outfalls, and other industrial discharges. Along with urbanization, these sources and pathways have produced much of the historical contamination existing today. Table 2‐5 presents general historical and ongoing human activities that have likely altered the water quality parameters of Lake Union/Ship Canal since the early 20th century.

Table 2-5. Water quality parameters likely altered by human activities in Lake Union/Ship Canal.

Activity Bacteria Temperature Oxygen Dissolved pH Clarity Water Nutrients Metals Organic Pollutants Agriculture/livestock production X X X X X X Discharge of sewage and stormwater X X X X X X X Dredging/channelization/regrading X X X X Industrial/shipping activities X X X Logging X X X Note: Highlighted rows indicate major ongoing activities.

2.6.1 Conceptual Site Model Figure 2‐5 shows a conceptual site model for the Lake Union/Ship Canal study area that identifies the major sources, pathways, and fates for contamination. These include upstream flow from Lake Washington, long‐range transport of airborne contaminants directly deposited to the water surface or in the watershed, watershed drainage contributing to surface water via stormwater or CSO discharges and groundwater transport. Once contaminants are introduced, a number of processes determine their mass (and concentration) in water and sediments. The processes include gas exchange across the air‐water interface, diffusion across the sediment‐water interface, settling and resuspension, burial in deep sediments, and washout through the Locks.

Some contaminants, such as PCBs and polybrominated diphenyl ethers (PBDEs), may enter the food web through accumulation in phytoplankton at the base of the food web, through uptake directly from the water, and through accumulation by sediment‐dwelling organisms (benthos). Contaminant concentrations can then increase with each increase in trophic level (biomagnify) posing the greatest risk to fish‐eating animals, including humans, river otters, and birds.

Circulation patterns and vessel traffic corridors likely influence the distribution of contaminants in the water column and sediments. Depositional rates could be lower in high flow velocity and vessel traffic areas, such as the Fremont and Montlake cuts, than in low flow and vessel traffic areas, such as south Lake Union.

King County 2–13 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 2-5. Conceptual site model for Lake Union/Ship Canal showing major sources, pathways, and fates of contamination (adapted from King County, 2013).

2.6.2 Major Ongoing Contaminant Sources and Pathways This section describes major ongoing sources and pathways of pollution into Lake Union/Ship Canal. More detail on CSO and stormwater discharges is presented in the section that follows.

Sources and pathways are as follows:  Leaching of historical contaminants from polluted soil sites. Groundwater may be contaminated as it passes through polluted soils (Turney and Goerlitz, 1990). Recent groundwater surveys of Gas Works Park have found high levels of PAHs and volatile organic compounds (GeoEngineers, 2013). The loading of pollutants via groundwater into Lake Union/Ship Canal has not been quantified.  Densmore drainage basin input. The outflow from Green Lake is combined with stormwater from the Densmore drainage basin and a portion of I‐5 (Herrera, 2003). The pipe outlet is located in northeast Lake Union/Portage Bay. Green Lake is eutrophic and can produce toxic algal blooms.4  Vessel discharge and runoff. Houseboats, watercraft, and other lake usage may discharge pollutants, such as sewage, paint, gasoline, oil, and cleaning detergents. Most boats used in marine waters have hulls coated with soft toxic paints that are ablative or sloughing to keep aquatic organisms from attaching. These toxic chemicals can be released when the paint is disturbed or cleaned. Additionally, ballast and bilge water from vessels entering through the Locks may be a source of metals, oil, fuel, and other pollutants.

4 A eutrophic lake is characterized by an abundant accumulation of nutrients that support a dense growth of algae, the decay of which depletes the shallow waters of oxygen in summer.

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 Resuspension of contaminated sediments. The resuspension of the sediments through wave action, vessel propeller mixing (propwash), dredging, biotic perturbation, or other physical disturbances may increase environmental exposure to contaminants in the sediments.  Lake Washington influent. King County (2013) found that Lake Washington influent was responsible for 57 percent of total PCB loadings into Lake Union/Ship Canal and 83 percent of total PBDE loadings. Lake Washington is mesotrophic (having a moderate amount of dissolved nutrients) (King County, 2003a).  Atmospheric deposition. Deposition of trace metals and organic compounds that are bound to dust particles contribute contaminants to Lake Union/Ship Canal. Atmospheric deposition contributes an estimated 2 percent of total PCB loadings into the system and 3 percent of PBDE loadings (King County, 2013). Atmospheric deposition of mercury, lead, nitrogen, phosphorus, hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethane (DDT), PCBs, and PAHs has also been measured in urban and rural lakes across the United States (Swain et al., 1992; Jassby et al., 1994; EPA, 2014a).  CSO and stormwater discharges. CSO and stormwater discharges carry contaminants from sewage, domestic and industrial waste, fertilizers, pesticides, and other sources related to watershed activities and development. The discharges are regulated through National Pollutant Discharge Elimination System (NPDES) permits issued to King County and the City of Seattle. The City is responsible for stormwater outfalls; both the City and County are responsible for their respective CSO outfalls. The following sections describe CSO and stormwater discharge sites in the study area.

2.7 CSO Discharge Sites

The land surrounding the Lake Union/Ship Canal study area is served by combined and partially separated sewer systems (Figure 2‐6). Combined sewers carry both wastewater and stormwater in the same pipes to wastewater treatment plants; in partially separated systems, home gutters drain to the sanitary sewer and runoff from streets flows to storm sewers.

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Figure 2-6. CSO and stormwater outfalls and the sewer system in Lake Union/Ship Canal.

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CSOs may potentially harm aquatic ecosystems, impact human use, and pose other public health and environmental concerns. The following constituents may be found in CSOs:  Pathogens (disease‐causing bacteria, viruses, and parasites)  Oxygen‐depleting material (organic matter)  Suspended solids, which can hamper sight‐feeding fish and bury habitat  Toxins, including copper, endocrine‐disrupting compounds, and pesticides  Nutrients (phosphorus and nitrogen), which may cause eutrophication and toxic algal blooms Of the 33 CSO outfalls located in Lake Union/Ship Canal, 26 are maintained by the City of Seattle and 7 by King County. Nine of the Seattle CSOs are uncontrolled and 17 are controlled. Four county CSOs are uncontrolled, two are controlled, and one (Dexter Ave CSO) is undergoing adjustments to optimize performance and achieve full control. King County plans to bring all its CSOs into control by 2030 through storage, green stormwater infrastructure, treatment, and improved conveyance. The City of Seattle approved an Integrated Plan to be completed by 2025 (City of Seattle, 2015a and b). The plan includes both CSO control and stormwater management projects.

This section describes King County CSO locations in more detail as background to aid this Water Quality Assessment and Monitoring Study in examining water quality and guiding decisions for sub‐basins where uncontrolled county CSOs discharge.

The seven County CSOs in Lake Union/Ship Canal, from west to east, are as follows.  Ballard. The Ballard CSO discharges from outfalls on the north side of Salmon Bay in Ballard. As of 2014, the Ballard CSO is considered controlled through construction of a new 7‐foot‐wide sewer pipe under Salmon Bay between the Ballard and Interbay areas of Seattle. The new pipe partners with two 3‐foot‐wide wooden pipes (Ballard Siphons) built in the 1930s to serve north Seattle. On most days, combined sewage flows through the older pipes and on to the West Point Treatment Plant. The new pipe stores extra flow during storms when the older pipes are full.  11th Ave NW. The 11th Ave NW CSO site, located on the north side of the Fremont Cut at the east end of Salmon bay, is scheduled to be controlled either through a King County project that would construct 3,200 feet of 84‐inch‐diameter pipe by 2030 to convey flows to the Ballard Siphons or through a joint project with the City of Seattle that would construct a storage tunnel on the north side of the Fremont Cut by about 2025 that would control two county (11th Ave NW and 3rd Ave W) and four city CSO sites. In addition, green stormwater infrastructure will be implemented in the basins to enhance CSO control.5

5 Green stormwater infrastructure improvements include green streets and alleys in the public right‐of‐way and the RainWise Program that gives rebates for installing rain gardens and cisterns on private property.

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 Canal St. The Canal St CSO site, located on the north side of the Fremont Cut, is the forebay to the Fremont Siphon. The site is considered controlled through system design and operation.  3rd Ave W. The 3rd Ave W CSO site, located on the south side of the Fremont Cut, is the aftbay to the Fremont Siphon. The site will be controlled either through a joint county‐city 7.23‐MG storage tank on the north side of the Fremont Cut that would also control three city CSO sites or through a county 4.18‐MG storage tank on the south side of the Ship Canal, both scheduled for completion in 2023. Control could also be achieved through the joint project described above for the 11th Ave W CSO.  Dexter Ave. Since its completion in 2005, the Mercer Tunnel stores combined flows that would otherwise discharge through the Dexter Ave CSO. If tunnel capacity is exceeded before flows can be sent to the West Point Treatment Plant, the stored flows are treated at the Elliott West wet weather treatment facility, which discharges to Elliott Bay. This system has substantially decreased CSOs from the Dexter Ave CSO site, and the County is making system adjustments to achieve full control (King County, 2012a).  University. The University CSO discharges from the east side of Portage Bay. Control will be achieved by 2028 either through a joint county‐city 5.23‐MG storage tank that would also control three city CSO sites or through a county project that would construct a 2.94‐MG storage tank. In addition, green stormwater infrastructure will be implemented in the basin to enhance CSO control.  Montlake. The Montlake CSO discharges from the south side of the Montlake Cut. Control will be achieved by 2028 either through a joint county‐city 7.87‐MG storage tank that would also control three city North Union Bay CSO sites or through a county project that would construct a 6.6‐MG storage tank. Green stormwater infrastructure will be implemented in the basin to enhance CSO control. Tables 2‐6 and 2‐7 present average 2009–2013 annual discharge volumes and frequencies for county and city CSOs in the study area. Data for Union Bay of Lake Washington are included because of the bay’s proximity to the Montlake Cut. County CSOs contribute 70 percent of the annual volume to Lake Union/Ship Canal (excluding Union Bay) (Table 2‐8). Discharge from the County’s Montlake and University CSOs constitute nearly all the volume entering Portage Bay and the Montlake Cut. Seattle CSOs contribute about two‐thirds of the volume discharged to Lake Union and two‐thirds to Salmon Bay and the Fremont Cut.

Table 2-6. Average annual discharge frequency and volume of King County CSOs in the Lake Union/Ship Canal study area and Union Bay (2009–2013). Average Average CSO Location Frequency Volume (MG) Controlled?a Ballard Salmon Bay 8.0 1.1 Yes Salmon Bay/ 11th Ave NW 16.6 11.1 No Fremont Cut Canal St Fremont Cut 0.6 0.3 Yes 3rd Ave W Fremont Cut 8.4 9.4 No Dexter Ave Lake Union 10.2 7.7 Nearb Montlake Montlake Cut 9.2 34.5 No

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Average Average CSO Location Frequency Volume (MG) Controlled?a University Portage Bay 8.0 77.2 No Belvoir Union Bay 0.8 1.1 Yes a Control status is determined through calculation of a 20‐year moving average. b The Dexter Ave CSO will be fully controlled through system adjustments that are under way.

Table 2-7. Average annual discharge frequency and volume of City of Seattle CSOs in Lake Union/Ship Canal and Union Bay (2009–2013). CSO Average Average Number Location Frequency Volume (MG) Controlled?a 16 Union Bay 0.2 1.2 Yes 18 Union Bay 5.4 6.6 No 19 Union Bay 0.2 Trace Yes Montlake 20 Yes Cut 2.6 0.6 22 Union Bay 2 0.3 Yes 120 Lake Union 0 0 Yes 121 Lake Union 0 0 Yes 124 Lake Union 0 0 Yes 127 Lake Union 0.2 Trace Yes 129 Lake Union 0.4 Trace Yes 130 Lake Union 0 0 Yes 131 Lake Union 0 0 Yes 132 Lake Union 0.6 Trace Yes 134 Lake Union 0 0 Yes 135 Portage Bay 0.2 Trace Yes 136 Portage Bay 0 0 Yes 138 Portage Bay 2 0.5 No 139 Portage Bay 1.4 0.2 No 140 Portage Bay 5.2 0.3 No 141 Portage Bay 0 0 Yes 144 Lake Union 0 0 Yes 145 Lake Union 0 0 Yes 146 Lake Union 0 0 Yes 147 Lake Union 44.4 16.0 No Fremont 148 Yes Cut 0.6 Trace 150/151 Salmon Bay 24.2 3.0 No 152 Salmon Bay 48.2 33.0 No Fremont 174 No Cut 12.2 7.0 175 Lake Union 0.6 Trace Yes a Control status is determined through calculation of a 20‐year moving average.

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Table 2-8. Average annual CSO discharge volume into Lake Union/Ship Canal study area and Union Bay (2009–2013) and percent contributed by King County CSOs. Average Percent from King Region Volume (MG) County CSOs Salmon Bay and Fremont Cut 64.9 33.7 Lake Union 23.7 32.5 Portage Bay and Montlake Cut 111.3 98.6 Union Bay 9.2 12.0 Total (excluding Union Bay) 201.9 70.0

2.8 Stormwater Discharge Sites

Stormwater runoff from yards, roads, and sidewalks discharges directly into the waterbody in the partially separated areas surrounding much of north side of Salmon Bay, the Fremont Cut, and Portage Bay and the south side of the Lake Union basin (see Figure 2‐5). The City of Seattle owns most of the stormwater outfalls in the study area; public agencies and private industries own the other outfalls.

There are 47 known stormwater outfalls that discharge into Lake Union/Ship Canal (see Figure 2‐6). The City’s NPDES stormwater permit requires the complete mapping of all stormwater pipes over 8 inches in diameter and all outfalls greater than 24 inches in diameter; this effort is under way (City of Seattle, 2014).

Stormwater runoff from I‐5 as far north as north of Green Lake is channeled to the same pipes that convey drainage from the Densmore basin and overflow from Green Lake. This effluent is discharged west of the I‐5 bridge on the north shore of Lake Union’s northeast arm. Additional runoff from I‐5 and stormwater from a portion of the Capitol Hill neighborhood enter southeastern Lake Union at Broadway and Fairview.

An estimated 1.4 billion gallons of stormwater enter the system from city of Seattle outfalls each year (Herrera & Brown and Caldwell, 1994). This estimate does not include drainage from Green Lake and the Densmore basin. Runoff from highway bridges over Lake Union/Ship Canal contributes an additional estimated annual volume of 24.7 million gallons (King County, 2013). 2.9 Planned and Completed Corrective Actions The following sections describe cleanup of historical contamination in Lake Union/Ship Canal and work that USACE is undertaking to improve water quality in the area. Other planned corrective actions will be discussed in the future loadings report prepared for this Water Quality Assessment and Monitoring Study.

2.9.1 Historical Contamination Cleanup Areas Ecology has identified 10 sites in the study area, totaling over 100 acres on mostly state‐ owned aquatic lands, where sediments are contaminated as a result of historical maritime

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and industrial activities (Figure 2‐7). Five sites—three in Lake Union and two in Salmon Bay—are awaiting cleanup. Four Lake Union sites are in early stages of cleanup, and one site has completed the cleanup process. Contaminants of concern include low levels of bioaccumulative contaminants, in particular tributyltin (TBT) and PCBs (Ecology, 2008). The following sections describe the Lake Union sites that are undergoing or have completed cleanups.

Figure 2-7. Sediment cleanup sites in the Lake Union/Ship Canal study area (source: Ecology, 2008).

Gas Works Park Gas Works Park is a 20‐acre site located on the north shore of Lake Union. The park extends into the lake. From the early 1900s until 1956, the Seattle Gas Light Company operated a plant at the site that converted coal and oil into manufactured gas. The American Tar Company operated a tar refinery nearby that produced coal tar–based products by refining materials obtained as a byproduct of the gas manufacturing process.

The uplands portion of the site underwent an environmental cleanup in 2000 and 2001, in which 2 feet of clean topsoil was placed over a protective barrier. A groundwater remediation system was installed and operated from 2001 through 2006. Offshore sediment investigations found high levels of PAHs. Under an agreed order with Ecology, the

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City of Seattle and Puget Sound Energy are conducting remedial investigations and feasibility studies for these contaminated sediments. In‐water cleanup of contaminated sediments is expected to begin in 2017.

Metro Lake Union The 3‐acre Metro Transit Facilities North and Former Chevron Bulk Petroleum Terminal Number 100‐1327 site (“Metro Lake Union”) is located on the north side of Lake Union, west of Gas Works Park. Standard Oil of California (later renamed Chevron) constructed facilities in 1925–1927 and operated a diesel and bulk fueling and storage facility for several decades. Metro Transit purchased the facility in 1982 and operated a fueling station until 1989.

Groundwater and soils were contaminated with benzene, naphthalene, arsenic, cadmium, chromium, lead, mercury, and other pollutants. King County and Chevron entered into a consent decree with Ecology in 1999 under the state Model Toxics Control Act (MTCA). Cleanup work is scheduled for completion in 2015, followed by compliance monitoring to confirm that cleanup standards have been met.

Northlake Shipyard The Northlake Shipyard site is along the north shore of Lake Union near the Metro Lake Union site. Sediments were contaminated with total PAHs, PCBs, and metals, including antimony, arsenic, cadmium, copper, lead, mercury, nickel, silver, and zinc, from years of sandblasting and other work performed by Marine Power and Equipment Corporation.

Northlake Shipyard purchased the site and, as a part of the purchase agreement, entered into a consent decree with Ecology to clean up the sediments. Over 12,000 cubic yards of sediment were dredged from around the western pier and beneath the dry docks, and a 6‐ inch cap of clean sand was placed over the area. During dredging, 23 tons of large debris including logs, cables, and sections of vessels were removed. Work was completed in early 2014.

John Dunato & Co., Inc. Dunato’s Boatyard is along the north shore of Lake Union’s northeastern arm. The company entered into a voluntary cleanup agreement with Ecology for both an upland site and 5 acres of sediments surrounding its docks. PAHs, metals, and petroleum products in the sediments are at levels exceeding the Ecology standard, and additional organic compounds are suspected to be above the standard. Cleanup is under way.

Seattle City Parks NW Seaport The Seattle City Parks NW Seaport site is in southern Lake Union. Southern Lake Union was the site of various industries, including dry docks, a mill, machine shops, an asphalt plant, and commercial laundries. The site contains 3.4 acres of sediments that have been found to exceed Ecology PAH, PCB, metals, and benthic bioassay standards. The City of Seattle

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conducted remedial investigations and feasibility studies for these contaminated sediments, and cleanup has started.

2.9.2 U.S. Army Corps of Engineers Water Quality Study USACE conducted a study of potential methods to address salinity, temperature, and dissolved oxygen issues in Lake Union/Ship Canal. The study was done under Section 7 of the ESA to assess the effects of operation and maintenance of the Ship Canal on threatened Puget Sound Chinook salmon, Puget Sound steelhead, and Coastal/Puget Sound bull trout and on designated critical habitat for Chinook and bull trout (USACE, 2012a). An expert panel submitted nine recommendations to USACE in 2012. Ultimately, these recommendations seek to decrease summer water temperatures and increase summer dissolved oxygen concentrations for the benefit of migrating salmonids. Currently, USACE is investigating the feasibility and benefits of these recommendations.

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3.0 WATER QUALITY Various agencies have collected water quality data in Lake Union/Ship Canal, including King County, Ecology, USACE, and the University of Washington, often as part of long‐term monitoring programs. Only King County and USACE have datasets available for analyses of current conditions. This chapter describes the results of the analyses of these datasets in terms of current conditions, long‐term trends, and potential ecological and human health concerns regarding water quality in Lake Union/Ship Canal. The discussion is presented under the following categories: bacteria, physical parameters, chlorophyll a, nutrients, limiting factors, trophic state indices, metals, and organics.

3.1 Sampling Sites and Parameters

Water quality monitoring programs in Lake Union/Ship Canal are as follows:  Since the mid‐1970s, King County has monitored water quality at five sites for the following parameters each month: fecal indicator bacteria (total fecal coliforms), temperature, conductivity, dissolved oxygen (DO), turbidity, total suspended solids (TSS), pH, chlorophyll a, pheophytin a, total alkalinity (acid neutralizing capacity), and nutrients (ammonia‐N, nitrate + nitrite‐N, total nitrogen, total phosphorus, orthophosphate phosphorus, and silica). Not all parameters have been consistently monitored for the entire length of the program.  Short‐term programs have measured additional parameters in the water column such as metals and organics.  Since 2000, USACE has operated five monitoring sites in Lake Union/Ship Canal. These USACE stations collect hourly data for temperature, conductivity, and salinity at three or four discrete depths, depending on the site (USACE, 2004). The King County and USACE long‐term monitoring sites are described in Table 3‐1 and shown in Figure 3‐1. Discrete King County data are available by request to the lead author. USACE data are available at http://www.nwd‐wc.usace.army.mil/cgi‐bin/dataquery.pl.

Table 3-1. Long-term ambient water quality sites used for water quality analysis of Lake Union/Ship Canal. Agency Max. Depths and Depth at Sampled Years Locator Name and Description Northing Easting Site (m) (m) Sampled Locks–Salmon Bay (East King County of Ballard Locks in 1975– 0512 Salmon Bay) 246408 1255339 8 1, 5 present Fremont–NW Lake Union (West of Fremont Bridge King County at juncture of Lake Union 1974– 0518 and Fremont Cut) 239969 1266598 11 1, 9 2009 Dexter–SW Lake Union King County (Lake Union near Dexter 1, 5, 10, 1979– A522 Ave CSO outfall) 234484 1269458 16 14 present

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Agency Max. Depths and Depth at Sampled Years Locator Name and Description Northing Easting Site (m) (m) Sampled King County NE Lake Union–Portage 1975– 0536 Bay (under I-5 Bridge) 241871 1273447 9 1, 3 2008 King County Montlake Cut (near 1975– 0540 Montlake CSO outfall) 239584 1277624 11 1, 8 present 5.5, 8.2, USACE 11.0, 2000– LLLW Large Locks 246513 1255207 13 12.8 present USACE 3.4, 6.4, 2000– BBLW Ballard Bridge 246480 1255924 10 9.8 present USACE 5.5, 9.4, 2000– FBLW Fremont Bridge 239158 1267863 12.5 12.2 present USACE 1.2, 3.4, 2000– GWLW Gas Works 237727 1271568 11.5 7.6, 11.0 present USACE 1.8, 6.4, 2000– UBLW University Bridge 241817 1274400 11 10.7 present USACE = U.S. Army Corps of Engineers.

Figure 3-1. Locations of long-term water quality monitoring sites in Lake Union/Ship Canal.

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3.2 Sampling and Analysis Methodologies

This section describes general sampling and analysis procedures. Variances from these procedures are described in sections devoted to specific parameters. The methods employed by the King County Environmental Laboratory (KCEL) are described below. The monitoring and analysis plan for the USACE sites is published elsewhere (USACE, 2004).

The KCEL field unit measured conductivity, temperature, pH, and DO in the field using a calibrated Hydrolab® unit equipped with electronic sensors and lowered to selected depths. Transparency was measured using a 28‐cm‐diameter black‐and‐white Secchi disk equipped with a graduated line.

Grab samples for other parameters were collected at various depths in the water column using a Van Dorn sampler and analyzed by KCEL. Quality assurance/quality control procedures included the use of blanks, duplicates, and spikes. All data were reviewed by KCEL staff before entry into the Laboratory Information Management System (LIMS) database.

For this Lake Union/Ship Canal analysis, concentrations from samples taken at multiple depths in the same lake stratum at the same site were grouped to summarize a parameter. For example, nutrient concentrations observed from samples taken at 1‐ and 5‐m depths at the Locks–Salmon Bay site were grouped because both depths are in the surface layer (epilimnion). Sampling depths at all King County sites, except the Dexter–SW Lake Union site, are in the epilimnion. The Dexter–SW Lake Union site has one sampling depth in the bottom layer (hypolimnion).

Average volume‐weighted concentrations of selected parameters were calculated for Dexter–SW Lake Union to determine concentrations for the entire Lake Union basin for each sampling event. The volumes of the epilimnion and hypolimnion were determined by using the mean thermocline depth and lake bathymetry. To calculate the volume‐weighted concentration, the mean concentration of samples taken in the epilimnion was multiplied by the epilimnion volume and the product was added to the mean concentration of samples taken in the hypolimnion multiplied by the hypolimnion volume; this sum was then divided by the whole‐lake volume (epilimnion plus hypolimnion) to determine the average volume‐ weighted concentration over the water volume.

Investigations of the seasonality of water quality parameters defined seasons as follows:

Season Month Summer July–September Fall October–December Winter January–March Spring April–June

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Data Below the Method Detection Limit Concentrations below the method detection limit (MDL) were observed with regularity for some parameters, such as ammonia, nitrate +nitrite, orthophosphate, and many metals and organic compounds. These non‐detects are considered censored. The Kaplan‐Meier method was used to estimate the mean for left‐censored data sets because it does not require an assumption for the distribution of the parameter (Kaplan and Meier, 1958; Betchal Jacobs Company, 2000; Helsel, 2005a; Helsel, 2005b).

Values for parameters with the presence of non‐detects were compared between sites and depths using the Peto & Peto modification of the Gehan‐Wilcoxon test. Values for parameters without non‐detects were compared using the nonparametric Kruskal‐Wallis and Mann‐Whitney tests.

The cenboxplot script from the NADA package was used to develop box plots of censored datasets (Lee, 2013). This script plots the outcome of a regression‐on‐order statistics (ROS), which approximates the distribution of a dataset by plotting the detected values on a probability plot and calculating the linear regression. The ROS method assumes normal or lognormal distribution and requires a detection rate of at least 50 percent.

Sites Excluded from Characterization of Current Conditions The Fremont–NW Lake Union and NE Lake Union–Portage Bay sites were not included in the characterization of current conditions (2009 through 2013) because King County’s monitoring program stopped sampling at these sites after 2009 and 2008, respectively.

Long-Term Trend Analysis Long‐term trends were analyzed for parameters with at least 10 years of data.

For ammonia‐N, nitrate + nitrite‐N, and orthophosphate, a process of multiple imputations (substitution) was used because of the number of censored data points. Values below detection limits were replaced with randomly generated values based on a log‐normal distribution function calculated using maximum likelihood estimators. Seasonal Mann‐ Kendall tests for monotonic trends were applied to 1,000 iterations of imputation. Three‐ day cumulative precipitation was used as a covariate and month as the block group. Interquartile ranges for p‐values and Theil‐Sen slopes were reported, and the third quartile p‐value was used as the statistic for conservatively determining the significance of nitrogen trends.

Because bacteria, conductivity, DO, Secchi depth, pH in terms of hydrogen ion activity, alkalinity, total nitrogen, and total phosphorus had few or no censored data points, seasonal Mann‐Kendall tests for monotonic trends were used with three‐day cumulative precipitation as a covariate and month as a block group. The Mann‐Kendall test is rank‐ based and thus can tolerate a small percentage of censored data.

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For temperature and trophic state indices, linear regressions were used for determining trends. A multivariate linear regression was employed for temperature.

3.3 Bacteria

Fecal coliform bacteria are generally found in the intestinal tracts and feces of humans and other warm‐blooded animals. They may enter Lake Union/Ship Canal through both point (CSO and stormwater outfalls) and non‐point (surface runoff) sources. Although these bacteria are typically not directly pathogenic for humans, they may co‐occur with pathogens and thereby are used as a water quality indicator.

Fecal coliform bacteria were sampled monthly at 1 m at the King County long‐term monitoring sites. In addition to characterizing current conditions, concentrations were analyzed for long‐term trends and the last 10 years of data were compared to Ecology’s Surface Water Criteria (WAC‐173‐201A‐200) to define current water quality impairments.

3.3.1 Current Conditions From 2004 through 2013, the concentrations of fecal coliform bacteria ranged from no detection to detection of 1,700 colony‐forming units per 100 mL (CFU/100 mL) (Table 3‐2). The median values are much lower than the mean values, indicating that the data may not be normal. The maximum value (Fremont–NW Lake Union site) is distinct from values at the other sites for the same date (Sept. 6, 2006), which were all less than 20 CFU/100 mL. Because there was no rainfall in the three days prior to sampling, this high value may be due to direct deposition or sampling error.

The concentrations at the five monitoring sites were significantly different (Kruskal‐Wallis p‐value < 0.0001) (Figure 3‐2). Bacteria concentrations tend to increase moving downstream from the Locks–Salmon Bay to the Montlake Cut sites. The median value for the NE Lake Union‐Portage Bay site, however, is greater than for Dexter–SW Lake Union, but this may be due, in part, to the fact that the NE Lake Union–Portage Bay site was sampled only through 2008.

Table 3-2. Concentrations (CFU/100 mL) of fecal coliform bacteria at 1-m depth in Lake Union/Ship Canal (2004–2013). Site FOD Min. Max. Median Mean Locks-Salmon Bay 166/166 2 620 25 57.0 Fremont–NW Lake 67/67 2 1,700 17 60.5 Union Dexter–SW Lake Union 161/168 0 670 8 26.4 NE Lake Union– 80/80 1 200 12 22.1 Portage Bay Montlake Cut 181/181 1 39 4 5.6 FOD = frequency of detection.

King County 3–5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-2. Fecal coliform bacteria concentrations at 1-m depth at sites in Lake Union Ship Canal (2004–2013).

3.3.2 Comparison to Criteria Lake Union is listed as a Category 5 impaired waterbody on Ecology’s 303(d) list of impaired waters because of violations of the extraordinary water quality standard for concentrations of fecal coliform bacteria. Lake Union/Ship Canal is categorized as an Extraordinary Primary Contact Recreation area. Fecal coliform organism levels for this classification must not exceed a geometric mean value of 50 colonies/100 mL, with no more than 10 percent of all samples (or any single sample when less than 10 sample points exist) obtained for calculating the geometric mean value exceeding 100 colonies/100 mL.

The geometric mean for fecal coliform was calculated using a 12‐month moving window. Figure 3‐3 presents a graphical comparison of observed and geometric mean values to the respective peak and mean criteria. Highlights are as follows:  At the Montlake Cut site, no exceedances of criteria were observed. This is likely because of the high flow and low residence time of water at the surface of the Montlake Cut especially during wet‐weather events. Any CSO or stormwater discharges into Union Bay and Montlake Cut are diluted and do not concentrate anywhere in the Montlake Cut. During wet weather, the dominant circulation pattern would likely be water flowing from Union Bay into Portage Bay, where some accumulation along the shoreline may occur.  Despite the many outfalls in Portage Bay, values at the NE Lake Union–Portage Bay site exceeded 100 CFU/100 mL in only 3 of the 80 samples. The relatively low

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number of exceedances at this site and the large volume discharged from the University CSO suggest that much of the stormwater and CSO outflow into Portage Bay is partially entrained in the southern portion of Portage Bay, quickly pushed into the northeastern arm of Lake Union past the NE Lake Union–Portage Bay site, and substantially diluted by inflow from Lake Washington.  Concentrations above peak standards occurred more frequently at the Fremont–NW Lake Union and Dexter–SW Lake Union sites. In addition to being influenced by nearby stormwater outfalls, concentrations at the Fremont site may be influenced by overflows from the nearby uncontrolled Seattle CSO (147). Concentrations at the Dexter site are potentially influenced by the county Dexter Ave CSO, Seattle CSOs, stormwater outfalls, and runoff from nearby docks.  Violation of standards was most common at the Locks–Salmon Bay site. Many pathways of fecal coliform bacteria enter Salmon Bay, including Seattle CSOs (150/151 and 152), county Ballard and 11th Ave NW CSOs, runoff from docks and shoreline, and multiple stormwater outfalls. The dominant circulation pattern in the system pushes the bacteria westward toward the Locks site. Contribution of marine‐ borne fecal coliform from operation of the Locks is not the likely cause of higher fecal coliform levels at the Locks site because of the low survival time of fecal coliform in marine waters and because marine‐sourced water is highly diluted prior to reaching Salmon Bay’s surface (Tomlinson et al., 1977).

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2004 2005 2006 2007 2008 JFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASOND Locks XXX X X XX XX Fremont XXXX X Dexter XX XX NE Lake Union XXX Montlake 2009 2010 2011 2012 2013 JFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASOND Locks XX XXX X Fremont ------Dexter XXX NE Lake Union ------Montlake

-- = Samples Not Collected = Fail Peak Standard = Pass Both Standards = Fail Geometric Mean Standard X = Sample with > 100 Colonies / 100 ml = Fail Geometric Mean Standard and Peak Standard Figure 3-3. Water quality criteria violations of fecal coliform bacteria in Lake Union/Ship Canal. An X denotes a high colony count but does not signify a violation.

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3.3.3 Long-Term Trends Long‐term trend analysis of fecal coliform bacteria concentrations found significant downward trends at all sites for seasonally weighted data (Table 3‐3). The Locks–Salmon Bay site had the greatest decrease in fecal coliform bacteria during the sample period. Historically, this site has shown the greatest variation and spikes in annual geometric means, but since 2008, the means have remained consistently low (Figure 3‐4).

Trend results for individual seasons are presented in Appendix C. All sites except Fremont– NW Lake Union and Montlake Cut show significant trends for all four seasons. The Montlake Cut site had a significant downward trend for the fall and winter seasons when wet‐weather events are common.

Fecal coliform concentrations were found to be highly correlated with cumulative three‐ day rainfall. Appendix C provides further discussion on the correlations between bacteria concentrations and rainfall, suspended solids, and phytoplankton biovolume.

Table 3-3. Seasonal Mann-Kendall trends for fecal coliform bacteria concentrations in Lake Union/Ship Canal. Magnitude Years Site Direction Significance p-value (CFU/100 Evaluated mL/yr) Locks-Salmon Bay 1976–2013 ⇩ *** <0.0001 –1.60 Fremont–NW Lake 1992–2008 ⇩ ** 0.0497 –1.00 Union Dexter–SW Lake 1984–2013 ⇩ *** <0.0001 –1.02 Union NE Lake Union– 1992–2008 ⇩ *** <0.0001 –1.57 Portage Bay Montlake Cut 1984–2013 ⇩ *** <0.0001 –0.62 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

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Figure 3-4. Annual fecal coliform bacteria geomeans in Lake Union/Ship Canal (1976–2013).

3.4 Physical Parameters

Physical water quality data includes temperature, salinity, conductivity, DO, turbidity, TSS, pH, and alkalinity. With the exception of salinity, these parameters are measured as part of King County’s routine monitoring program in Lake Union/Ship Canal. Conductivity, however, may be used to calculate salinity.

3.4.1 Temperature The temperature of water in lakes is an important driving factor in metabolic and chemical activity and for thermal stratification. Additionally, higher water temperatures can adversely impact certain species. Water temperature is largely influenced by the absorption of solar radiation, although thermal pollution from surface runoff and CSOs can potentially affect small localized areas in the lake system at a small timescale. The temperature of lakes in the Pacific Northwest exhibits a seasonal pattern with well‐mixed water in the winter and early spring and thermal stratification beginning in the spring and lasting through the fall (Wetzel, 2001).

Lake Union is a warm monomictic lake that stratifies in the warm summer months and mixes isothermally in the winter (Metro, 1993; City of Seattle, 1994). Stratification occurs weakly and rarely in Salmon Bay and Portage Bay because of shallow depths and perturbation by incoming flow from upstream and by operation of the Locks.

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Current Conditions Figure 3‐5 displays the temperature profile in Lake Union over the course of the year using median 2009–2013 values from the Dexter–SW Lake Union site:  The water column is isothermal until late April or early May, when a very weak thermocline begins forming at an approximately 10‐m depth as the water below remains cooler than that above.  By mid‐June, a moderate, stable thermocline has developed, where the surface and bottom temperatures differentiate by approximately 5°C (see Appendix C).  Throughout July and August, Lake Union is thermally stratified at its greatest strength with a temperature differential of 5 to 10°C. Partial turnover occurs rarely in June and July.  In September or October, turnover occurs and the lake becomes isothermal once more. The timing of turnover depends on wind and rainfall and can also be influenced by the presence of a saltwater layer. Because of the density‐driven isolation of the saltwater layer, bottom temperatures may be greater than surface temperatures in the winter and as late as March. From 2004 through 2013, a measurable saltwater bolus occurred at depth at the Dexter site in 4 of the 10 years.

Figure 3-5. Time-depth isopleths of median monthly temperature at the Dexter-SW Lake Union site (2009–2013).

Using rLakeAnalyzer (Winslow et al., 2014), the mean depth of the thermocline during July and August was found to be 10.3 ± 0.2 m (n = 40). Thus, the typical volume in Lake Union of the epilimnion is 18.2*106 m3 and the volume of the hypolimnion is 5.2*106 m3.

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While Salmon Bay has a maximum depth greater than 10 m, thermal stratification of Salmon Bay is not likely to occur. Its small size, constant perturbation by operation of the Locks, and inflow from the Fremont Cut cause a short residence time and prevent the establishment of a thermocline. This phenomenon cannot be verified from data collected at the Locks–Salmon Bay site because its maximum temperature sampling depth is 8 m. At the USACE Ballard Bridge site, sampled at 3.4 m, 6.4 m, and 9.8 m, temperature variations between 6.4 m and 9.8 m occur during periods of saltwater intrusion do not last long.

Spatial temperature variations between the Locks–Salmon Bay, Dexter–SW Lake Union, and Montlake Cut sites were not statistically significant (Kruskal‐Wallis p‐value = 0.8901) (Figure 3‐6). Spatial temperature variations within individual seasons were not detected (p‐values > 0.85).

Figure 3-6. Surface temperature (0–5 m) in Lake Union/Ship Canal (2009–2013).

Impacts on Migrating Salmonids Water temperatures greater than 21°C have been found to act as a barrier to migrating salmon (Ecology, 2002). Warm daily temperature (15.5–20°C) are assoicated with pre‐ spawning mortalitiy, thermal stress, and reduced reproductive success. A literature review by Ecology concluded the following:  Adult migrants are likely to be detrimentally impacted at a 7‐DADMax above 17– 19°C.  Barriers to migration and direct mortality should be expected when 7DADMax temperatures exceed 21.5–22°C.  Lethality should be expected to begin at one‐day maximum temperatures of 22.5– 23°C (Ecology, 2002).

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Tempeatures in Lake Union/Ship Canal were compared to 17°C as an indication of thermal stress and to 21.5°C as an indication of a migratory barrier and direct mortality. In general, it was found that the high temperatures in Lake Union/Ship Canal, especially in shallow Salmon Bay, Fremont Cut, Portage Bay, and Montlake Cut, threaten the success of migrating salmonids and may cause mortality or act as a thermal barrier, inhibiting movement upstream. The following paragraphs provide more detail.

To capture a wide range of variabilty, 10 years of data were analyzed. USACE continuous data from 2004 through 2013 were used to determine the 7‐DADMax for the five USACE sites. At all USACE sites with sampling depths between 0 m and 10 m, the temperature was greater than the thermal stress threshold for almost the whole Ecology‐defined core summer salmonid habitat (Figure 3‐7). Exceedances were far less common below 10 m at the USACE Fremont Bridge and Gas Works sites. Exceedances, however, consistently occurred at 10.7 m at the University Bridge site. These findings can be attributed to the stratification that occurs in the Lake Union basin but not in the narrow strip between Lake Union and Portage Bay. Temperature at depth in the Lake Union basin occasionally exceeded standards in late August and September at Fremont Bridge, Gas Works, or both.

In Salmon Bay, at or near the USACE Large Locks, Ballard Bridge, and University Bridge sites, summer temperatures in the entire water column were occasionally greater than the mortality and migratory barrier threshold. In the thermally stratified and unmixed Lake Union stations at Fremont Bridge and Gas Works, near‐surface temperatures sometimes exceeded the mortality threshold; temperatures in the hypolimnion did not exceed the threshold.

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Figure 3-7. 7-DADMax at USACE sites in Lake Union/Ship Canal (2004–2013). Ecology-defined core summer salmonid habitat is highlighted in yellow. Thermal stress threshold is shown as pink line, and direct mortality and thermal barrier threshold is shown as red line (source: USACE unpublished data).

Long-Term Trends Surface temperatures in the Pacific Ocean shift between warm and cool phases on a decadal scale; this occurrence is known as the Pacific Decadal Oscillation (PDO) and is detected as positive or negative monthly temperature anomalies (Mantua et al., 1997). Arhonditsis et al. (2004) found a warming trend in Lake Washington with a mean increase of 0.026°C per year that was most strongly associated with air temperatures and the PDO.

Seasonal and annual effects of the PDO were included as a covariate in the trend analysis. Monthly values for the PDO index were obtained from the Joint Institute for the Study of the Atmosphere and Oceans at the University of Washington (http://tao.atmos.washington.edu/datapsets/).

The multivariate regression equation used was as follows:

sin 2 cos 2

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Where: is the monthly average temperature is the intercept are the regression coefficients

The significance of and magnitude of the statistic was used to determine the trend. The sine and cosine functions allow for the seasonality of air temperature and solar angle (Helsel and Hirsh, 2002).

Annualized temperature trends for the King County monitoring sites are presented in Table 3‐4. Statistically significant temperature increases were detected at the Locks–Salmon Bay, the surface of Dexter–SW Lake Union, and Montlake Cut sites.

Table 3-4. Temperature trends in Lake Union/Ship Canal determined through multivariate regression. Years Magnitude Site Depth Direction Significance p-value Evaluated (°C/year) Locks-Salmon All 1986–2013 ⇧ *** 0.0006 0.044 Bay Fremont–NW All 1986–2008 -- n.s. 0.8318 0.005 Lake Union Dexter–SW 0–5 m 1985–2013 ⇧ ** 0.0330 0.029 Lake Union 10–15 m 1985–2013 -- n.s. 0.4377 –0.011 NE Lake Union– All 1986–2008 -- n.s. 0.8420 0.045 Portage Bay Montlake Cut All 1986–2013 ⇧ * 0.0761 0.023 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

Significant increasing trends were identified for the Locks–Salmon Bay site during the summer, winter, and spring; for the Montlake Cut site during the summer and winter; for the hypolimnion at the Dexter–SW Lake Union site during the winter; and for the epilimnion at the Dexter–SW Lake Union site during the winter and spring. A significant decreasing trend of 0.138 °C per year was detected in the hypolimnion at Dexter–SW Lake Union site during the summer, which is the period of stratification (Figure 3‐8). (See Appendix C for more information on seasonal trends.)

Weitkamp et al. (2000) noted that the duration of the high temperatures (> 20°C) in Lake Union/Ship Canal had increased from an average of 31 days per year in the 1970s to approximately 80 days per year in the late 1990s. From 2009 through 2013, an average of 79.6 days per year had a maximum temperature greater than 20°C, which suggests a lull in warming between the late 1990s and the early 2010s.

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Figure 3-8. Mean summer hypolimnetic temperatures at the Dexter-SW Lake Union site (1985−2013). Regression slope = −0.138°C per year; p < 0.0001.

The cooling trend found in the summer for the hypolimnion at the Dexter–SW Lake Union site may be attributed to a longer period of stratification from earlier warming and with greater strength. Warming of the thermally isolated hypolimnion lags behind warming of the epilimnion. While saltwater intrusion plays a role in hypolimnetic temperatures, there is no evidence that Locks operations or saltwater drain malfunctions have increased or decreased over the past three decades.

For the first 10 years of the evaluation period (1985−1995), surface‐bottom temperature differences at the Dexter–SW Lake Union site were less extreme than differences from the last 10 years (2004−2013 (Table 3‐5). Generally, stratification persisted until October only three times in 1985–1995; whereas, stratification persisted until October nine times in 2004–2013. For July through October, the temperature of the hypolimnion was significantly greater in 1985–1995 than in the 2004–2013, as was the temperature of the epilimnion for the month of October.

Monthly mean lake surface temperatures (≤ 5 m depth) are strongly correlated with local air temperature (Pearson’s correlation coefficient = 0.642, p‐value < 0.0001).6 Summertime hypolimnetic temperatures are negatively correlated with local air temperature (Pearson’s correlation coefficient = −0.2289, p‐value = 0.0330). This supports the hypothesis that more intense thermal stratification is associated with a decrease in hypolimnetic temperatures, although salt water may enter and warm the hypolimnion. The Dexter Ave CSO, whose outlet is at 10.4 m, may also influence summer hypolimnetic temperature. In the summer, the thermocline varies between 8 and 12 m, depending on weather conditions. However, the Dexter Ave CSO is unlikely to discharge in dry summer months.

6 Monthly mean temperature from SeaTac station.

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Table 3-5. Comparison of epilimnion and hypolimnion mean monthly temperatures and p- values from two-sided, two-sample t-test for two periods (1985–1995 and 2004– 2013) at the Dexter–SW Lake Union site. Values in bold indicate differences at a 0.05 level of significance. Epilimnion (0–10.3 m) Hypolimnion (10.3 m to bottom) Month 1985–1995 2004–2013 p-value 1985–1995 2004–2013 p-value January 6.5 7.3 0.0005 6.6 7.1 0.1252 February 6.2 7.0 0.0002 6.3 6.9 0.0874 March 7.7 7.8 0.4483 7.4 7.7 0.3460 April 9.8 9.7 0.5887 9.1 9.0 0.5882 May 13.1 13.3 0.5326 11.2 11.0 0.4086 June 16.4 16.4 0.8987 13.1 13.1 0.9459 July 19.3 19.5 0.7209 15.7 14.1 0.0054 August 20.9 20.7 0.2554 16.7 14.9 < 0.0001 September 19.6 19.5 0.5836 17.4 15.7 < 0.0001 October 16.5 15.6 0.0030 16.4 15.2 0.0224 November 12.0 11.9 0.5758 12.1 12.1 0.9717 December 8.3 8.4 0.6851 8.4 8.4 0.9579

3.4.2 Salinity/Conductivity Salinity is a measure of the dissolved salt content in water; it impacts the chemistry and density of waters and biological processes. Seawater typically has a salinity of 35 parts per thousand (ppt) and fresh water a salinity of 0–0.5 ppt.

Specific conductance (conductivity) is a measure of the capacity of water to conduct an electric current standardized at 25°C, allowing comparison of waters of different temperatures. Temperature and the concentration of major dissolved ions in water determine its conductivity. High conductivity can lead either to decreased toxicity from the complexation of otherwise toxic ions or to increased uptake of these toxic ions (Environment Canada, 2001; Bidwell and Gorrie, 2006; Zalizniak et al., 2006). Additionally, increased conductivity can negatively affect biota via osmotic stress.

Ecology has established a salinity criterion of no higher than 1 ppt at any point or depth along a line that transects the Ship Canal at the University Bridge over Portage Bay (WAC 173–201A–130). During 2004 through 2013, this criterion was never exceeded at any depth at the USACE station near the University Bridge (UBLW).

Conductivity concentrations were used for trend analysis, and salinity concentrations were used for the assessment of current conditions to better illustrate saltwater intrusion. Conductivity values may be converted to salinity via methods outlined by Wooster et al. (1969). The precision of these methods decreases below 2 ppt salinity, but the concentrations can still effectively illustrate salinity differences in the water column.

King County 3–17 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Current Conditions Figure 3‐9 displays the salinity profile over the course of the year using median 2009–2013 values at the King County Dexter‐SW Lake Union site. Salinity reached a median of 0.7 ppt in late summer and early fall at the bottom of Lake Union prior to fall turnover in September or October. Salinity was 1.5 ppt in late summer 2009, less than 0.1 ppt in 2010, 0.5 ppt in 2011, 0.7 ppt in 2012, and 3.3 ppt in 2013. The effects of saltwater intrusion have not been captured at the other four county monitoring sites because of their shallow maximum sampling depths (5, 8, 3, and 8 m); the saltwater wedge would likely be found at 9 m and below. The Locks–Salmon Bay site, however, has relatively high salinity concentrations because of its proximity to the Locks.

Figure 3-9. Time-depth isopleths of median monthly salinity values at the Dexter–SW Lake Union site (2009–2013).

The USACE continuous monitoring sites provide a better picture of the spatial distribution of salt water in Lake Union (Appendix C). Salinity at the Large Locks and Ballard Bridge sites depends on the rate of operation of the Locks and the efficiency of the saltwater drain; from late spring to mid‐fall, salinity concentrations at the greatest sampling depths at the Large Locks and Ballard Bridge sites typically range from 1 ppt to 6 ppt and 0.1 ppt to 1.0 ppt, respectively. The saltwater wedge does not reach the Fremont Bridge and Gas Works sites until May or June. Once the wedge reaches the Fremont Bridge, the Lake Union basin begins to fill. This filling is visible at the Gas Works site and the County’s Dexter–SW Lake Union site (see Figure 3‐9). Evidence of the saltwater wedge does not appear at the University Bridge site until July or August, and its presence is not lasting. It appears for one day to one month at concentrations less than 0.5 ppt.

King County 3–18 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Long-Term Trends Because of the incongruence between conductance measurements taken in the field using the Hydrolab® and those in the laboratory using the SM2510B method, trend analysis for conductivity was limited to data collected using the Hydrolab® (1992 and after). Volume‐ weighted conductivity values were used to evaluate trends for Lake Union/Ship Canal. No substantial trends in conductivity were observed, although a significant decrease at the Locks–Salmon Bay site was found (Table 3‐6). These findings support the idea that Locks operations or malfunctions have not changed over the study period and that saltwater intrusion is not the dominant cause for the observed increase in the strength and length of thermal stratification in Lake Union/Ship Canal.

Table 3-6. Seasonal Mann-Kendall trends for volume-weighted conductivity in Lake Union/Ship Canal. Site Years Direction Significance p-value Magnitude Evaluated (µS/cm/yr) Locks-Salmon Bay 1997–2013 ⇩ ** 0.0325 –1.64 Fremont–NW Lake 1992–2008 ‐‐ n.s. 0.3672 0.25 Union Dexter–SW Lake 1992–2013 ‐‐ n.s. 0.8615 0.06 Union NE Lake Union– 1992–2008 ‐‐ n.s. 0.5227 0.10 Portage Bay Montlake Cut 1992–2013 ‐‐ n.s. 0.7539 0.03 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

3.4.3 Dissolved Oxygen DO is the measure of molecular oxygen gas dissolved in water. DO is necessary for the respiration and metabolism of aerobic organisms; its availability also determines the direction of reduction‐oxidation reactions in the water and bottom sediments. Oxygen enters the lake system through diffusion from the atmosphere and as a byproduct of photosynthesis completed by phytoplankton and aquatic macrophytes. Concentrations depend on temperature, atmospheric pressure, primary productivity, aerobic respiration, and chemical oxygen demand.

Current Conditions Figure 3‐10 displays DO concentrations in Lake Union over the course of the year using median 2009–2013 values from the Dexter–SW Lake Union site. DO peaks at approximately 12 mg/L in the spring during the diatom bloom. With the onset of stratification, hypolimnetic DO declines to below the MDL (0.5 mg/L) in late June or early July, and the hypolimnion remains anoxic through the course of stratification. The anoxic region is closely delimited by the region of salinity and the depth of the thermal gradient (see Figures 3‐5 and 3‐8). The advent of anoxia occurs prior to the saltwater intrusion. It is caused by consumption of DO through the oxidation of organic material and the thermal stratification that prevents vertical mixing.

King County 3–19 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-10. Time-depth isopleths of median monthly dissolved oxygen concentrations at the Dexter –SW Lake Union site (2009–2013).

Figure 3‐11 shows monthly 2004–2013 DO concentrations for the Locks–Salmon Bay and Dexter‐SW Lake Union sites. In the late summer when rising temperatures decrease the solubility of oxygen and heightened surface respiration occurs, DO concentrations in the epilimnion decline. With fall turnover, DO becomes equivalent throughout the water column and eventually reaches equilibrium with the atmosphere in October or November. The minimum December concentrations shown for the Dexter‐SW Lake Union site in Figure 3‐11(b) illustrate extended stratification and anoxia from the increased saltwater intrusion from USACE experiments at the Locks in 2013. The salt water resisted active mixing with the upper water column.

Because all the sampling depths at the Locks–Salmon Bay, Fremont–NW Lake Union, NE Lake Union–Portage Bay, and Montlake Cut sites are in the epilimnion, DO data do not vary greatly with depth; the concentrations remain equivalent throughout the water column above the thermocline at 10 m. Below the thermocline, the water becomes anoxic. Consistent anoxia is present at the sediment/water interface of roughly 1.5 * 106 m2 of the lake bottom during stratification.

King County 3–20 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-11. Dissolved oxygen concentrations at the (a) Locks–Salmon Bay and (b) Dexter–SW Lake Union sites (2004–2013). White boxes represent 1-m samples; grey boxes represent 5-m samples (Locks) and 14-m samples (Dexter).

DO concentrations at the surface are slightly lower at the Locks–Salmon Bay site than at Dexter–SW Lake Union and Montlake Cut sites (Figure 3‐12) (Kruskal‐Wallis p‐value = 0.0051). The difference is most apparent in the summer when the mean Locks DO concentration is 7.98 mg/L and the mean Dexter and Montlake concentrations are 8.34 mg/L and 8.55 mg/L, respectively. This may be due to elevated levels of aerobic respiration and chemical oxidation in Salmon Bay, associated with inputs of oxygen‐depleting

King County 3–21 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

substances such as organic detritus and oxidizable metals from Fisherman’s Terminal, nearby CSO and stormwater outfalls, and upstream sources.

Figure 3-12. Dissolved oxygen concentrations in the epilimnion in Lake Union/Ship Canal (2009–2013).

Impacts on Migrating Salmonids Low DO concentrations act as a barrier to and threaten salmonids migrating through Lake Union/Ship Canal. DO levels greater than 6 mg/L are optimal for salmonids, levels less than 4.25 mg/L stress salmonids, and levels less than 2 mg/L are lethal to salmonids (Davis, 1975; City of Seattle and USACE, 2008).

Figure 3‐13 shows the daily DO minimum for stratum in Lake Union/Ship Canal from 2004 through 2013. Surface DO concentrations remain above 6 mg/L throughout the year. In Lake Union at the Dexter–SW Lake Union and Fremont–NW Lake Union sites, DO concentrations below 5 m will typically dip below 6 mg/L and in some cases below the 4.25‐mg/L critical threshold. Hypoxia/anoxia occurs every summer in the hypolimnion (> 10 m), preventing it from serving as a thermal refuge for migrating salmonids. The DO barrier forces salmonids in Lake Union/Ship Canal to experience thermal stress in the upper water column.

King County 3–22 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-13. Minimum dissolved oxygen (DO) concentrationns at King County monitoring sites in Lake Union/Ship Canal (2004–2013). Ecology-defined core summer salmonid habitat is highlighted in yellow. Optimal minimum DO level is shown as green line, critical DO level is shown as pink line, and lethal DO level is shown as red line.

King County 3–23 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Long-Term Trends Because of the incongruence between DO measurements taken in the field using the Hydrolab® and those in the laboratory using the Winkler method, trend analysis for DO was limited to data collected using the Hydrolab® (1993 and after). DO concentrations were volume‐weighted prior to analysis.

Table 3‐7 presents the results for the annualized trend analysis. The analysis found that DO has significantly decreased at the NE Lake Union–Portage Bay site during the summer and on an annual basis.

Table 3-7. Seasonal Mann-Kendall trends for volume-weighted dissolved oxygen concentrations in Lake Union/Ship Canal. Years Magnitude Site Direction Significance p-value Evaluated (ppm/yr) Locks-Salmon 1997–2013 n.s. 0.6654 –0.005 Bay ‐‐ Fremont–NW 1993–2008 n.s. 0.9191 0.002 Lake Union ‐‐ Dexter–SW Lake 1993–2013 n.s. 0.2906 0.015 Union ‐‐ NE Lake Union– 1993–2008 ⇩ *** 0.0057 –0.031 Portage Bay Montlake Cut 1997–2013 ‐‐ n.s. 0.4627 –0.015 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

Appendix C presents information on seasonal DO trends. The Locks–Salmon Bay site had slightly significant decreasing DO values during the spring. Although all sites show a decreasing trend during the summer, the reason for the strong trend at the NE Lake Union– Portage Bay site is not apparent. Decreases in DO may be linked to the warming of waters, but a significant increase in temperature at this site was not detected. (The Montlake Cut site had a slightly significant negative trend during the summer.)

3.4.4 Turbidity/Total Suspended Solids/Secchi Transparency Turbidity, TSS, and Secchi transparency are influenced by phytoplankton biomass, resuspended sediment, and inputs of particles from stormwater outfalls, CSO outfalls, and surface runoff. These three metrics are described below:  Turbidity is a measure of the cloudiness of water and is quantified by determining the scattering of light by particles in a sample of water. Individual particles in turbid water are often too small to be visible to the naked eye and may not be captured by filtration for analysis of TSS.  The measure of TSS is the total mass of particles greater than 1.5 microns in diameter in a sample of water, generally measured by dry weight (dw) after filtration.

King County 3–24 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

 Secchi transparency is the maximum depth of visibility of a Secchi disk, a black and white circle of a specific diameter lowered to disappearance and the vertical distance from the surface recorded.

Current Conditions From 2009 through 2013, the mean Secchi transparency depth in Lake Union/Ship Canal was 3.8 m and the median depth was 3.7 m. The Montlake Cut site had greater transparency than the Locks–Salmon Bay and Dexter–SW Lake Union sites (Table 3‐8 and Figure 3‐14). Transparency was typically greatest in December and January. The lowest visibility generally occurred in May; however, transparency reached 6 m in May 2010.

Turbidity remains below 3 NTU and TSS remains below 5 mg/L in the epilimnion of Lake Union/Ship Canal throughout the year at all stations (Table 3‐8).7 An increase in turbidity at the surface is detectable in spring, coinciding with the spring diatom bloom. Both TSS and turbidity in the hypolimnion increase to a maximum in mid‐ to late summer during stratification as detrital biomass falls from the epilimnion and, potentially, as bottom sediments are resuspended. At the surface during this period, particle densities are much lower and turbidity reaches its annual minimum.

Table 3-8. Secchi transparency and total suspended solids (2009–2013) and turbidity (2004– 2008) in Lake Union/Ship Canal. Parameter Site Depth FOD Min. Max. Median Mean Locks–Salmon Bay NA 101/101 1.5 5.5 3.5 3.5 Secchi Dexter–SW Lake Transparency NA 101/101 1.8 6.7 3.6 3.8 Union (m) Montlake Cut NA 100/100 2.1 7.0 4.0 4.1 Locks–Salmon Bay Epilimnion 179/179 0.6 5.0 1.3 1.4

Dexter–SW Lake Epilimnion 246/246 0.6 3.5 1.1 1.3 TSS (mg/L) Union Hypolimnion 96/101 < 0.5 46.0 1.7 5.0 Locks–Salmon Bay Epilimnion 182/182 0.5 3.0 1.2 1.2 Locks–Salmon Bay Epilimnion 119/125 < 0.5 2.6 0.95 1.1

Turbidity Dexter–SW Lake Epilimnion 165/187 < 0.5 2.0 0.86 0.89 (NTU) Union Hypolimnion 58/61 < 0.5 21.8 1.7 4.8 Locks–Salmon Bay Epilimnion 124/140 < 0.5 1.8 0.76 0.84

FOD = frequency of detection; NTU= Nephelometric Turbidity Unit.

7 Turbidity monitoring was discontinued in 2008; NTU = Nephelometric Turbidity Unit.

King County 3–25 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-14. Secchi transparency in Lake Union/Ship Canal (2009–2013).

Turbidity and TSS were statistically greater near the Locks–Salmon Bay site than at the Dexter–SW Lake Union and Montlake Cut sites (Kruskal‐Wallis p‐values = < 0.0001 and 0.0459, respectively) (Figure 3‐15). The Locks–Salmon Bay site had greater turbidity values during individual seasons than the other two sites. TSS values showed spatial variability only in the fall, with the TSS values at the Locks–Salmon Bay and Dexter–SW Lake Union sites were statistically greater than values at the Montlake Cut site.

a b

Figure 3-15. Epilimnion (a) turbidity values (2004–2008) and (b) TSS values (2009–2013) in Lake Union/Ship Canal.

King County 3–26 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Long-Term Trends Because of method changes and inconsistent monitoring, trend analysis could not be completed for turbidity and TSS. Secchi transparency was consistently measured and trends were calculated.

Overall, transparency in Lake Union/Ship Canal has either increased or remained constant over the past 30 years (Table 3‐9). Turbidity, which has a negative relationship with transparency, has therefore likely decreased. These trends may be partially explained by improved CSO and stormwater infrastructure, causing a decrease in nutrient and fine sediment loading. Trends for TSS cannot be confidently extrapolated from Secchi transparency data.

Secchi transparency significantly increased at the Fremont‐NW Lake Union and NE Lake Union–Portage Bay sites on an annual basis (Table 3‐9). Transparency increased at the NE Lake Union–Portage Bay site during summer and winter and at the Fremont–NW Lake Union site during summer only. Transparency at the Dexter–SW Lake Union and Montlake Cut sites increased significantly during winter only.

Table 3-9. Seasonal Mann-Kendall trends for Secchi transparency in Lake Union/Ship Canal. Years Magnitude Site Direction Significance p-value Evaluated (m/yr) Locks-Salmon Bay 1997–2013 ‐‐ n.s. 0.1353 0.019 Fremont–NW Lake 1986–2008 * 0.0512 0.038 Union ⇧ Dexter–SW Lake 1985–2013 n.s. 0.4718 0.002 Union ‐‐ NE Lake Union– 1986–2008 *** 0.0049 0.057 Portage Bay ⇧ Montlake Cut 1997–2013 ‐‐ n.s. 0.1614 0.025 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

3.4.5 pH and Alkalinity

pH is the negative log10‐ transformation of the activity of hydrogen ions in solution. pH values less than 7 are considered acidic; values greater than 7 are considered alkaline or basic. pH influences the chemical state of metals and other constituents. Some organisms may have a narrow range of optimal pH and can be negatively impacted at high and low pH values.

Total alkalinity, also called acid neutralizing capacity (ANC), is a measure the ability of the body of water to resist a decrease in pH by the addition of an acid (buffering capacity). Alkalinity is reported as mg CaCO3/L because of the importance of bicarbonate concentrations in freshwater systems.

King County 3–27 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

pH was sampled monthly at the Locks–Salmon Bay, Dexter–SW Lake Union, and Montlake Cut sites from 2009 through 2013.

Alkalinity was sampled quarterly in January, April, July, and October at the Locks–Salmon Bay, Fremont–NW Lake Union, NE Lake Union–Portage Bay, and Montlake Cut sites from 1992 or 1997 through 2008 and at the Dexter–SW Lake Union site from 1985 through 2008. The Dexter site was sampled for alkalinity monthly from 2009 through 2013.

Current Conditions Alkalinity values from 2003 through 2008 are indistinguishable between all Lake Union/Ship Canal sites, with a mean and median value of 39 mg CaCO3/L.

Generally, Lake Union/Ship Canal is slightly basic (7 < pH < 8). Moving upstream from the Locks, epilimnetic pH increases (Figure 3‐16). The pH values at the Locks–Salmon Bay, Dexter–SW Lake Union, and Montlake Cut sites are significantly distinguishable in spring, summer, and fall (Kruskal‐Wallis p‐value < 0.0001). During winter, the sites are not distinguishable (p‐value = 0.1108).

Figure 3-16. Epilimnion pH values in Lake Union/Ship Canal (2009–2013).

Lake Union/Ship Canal shows a seasonal regularity, characterized by pH peaks in spring during the diatom bloom (Appendix C). As phytoplankton photosynthesize, they consume dissolved CO2 (H2CO3) and decrease acid in the lake. This period of peak pH persists until early summer when respiration begins to outpace photosynthesis. With the onset of stratification, the pH in the hypolimnion decreases as heterotrophic organisms consume DO and detritus and increase the levels of bicarbonate (HCO3‐) and CO2/H2CO3. When

King County 3–28 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

oxygen levels drop to concentrations below levels that support aerobic decomposition, anaerobic bacteria in the hypolimnion chemically reduce iron, manganese, sulfate, and nitrate, contributing ANC and preventing decreases in pH (Kling et al., 1991). Fall turnover equalizes pH and alkalinity throughout the water column.

Comparison to Criteria Ecology has established an aquatic life pH criterion for Lake Union/Ship Canal as core summer salmonid habitat. Summer is defined as June 15 through September 15 (WAC 173‐ 201A‐200). During the summer, the pH must be within the range of 6.5 to 8.5, with a human‐caused variation to the range of less than 0.2 unit.

From 2004 through 2013, this criterion was exceeded once near the Locks–Salmon Bay site, three times at the Dexter–SW Lake Union site, and twice at the Montlake Cut site (Figure 3‐17). There were no exceedances at the Fremont–NW Lake Union and NE Lake Union–Portage Bay sites during the same period.

Peak pH values from the diatom bloom in spring usually drop below 8.5 before June 15. In instances of late blooms, the 8.5 criterion may be exceeded. The lower limit of 6.5 was not met at depth in samples from the hypolimnion at the Dexter–SW Lake Union site and at both the 1‐m and 5‐m depths at the Locks–Salmon Bay site on one sampling trip during the past 10 years.

The values that exceed the water quality criterion are within the normal pH range for mesotrophic lakes. While little historical data exist for evaluation of water quality before development, the loading of excess nutrients from human activities is likely contributing to the spring pulse of phytoplankton growth, the development of anoxic layers, and the high pH in the hypolimnion during the summer; the loading of oxygen‐depleting substances and the intrusion of salt water also contribute to the summertime anoxia.

King County 3–29 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-17. pH values in Lake Union/Ship Canal compared to water quality criterion (2004– 2013). Red line represents surface pH; black line represents the bottom sample. Low and high ends of criterion range (6.5 and 8.5) are shown as solid lines. Ecology-defined core summer salmonid habitat is hightlighted in yellow.

Long-Term Trends Because of incongruent pH analysis methods, trend analyses were performed only for data collected since 1992. The data were volume‐weighted using hydrogen ion activities transformed from pH values (10‐pH) and were back‐transformed to pH for performing the Mann‐Kendall test for trends using cumulative three‐day rainfall as a covariate.

Significant increasing pH trends were found on an annual basis at the Dexter–SW Lake Union, NE Lake Union–Portage Bay, and Montlake Cut sites (Table 3‐10). These increases were seen during the fall and winter (Appendix C). The steepest seasonal trend was observed at Montlake Cut in the winter, which increased at a rate of 0.026 unit per year. No trends were found in the fall at this site or at the Locks–Salmon Bay site, nor were trends seen in the winter at the Fremont–NW Lake Union site.

King County 3–30 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table 3-10. Seasonal Mann-Kendall trends in Lake Union/Ship Canal for volume-weighted pH based on hydrogen ion activity. Years Magnitude Site Direction Significance p-value Evaluated (units/yr) Locks-Salmon Bay 1992–2013 ‐‐ n.s. 0.6685 0.002 Fremont–NW Lake Union 1992–2008 ‐‐ n.s. 0.2128 0.011 Dexter–SW Lake Union 1992–2013 ⇧ * 0.0899 0.007 NE Lake Union–Portage Bay 1992–2008 ⇧ ** 0.0496 0.012 Montlake Cut 1992–2013 ⇧ ** 0.0291 0.010 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

Alkalinity increased signifcantly over time on an annual basis at all sites and during all seasons, except in the fall at the Fremont–NW Lake Union and Dexter–SW Lake Union sites (Table 3‐11). Hypolimnetic alkalinity at Dexter increased during the fall but not during the summer, which supports the notion that stratification and the summer hypolimnion may be persisting for longer periods. The greatest rate of increase was seen near the Locks– Salmon Bay site in the winter, at a rate of 0.55 mg CaCO3/L per year.

Table 3-11. Seasonal Mann-Kendall trends for volume-weighted alkalinity in Lake Union/Ship Canal. Years p- Magnitude Site Direction Significance Evaluated value (mg CaCO3/L/yr) Locks-Salmon Bay 1997–2008 ⇧ *** 0.0008 0.547 Fremont–NW Lake Union 1992–2008 ⇧ ** 0.0468 0.191 Dexter–SW Lake Union 1985–2013 ⇧ ** 0.0113 0.129 NE Lake Union–Portage 1992–2008 ⇧ ** 0.0192 0.215 Bay Montlake Cut 1997–2008 ⇧ *** 0.0010 0.509 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

The magnitude of the trends appears to depend on the years investigated. Because the Dexter−SW Lake Union site was sampled for the longest period, it can provide insight into interdecadal alkalinity trends (Appendix C). Between 1985 and 1995, the site experienced a substantial increase in alkalinity; levels returned to 1985 levels in 1995. From the late 1990s to the late 2000s, another increasing trend is visible.

An increasing alkalinity trend has been observed in Lake Washington, attributed to pertubation and erosion of soils from watershed development (Edmonson, 1994; King County, 2003a). This increase in alkalinity in Lake Washington coupled with development in the immediate Lake Union/Ship Canal watershed may be the primary causes of the observed trends in Lake Union/Ship Canal and the relatively greater slope found for sites sampled between 1997 and 2008. The lack of significant difference between sites during this time period (Kruskal‐Wallis p‐value = 0.7854) suggests that local inputs of alkalinity are eclipsed by the import from Lake Washington. The amount of land use change in the

King County 3–31 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

greater Lake Washington watershed is substantial enough to conceal any impacts from the Lake Union/Ship Canal drainage area (King County, 2011b).

3.5 Chlorophyll a

Chlorophyll a is a photosynthetic pigment that absorbs light energy; it is essential in the process of photosynthesis by autotrophs such as phytoplankton. The concentration of chlorophyll a provides information on the level of phytoplankton biovolume in a lake.

3.5.1 Laboratory and Field Method Changes From 2006 through 2009, King County took discrete depth grab samples and also recorded chlorophyll a in‐situ with a Hydrolab® that provided contiguous profile data. The values from the laboratory analysis are not comparable to the values from the Hydrolab®. Chlorophyll a concentrations in the lab are acid‐corrected for phaeophytin (degraded chlorophyll a); the fluorescence method used by the Hydrolab® can sometimes record non‐ autotrophic particles. The Hydrolab® data, however, may be used to examine relative chlorophyll a concentrations through the water column.

Sampling methods for chlorophyll a varied over time:  Prior to March 1994, samples were collected at 1‐m depth only.  From March 1994 through 2004, each sample collected from 1‐m depth was composited with a sample collected at Secchi depth.  Beginning in 2004 at the Dexter–SW Lake Union site, sample compositing changed to a vertically integrated sample collected using a weighted length of 1.6‐cm Tygon® tubing lowered vertically through the water column to a 10‐m depth, plugged at the surface and at the submerged end by a check valve, and then retrieved. Although observed differences between the two methods were often statistically significant, it was determined that these differences would not substantially affect the ability to detect long‐term trends in seasonally averaged chlorophyll a concentrations (King County, 2004b).  Also beginning in 2004, chlorophyll a samples were taken discretely at 1‐m depth at the other four county sampling sites. Phytoplankton samples were collected using the same methods as chlorophyll a, with the

same changes in methods over time, and were preserved with Lugol’s solution.

KCEL changed analytical methods for chlorophyll a in July 1996. This method change resulted in a 14 percent increase in concentration because of improved extraction. For this analysis, concentrations reported prior to July 1996 were adjusted by increasing them by a factor of 1.14 for comparison with more recent data.

3.5.2 Current Conditions From 2009 through 2013, the concentrations of chlorophyll a at the surface of Lake Union/Ship Canal ranged from less than 0.48 µg/L to 16 µg/L at the three monitoring sites

King County 3–32 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal that were sampled during this time (Table 3‐12). Concentrations were significantly different (Kruskal‐Wallis p‐value = 0.0004) (Figure 3‐18). Concentrations at the Montlake Cut site were lower than at the Locks–Salmon Bay and Dexter–SW Lake Union sites. This discrepancy occurs in the summer and fall (p‐values ≤ 0.0007); the three sites are not distinguishable in winter and spring (p‐values > 0.49).

Table 3-12. Chlorophyll a concentrations (µg/L) in Lake Union/Ship Canal (2009–2013). Min. Max. Site FOD Min. Max. Median Mean MDL MDL Locks–Salmon Bay 98/98 0.84 15.6 4.7 5.2 0.48 1.3 Dexter–SW Lake 98/98 1.5 13.4 4.7 5.1 0.48 1.3 Union Montlake Cut 96/98 < 0.48 16.0 3.4 4.1 0.48 1.3

FOD = frequency of detection; MDL = method detection limit.

Figure 3-18. Chlorophyll a concentrations in Lake Union/Ship Canal (2009–2013).

Chlorophyll a concentrations peak in the spring, coinciding with the diatom bloom. As the biologically available nutrients become limited, the surface water temperature increases, decreased epilimnetic turbulence leads to the settling of non‐motile phytoplankton, and chlorophyll a concentrations decrease greatly at the surface but remain at 4‐ to 7‐m depths. While hypolimnetic waters are high in nutrients, low light and cool temperatures prevent net positive productivity at depth.

During fall turnover, an autumn bloom may occur at the Locks‐Salmon Bay and Dexter‐SW Lake Union sites as nutrients from the hypolimnion mix upward into the euphotic zone. This bloom continues until cool water temperatures and decreased light limit

King County 3–33 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal phytoplankton growth. Additionally, increased flow velocity may prevent phytoplankton bloom accumulation (Dickman, 1969; Tomlinson et al., 1977). The fall bloom is generally not as extensive at the Montlake Cut site as at the other two sites, possibly because of the greater velocity at this site (Figure 3‐19).

Locks–Salmon Bay

Dexter–SW Lake Union

Montlake Cut

Figure 3-19. Monthly chlorophyll a concentrations in Lake Union/Ship Canal (2009–2013).

King County 3–34 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

3.5.3 Long-Term Trends Long‐term trends in chlorophyll a were evaluated for the whole sampling period (mid‐ 1980s through 2013). They were also evaluated for 1997 through 2013 (or the most recent sample) because sampling began in 1997 at two sites (Locks‐Salmon Bay and Montlake Cut) and because of an apparent shift in the chlorophyll a trend direction in the late 1990s (Appendix C).

Trends at specific sites are as follows:  On an annual basis, a slightly significant positive trend was found at the Dexter–SW Lake Union site in 1985–2013 (0.029 ppb/year) (Table 3‐13). From 1997 forward, significant decreasing trends were found at all sites except Montlake Cut at rates between 0.06 and 0.11 ppb per year. These trends were seen in spring and summer only.  On a seasonal basis (Appendix C), significant increases since the 1980s at Fremont– NW Lake Union were found in fall and at Dexter–SW Lake Union in summer. However, in 1997−2013, a decreasing trend was found in spring at Dexter‐SW Lake Union and in summer at Fremont‐NW Lake Union.  Significant decreases at the Locks–Salmon Bay site were found in 1997−2013 in spring and summer at rates of 0.3 ppb and 0.2 ppb per year, respectively. Summer variability has increased since 1997 relative to pre‐1997 variability. The causes for the shifting trend in chlorophyll a concentrations are unknown.

Table 3-13. Seasonal Mann-Kendall trends for chlorophyll a concentrations in Lake Union/Ship Canal. Years Magnitude Site Direction Significance p-value Evaluated (µg/L/yr) Locks-Salmon Bay 1997–2013 ⇩ ** 0.0013 –0.105 Fremont–NW Lake 1986–2008 ‐‐ n.s. 0.9999 0.003 Union 1997–2008 ⇩ * 0.0635 –0.066 1985–2013 ⇧ * 0.0715 0.029 Dexter–SW Lake Union 1997–2013 ⇩ ** 0.0349 –0.076 NE Lake Union– 1986–2008 ‐‐ n.s. 0.9226 0.003 Portage Bay 1997–2008 ⇩ * 0.0571 –0.088 Montlake Cut 1997–2013 ‐‐ n.s. 0.1249 –0.029 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

3.6 Nutrients

In 1998 and 2006, substantial changes were made to the methods and instrumentation used for analyzing total phosphorus, total nitrogen, orthophosphate, ammonia, and nitrate + nitrite‐N. In order to conduct long‐term trend analysis, data were corrected using the regression coefficients in King County (2016).

King County 3–35 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

The Dexter–SW Lake Union sampling site was used in evaluating nutrient profiles because it is the only station where the maximum depth is greater than the typical depth of the thermocline.

3.6.1 Nitrogen Nitrogen is a major factor in the productivity of fresh waters. The major nitrogen constituents analyzed by King County are nitrate+ nitrite‐N, ammonia‐N, and total nitrogen.

The main sources of nitrogen are surface water and groundwater input and nitrogen‐ fixation by bacteria. Sewage and fertilizers contain high concentrations of nitrogen. Nitrogen fixation in fresh water is far less significant and substantial than in terrestrial soils. However, nitrogen‐limited conditions in a waterbody may give nitrogen‐fixing bacteria, such as cyanobacteria, an advantage over other phytoplankton.

Figure 3‐20 depicts the generalized nitrogen cycle in freshwater systems. In lakes, the distribution of the forms of nitrogen largely depends on the distribution of DO. The cycle relies on reduction‐oxidation by bacteria and assimilation and excretion by algae and aquatic plants.

In aerobic conditions, nitrogen gas is fixed by bacteria and is incorporated into cellular tissue. Bacteria decompose the organic nitrogen that is excreted into ammonium (NH4+) in either an aerobic or anaerobic environment. In aerobic conditions, ammonia can be further oxidized to nitrate and nitrite (nitrification) or nitrous oxide (N2O). (N2O rapidly reduces to N2 and leaves the system.) Organisms can assimilate and reduce nitrate and nitrite, which requires the energy generated via photosynthesis; ammonia does not require such reduction and is readily assimilated without energy expense.

In anaerobic environments such as the hypolimnion of lakes, nitrate is reduced to nitrite and then into nitrogen gas by anaerobic bacteria. This denitrification process is a primary vector for the loss of nitrogen from aquatic environments. Ammonia/ammonium accumulates in the oxygen‐depleted stratum because of the absence of nitrification and the reduction and release of sediment‐bound ammonium.

King County 3–36 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-20. Generalized nitrogen cycle in fresh water (source: University of Michigan, 2014).

Nitrate + Nitrite-N

Nitrate and nitrite (NO3‐/NO2‐) ions are dissolved inorganic forms of nitrogen. King County analyzes nitrate and nitrite together, and concentrations are reported as a single value of nitrogen contained in nitrate + nitrite‐N. In March 2009, the method detection limit (MDL) was lowered from 0.02 mg/L to 0.01 mg/L.

Current Conditions For the three monitoring sites that were sampled through 2013, the 2009–2013 concentrations of nitrate + nitrite‐N in the epilimnion were significantly different (Peto & Peto modification of the Gehan‐Wilcoxon test p‐value = 0.043) (Figure 3‐21). The distribution of nitrate + nitrite‐N concentrations was significantly lower at the Dexter–SW Lake Union site than at the Locks–Salmon Bay and Montlake Cut sites. The depressed concentrations at Dexter may be due to uptake of nitrate + nitrite‐N by resident phytoplankton; the high flow at the Locks and Montlake may prevent phytoplankton abundance from reaching the level in the stiller south Lake Union. In summer, the Locks site has significantly higher concentrations than the other two sites (p‐values < 0.035).

Concentrations ranged from less than 0.01 mg/L (MDL) to 0.217 mg/L (Table 3‐14). Hypolimnetic concentrations were significantly greater than epilimnetic concentrations (p‐value < 0.0001), but all values throughout the water column were low once the thermocline was established; this difference is likely due to depletion of nitrate + nitrite‐N in the spring and early summer because of phytoplankton uptake in the euphotic zone just before and during the onset of stratification.

King County 3–37 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-21. Nitrate + nitrite-N epilimnion concentrations in Lake Union/Ship Canal (2009–2013). Dashed line is the upper method detection limit (MDL); solid line is the lower MDL. Concentrations below MDL were generated using regression-on-order statistics.

Table 3-14. Nitrate + nitrite-N concentrations (mg/L) in Lake Union/Ship Canal (2009–2013). Min. Max. Site Depth FOD Min. Max. Median Mean MDL MDL Locks–Salmon Epilimnion 156/202 < MDL 0.22 0.043 0.071 0.01 0.02 Bay Epilimnion 125/187 < MDL 0.208 0.025 0.060 0.01 0.02 Dexter–SW Hypolimnion 164/187 < MDL 0.209 0.078 0.079 0.01 0.02 Lake Union Volume- 90/101 < MDL 0.208 0.049 0.075 0.01 0.02 weighted Montlake Cut Epilimnion 145/202 < MDL 0.217 0.045 0.075 0.01 0.02

FOD = frequency of detection; MDL = method detection limit.

Figure 3‐22 displays the nitrate + nitrite‐N profile over the course of the year using median 2009–2013 values from the Dexter–SW Lake Union site. Prior to stratification, nitrate + nitrite‐N is homogenous throughout the water column; the highest concentrations occur during winter. As the growing season intensifies in March and April, nitrate + nitrite‐N is depleted from the lake’s surface faster than at depth. In summer, nitrogen may be limiting algal growth and any bioavailable nitrogen (nitrate, nitrite, and ammonia) is quickly assimilated. With the establishment of the thermocline and the anoxic hypolimnion, the nitrate + nitrite‐N remaining at depth is reduced. The relatively higher concentration at 7 m to 11 m in July and August shown in Figure 3‐22 is likely an artifact of natural variability. With fall turnover, nitrate + nitrite‐N content increases and equalizes throughout the water

King County 3–38 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

as ammonia is released from the hypolimnion and is either oxidized by bacteria and archaea or assimilated by phytoplankton in the fall bloom. When primary productivity decreases in the winter, the concentration of nitrate + nitrite‐N increases as demand by phytoplankton decreases.

Figure 3-22. Time-depth isopleths of median monthly nitrate +nitrite-N concentrations at the Dexter–SW Lake Union site (2009–2013).

Long‐Term Trends To determine nitrate + nitrite‐N trends, 1,000 permutations of the Seasonal Mann‐Kendall test were run with values below the MDL substituted with potential values. Nitrate + nitrite‐N concentrations were volume‐weighted. Table 3‐15 presents the results for the annualized trend analysis. Interquartile ranges for the p‐values and slope magnitudes are presented. The third quartile p‐value was used to determine trend significance.

The analysis demonstrates significant annualized downward trends in nitrate + nitrite‐N at the Locks–Salmon Bay, Dexter–SW Lake Union, and Montlake Cut sites (Table 3‐15); these trends were not detected at the Fremont–NW Lake Union and NE Lake Union–Portage Bay sites, which had fewer sampling years. The downward trends were detected during fall, winter, and spring; the significance of the trends was greatest in fall and spring.

Annually, nitrate + nitrite‐N concentrations are decreasing at a rate between 0.80 ppb and 1.04 ppb (approximately 0.001 mg/L) per year, which is ecologically insubstantial but may reflect a trend of decreased nutrient loading to Lake Union/Ship Canal. The magnitudes of the slope for concentrations at the Montlake Cut site were comparable to slopes from the downstream sites, which suggests there may be decreased nitrogen loading from Lake Washington but not necessarily from the immediate Lake Union/Ship Canal watershed.

King County 3–39 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table 3-15. Seasonal Mann-Kendall trends for volume-weighted nitrate + nitrite-N concentrations in Lake Union/Ship Canal. Interquartile ranges for p-values and slope magnitude from 1,000 permutations are presented. Years Magnitude Site Direction Significance p-value Evaluated (ppb/yr) 0.0003 – –0.99 to Locks-Salmon Bay 1976–2013 *** ⇩ 0.0006 –1.04 Fremont–NW Lake 0.1971 – –0.80 to 1992–2008 n.s. Union ‐‐ 0.2680 –0.93 Dexter–SW Lake 0.0111 – –0.90 to 1985–2013 ** Union ⇩ 0.0156 –0.96 NE Lake Union– 0.0872 – –0.83 to 1992–2008 n.s Portage Bay ‐‐ 0.1616 –1.04 0.0001 – –0.93 to Montlake Cut 1976-–2013 *** ⇩ 0.0002 –0.99 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

Ammonia-N

Ammonia in fresh water is found predominately ionized as ammonium (NH4+), a readily assimilated form of inorganic nitrogen. The analytical method employed by King County reports the combined concentration of ammonia‐N and ammonium‐N.

Organisms assimilate ammonia into their structures, using the nitrogen as a building block for amino acids, nucleotides, and other organic compounds. These organisms excrete inorganic ammonia and organic nitrogen compounds. Unlike nitrate and nitrite, ammonia does not require energy expenditure to reduce and assimilate the compound. Phytoplankton will preferentially take up nitrogen in the reduced ammonia form.

Current Conditions From 2009 through 2013, ammonia concentrations in the epilimnion of the three sites monitored through 2013 were not significantly different (Peto & Peto modification of the Gehan‐Wilcoxon test p‐value = 0.219) (Figure 3‐23). However, in winter, the Locks–Salmon Bay and Montlake Cut sites had significantly higher concentrations than did the Dexter–SW Lake Union site (p‐value = 0.0042).

Concentrations of ammonia ranged from less than 0.002 mg/L to 2.09 mg/L (Table 3‐16). At the Dexter–SW Lake Union site, hypolimnetic concentrations were significantly greater than epilimnetic concentrations (p‐value < 0.0001). This difference is likely due to the influence of hypolimnetic anoxia. In August 2013, the MDL for ammonia‐N was lowered from 0.005 mg/L to 0.002 mg/L.

King County 3–40 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-23. Epilimnion ammonia concentrations in Lake Union/Ship Canal (2009–2013). Dashed line is the upper method detection limit (MDL); solid line is the lower MDL. Concentrations below MDL were generated using regression-on-order statistics.

Table 3-16. Ammonia concentrations (mg/L) in Lake Union/Ship Canal (2009–2013). Min. Max. Site Depth FOD Min. Max. Median Mean MDL MDL Locks– Epilimnion 150/216 < MDL 0.0498 0.0084 0.0109 0.002 0.005 Salmon Bay Epilimnion 99/199 < MDL 0.0531 0.0023 0.0083 0.002 0.005 Dexter–SW Hypolimnion 166/199 < MDL 2.09 0.0170 0.1467 0.002 0.005 Lake Union Volume- 88/108 < MDL 0.541 0.0189 0.0738 0.002 0.005 weighted Montlake Cut Epilimnion 148/216 < MDL 0.161 0.0065 0.0117 0.002 0.005

FOD = frequency of detection; MDL = method detection limit.

Figure 3‐24 depicts ammonia concentrations over the course of the year using median 2009–2013 values from the Dexter–SW Lake Union site. Prior to stratification, ammonia is homogenous and near the MDL throughout the water column. With the establishment of the thermocline and the anoxic hypolimnion, ammonia begins to accumulate in the hypolimnion as nitrogen enters the hypolimnion in particulate form and decomposes to ammonia released into the water column. Once the thermocline disappears in November, ammonia is oxidized to nitrate + nitrite‐N and flushed from the system.

King County 3–41 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-24. Time-depth isopleths of median monthly ammonia concentrations at the Dexter– SW Lake Union site (2009–2013). Note log-scale.

Comparison to Criteria Because un‐ionized ammonia (NH3) can be toxic to aquatic species, Ecology has established criteria based on pH, temperature, and presence of salmonids (WAC 173‐201A‐240). The activity of un‐ionized ammonia depends on pH and ionic strength (conductivity); toxicity increases with increasing pH and decreases with increasing conductivity (Bower and Bidwell, 1978; Alabaster et al., 1979; Harader and Allen, 1983).

Ammonia concentrations were examined in Lake Union/Ship Canal for potential exceedances of the criteria. From 2004 through 2013, the chronic criterion for when salmonids are present was exceeded once on September 6, 2006, at a depth of 14 m at the Dexter–SW Lake Union site. The observed total ammonia was 2.20 mg/L; the chronic criterion that corresponds to the ambient temperature and pH (13.1°C and 6.9, respectively) was 2.13 mg/L. The conductivity at the time and depth of sampling was 1,600 µmhos/cm (a salinity of ~0.8 ppt), indicating that the sample was taken from the saltwater layer. Because of the high conductivity and nearly neutral pH, very little of the ammonia was likely to be un‐ionized (approximately 0.004 mg/L) and, thus, the high concentration would not likely pose a substantial toxicity threat to salmonids.

Long‐Term Trends To determine ammonia trends, 1,000 permutations of the Seasonal Mann‐Kendall test were run with concentrations below the MDL substituted with potential concentrations. Ammonia concentrations were volume‐weighted. Table 3‐17 presents the results for the annualized trend analysis. Interquartile ranges for the p‐values and slope magnitudes are presented. The third quartile p‐value was used to determine trend significance.

King County 3–42 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Generally, ammonia concentrations in Lake Union/Ship Canal have decreased significantly at annual rates between 0.1 ppb and 0.45 ppb (0.0001 mg/L and 0.00045 mg/L) (Table 3‐17). On an annual basis, significant downward trends were observed at the Locks–Salmon Bay, Fremont–NW Lake Union, and Montlake Cut sites. Similar to nitrate + nitrite‐N, significant downward trends were detected only in the wet‐weather months, likely because ammonia was not commonly detected in the dry season when primary productivity is high. For all seasons, the magnitudes of the slope for concentrations at the Montlake Cut site were not as steep as the slopes for the downstream sites, suggesting that there may be decreased ammonia loading over time from Union Bay and from the immediate Lake Union/Ship Canal watershed.

Table 3-17. Seasonal Mann-Kendall trends for volume-weighted ammonia concentrations. Interquartile ranges for p-values and slope magnitude from 1,000 permutations are presented. Years Magnitude Site Direction Significance p-value Evaluated (ppb/yr) –0.263 to Locks–Salmon Bay 1976–2013 *** 0.0080 – 0.0014 ⇩ –0.274 Fremont–NW Lake –0.407 to 1992–2008 ** 0.0185 – 0.0276 Union ⇩ –0.451 Dexter–SW Lake –0.209 to 1985–2013 n.s. 0.1038 – 0.1258 Union ‐‐ –0.222 NE Lake Union– –0.246 to 1992–2008 n.s. 0.0558 – 0.1229 Portage Bay ‐‐ –0.303 –0.104 to Montlake Cut 1976–2013 ** 0.0092 – 0.0216 ⇩ –0.117 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

Total Nitrogen Total nitrogen is a measure of all nitrogen in ambient water, whether as a soluble ion, bound to sediment, assimilated in phytoplankton, or in any other form. Total nitrogen values provide insight into the amount of nitrogen cycling through the ecologic system.

Current Conditions From 2009 through 2013, the Locks–Salmon Bay site had significantly higher concentrations of total nitrogen than the Dexter–SW Lake Union and Montlake Cut sites, which were statistically different (Kruskal‐Wallis p‐value = 0.053) (Figure 3‐25).

Total nitrogen concentrations ranged from 0.161 mg/L to 2.01 mg/L (Table 3‐18). Hypolimnetic concentrations were significantly greater than epilimnetic concentrations (p‐value < 0.0001), likely because of the influence of hypolimnetic anoxia on the release of nitrogen from the sediments and the input of particulate nitrogen as it falls from the epilimnion.

King County 3–43 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-25. Epilimnion total nitrogen concentrations in Lake Union/Ship Canal (2009–2013).

Table 3-18. Total nitrogen concentrations (mg/L) in Lake Union/Ship Canal (2009–2013). Min. Max. Site Depth FOD Min. Max. Median Mean MDL MDL Locks–Salmon Epilimnion 202/202 0.195 0.403 0.274 0.281 0.05 0.05 Bay Epilimnion 187/187 0.161 0.647 0.262 0.273 0.05 0.05 Dexter–SW Lake Hypolimnion 187/187 0.183 2.01 0.304 0.413 0.05 0.05 Union Volume- 101/101 0.198 0.709 0.312 0.342 0.05 0.05 weighted Montlake Cut Epilimnion 202/202 0.173 0.394 0.269 0.270 0.05 0.05

FOD = frequency of detection; MDL = method detection limit.

Figure 3‐26 depicts total nitrogen concentrations over the course of the year using median 2009–2013 values for the Dexter–SW Lake Union site. The pattern is similar to that of ammonia. During the period of stratification in the summer, particulate nitrogen and ammonia constitute the majority of total nitrogen in the hypolimnion. At the surface, total nitrogen concentrations increase with the start of the growing season in March, peaking in August and September. During the summer months, nitrate + nitrite‐N and ammonia concentrations at the surface are close to or below the detection limits; the vast majority of the total nitrogen, therefore, must be in organic form or bound to suspended sediments. After the thermocline is fully degraded, nitrogen is quickly flushed from the system at the onset of fall rains.

King County 3–44 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-26. Time-depth isopleths of median monthly total nitrogen concentrations at the Dexter–SW Lake Union site (2009–2013). Note log-scale.

Long‐Term Trends Volume‐weighted total nitrogen concentrations were used to evaluate trends for Lake Union/Ship Canal. Table 3‐19 presents the results for the annualized trend analysis. Overall, total nitrogen concentrations decreased during the study period, although only the Locks–Salmon Bay and Montlake Cut sites had significant downward trends on an annual basis. These sites had consistent downward trends for all seasons, except for in the spring season when the Locks site was just above the level of significance (p‐value = 0.1110).

For all seasons, the slopes of decrease in concentrations at the Locks–Salmon Bay site were steeper than the slopes for the upstream sites, suggesting decreased total nitrogen loading from Lake Washington and an even greater decrease in loading from the immediate Salmon Bay watershed. The slopes for the Fremont–NW Lake Union, Dexter–SW Lake Union, and NE Lake Union–Portage Bay sites were less steep and less significant than those for the Locks–Salmon Bay and Montlake Cut sites; this difference may be due to the shorter sampling period for the Fremont and NE Lake Union sites and the variability of total nitrogen in Lake Union as the result of the inconstant phytoplankton abundance.

Total nitrogen trend slopes are one to two orders of magnitude greater than ammonia and nitrate + nitrite‐N slopes. The differences in slope magnitudes suggest that the majority of the decrease in the nitrogen concentration in Lake Union/Ship Canal is in the form of particulate or organic nitrogen and not in the dissolved fraction.

King County 3–45 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table 3-19. Seasonal Mann-Kendall trends for volume-weighted total nitrogen concentrations in Lake Union/Ship Canal. Years Magnitude Site Direction Significance p-value Evaluated (ppb/yr) Locks–Salmon Bay 1993–2013 ⇩ *** 0.0031 –4.20 Fremont–NW Lake 1993–2008 -- n.s. 0.1230 –2.81 Union Dexter–SW Lake Union 1993–2013 -- n.s. 0.1113 –2.53 NE Lake Union–Portage 1993–2008 -- n.s. 0.1961 –2.08 Bay Montlake Cut 1993–2013 ⇩ ** 0.0129 –2.97

Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

3.6.2 Phosphorus Phosphorus, similar to nitrogen, is a crucial nutrient for primary productivity, but its limited abundance in fresh water often makes it the limiting nutrient for growth of freshwater phytoplankton. Phosphorus is necessary for many critical biologic structures, including nucleotides, phospholipids, and adenosine triphosphate (ATP).

Total phosphorus represents both organic and inorganic phosphorus in particulate and dissolved forms.8 Generally, the majority of total phosphorus is found in organic forms; during stratification, however, inorganic orthophosphate (PO43‐) may become the dominant species in the hypolimnion. Orthophosphate is the only significant form of inorganic phosphorus in lakes.

Particulate phosphorus is found in organisms and in, or strongly adsorbed to, mineral complexes such as ferric hydroxide. Dissolved phosphorus is composed primarily of ionic orthophosphate, synthetic polyphosphates, and low‐molecular‐weight organic phosphates. Both orthophosphates and polyphosphates were formerly components of cleaning detergents. Orthophosphate is present in animal waste, fertilizers, and other organic detritus. Phosphorus may also enter the water column through resuspension of sediments.

The adsorption of orthophosphate to mineral complexes is driven by pH and reduction‐ oxidation. Under aerobic conditions, some metal ions, such as iron and manganese, form amorphous hydroxide complexes with water and settle to the sediment surface; dissolved inorganic phosphorus binds to these complexes and becomes unavailable for biologic assimilation. Under anaerobic conditions, these metal hydroxides are reduced by anaerobic

bacteria and orthophosphate is released into the hypolimnion.

8 “Dissolved” means it can be passed through a 0.45‐micron membrane filter.

King County 3–46 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Orthophosphate Orthophosphate, also known as soluble reactive phosphorus, is readily available for biologic uptake. During periods of algal growth, ambient orthophosphate is seldom observed above MDLs because of its rapid assimilation. At depths below the zone of productivity, however, orthophosphate accumulates during the summer through release from sediments and decreased primary productivity. The MDL was 0.002 mg/L until August 2013, when it was lowered to 0.0005 mg/L.

Current Conditions From 2009 through 2013, orthophosphate concentrations in Lake Union/Ship Canal ranged from less than 0.0005 mg/L to 1.1 mg/L (Table 3‐20). Concentrations were significantly higher at the Locks–Salmon Bay site than at the Dexter–SW Lake Union and Montlake Cut sites (Peto & Peto modification of the Gehan‐Wilcoxon test p‐value = 0.0007) (Figure 3‐27).

The higher concentrations at the Locks site may be explained by a relatively lower rate of primary productivity and greater local external loading relative to upstream sites; however, similar concentrations of chlorophyll a were found at the Locks and Dexter sites, suggesting similar rates of productivity. Inputs of stormwater, CSOs, and marine water from Locks operations may be a source of phosphorus loading. From June to December 2010, surface orthophosphate concentrations at Shilshole Bay downstream of the Locks– Salmon Bay site ranged from 0.0352 mg/L to 0.0539 mg/L, an order of magnitude greater than the median concentrations seen in fresh water (King County, unpublished data).

Table 3-20. Orthophosphate concentrations (mg/L) in Lake Union/Ship Canal (2009–2013).

Min. Max. Site Depth FOD Min. Max. Median Mean MDL MDL Locks–Salmon Epilimnion 103/202

FOD = frequency of detection; MDL = method detection limit. Figure 3‐28 depicts orthophosphate concentrations over the course of the year at the Dexter–SW Lake Union site using 2009–2013 median values. Concentrations are low throughout the year and water column until the establishment of the hypolimnion. The concentration of orthophosphate in the hypolimnion quickly reaches more than 20 times that of the epilimnion. In the epilimnion, concentrations peak during winter, when low productivity and increased surface runoff occur. As the growing season begins in March and April, orthophosphate in the euphotic zone is quickly depleted. Following fall turnover, concentrations increase in the epilimnion as the phosphorus‐rich hypolimnetic water is mixed throughout the water column. This orthophosphate leaves the water column as the result of flushing with increased hydraulic input, which promotes adsorption to the newly

King County 3–47 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal oxidized metal ions and subsequent sedimentation, or as the result of a late‐season algal bloom that assimilates upsurged nutrients.

Figure 3-27. Orthophosphate epilimnion concentrations in Lake Union/Ship Canal (2009–2013). Dashed line is the upper method detection limit (MDL); solid line is the lower MDL. Values below the MDL were generated using regression-on-order statistics. Note log-scale. Values in µg/L (mg/L*10-3).

Figure 3-28. Time-depth isopleths of median monthly orthophosphate concentrations at the Dexter–SW Lake Union site (2009–2013). Note log-scale.

King County 3–48 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Long‐Term Trends To determine orthophosphate trends, 1,000 permutations of the Seasonal Mann‐Kendall test were run with values below the MDL substituted with potential values. Concentrations were volume‐weighted.

Table 3‐21 presents the results for the annualized trend analysis. Interquartile ranges for the p‐values and slope magnitudes are presented. The third quartile p‐value was used to determine trend significance. Much variation is seen in the significance and slopes for trends in orthophosphate because of the large number of samples below the MDL, especially in the summer and spring.

On an annual basis, orthophosphate concentrations have decreased significantly at all sites. The greatest decreases were seen in summer, fall, and winter, ranging from 0.144 ppb to 0.621 ppb per year (0.0001 mg/L to 0.0006 mg/L). This finding suggests decreased orthophosphate loading over time from Lake Washington and from the immediate Lake Union/Ship Canal watershed.

For winter, the slopes for the Locks–Salmon Bay, NE Lake Union–Portage Bay, and Montlake Cut sites were comparable and greater than the slopes observed at the Fremont– NW Lake Union and Dexter–SW Lake Union sites. Orthophosphate concentrations were generally higher at the Locks, NE Lake Union, and Montlake sites in the late 1980s and early 1990s, perhaps because of the higher flow velocity that prevented sedimentation and sustained algal productivity. The lower flow velocity at the Fremont and Dexter sites may have allowed the binding and assimilation of the orthophosphate ions.

Table 3-21. Seasonal Mann-Kendall trends for volume-weighted orthophosphate concentrations in Lake Union/Ship Canal. Interquartile ranges for p-values and slope magnitude from 1,000 permutations are presented. Years Magnitude Site Direction Significance p-value Evaluated (ppb/yr) –0.249 to Locks–Salmon Bay 1986–2013 *** < 0.0001 ⇩ –0.255 Fremont–NW Lake –0.274 to 1992–2008 *** 0.0005 – 0.0009 Union ⇩ –0.283 Dexter–SW Lake –0.200 to 1985–2013 *** < 0.0001 – 0.0001 Union ⇩ –0.206 NE Lake Union– –0.176 to 1992–2008 *** 0.0013 – 0.0029 Portage Bay ⇩ –0.191 -0.106 to Montlake Cut 1986-2013 *** < 0.0001 – 0.0001 ⇩ –0.121 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

King County 3–49 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Total Phosphorus

Current Conditions From 2009 through 2013, total phosphorus concentrations in Lake Union/Ship Canal ranged from less than 0.005 mg/L to 1.35 mg/L (Table 3‐22). Concentrations at the Locks–Salmon Bay and Dexter–SW Lake Union sites were significantly greater than concentrations at the Montlake Cut site (Figure 3‐29); seasonally, this difference was found for summer and fall.

Figure 3‐30 depicts concentrations of total phosphorus at the Dexter‐SW Lake Union site over the course of the year using median 2009–2013 values for the water column. The greatest values of total phosphorus were observed during the late summer and early fall at all depths, although higher values were also observed in March and April. As seen with orthophosphate, total nitrogen, and ammonia, total phosphorus peaks in the hypolimnion during stratification with the accumulation of organic detritus and the release of inorganic phosphorus from the sediments. In the epilimnion, total phosphorus is greatest in March/April and September/October, associated with spring and fall phytoplankton blooms and increased wet‐weather events.

Lake Union/Ship Canal is on the 303(d) list for total phosphorus for exceeding a summer (June through September) mean epilimnetic concentration of 20 µg/L in 2004, 2005, and 2006 at the Dexter−Lake Union site. However, analysis of total phosphorus in Lake Union/Ship Canal found a mean summer epilimnetic concentration (2009−2013) of 14.6 µg/L at the same site. Additionally, reanalysis of 2004, 2005, and 2006 data indicates that the mean epilimnetic concentrations were below the criteria (13.4, 13.5, and 13.1 µg/L, respectively). These findings suggest that the current 303(d) listing is unwarranted and may be due to an analytical error, such as including hypolimnetic total phosphorus measurements. The proposed Water Quality Assessment and Candidate 303(d) list submitted to EPA by Ecology has removed the total phosphorus listing for Lake Union/Ship Canal.

Table 3-22. Total phosphorus concentrations (mg/L) in Lake Union/Ship Canal (2009–2013). Min. Max. Site Depth FOD Min. Max. Median Mean MDL MDL Locks–Salmon Bay Epilimnion 202/202 0.008 0.065 0.014 0.015 0.005 0.005 Epilimnion 273/273 0.005 0.071 0.014 0.015 0.005 0.005 Dexter–SW Lake Hypolimnion 187/187 0.006 1.35 0.014 0.089 0.005 0.005 Union Volume- 101/101 0.006 0.357 0.015 0.0500 0.005 0.005 weighted Montlake Cut Epilimnion 197/202 < 0.005 0.026 0.012 0.013 0.005 0.005

FOD = frequency of detection; MDL = method detection limit.

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Figure 3-29. Epilimnion total phosphorus concentrations in Lake Union/Ship Canal (2009–2013).

Figure 3-30. Time-depth isopleths of median monthly total phosphorus concentrations at the Dexter–SW Lake Union site (2009–2013). Note log-scale.

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Long‐Term Trends Volume‐weighted total phosphorus concentrations were used to evaluate trends for Lake Union/Ship Canal. Concentrations are decreasing significantly for all sites, with annual rates ranging from 0.08 ppb to 0.27 ppb (0.00008 mg/L to 0.00027 mg/L) (Table 3‐23). For individual seasons, downward slopes ranged from 0.1 ppb to 1.2 ppb per year (0.0001 mg/L to 0.0012 mg/L). This decline in total phosphorus is most noticeable during winter months, which are marked by wet‐weather events and low primary productivity.

The less apparent trends in spring, summer, and fall may be due to variable phytoplankton blooms, sediment loading, internal loading, and the ability to capture and adequately represent these spatiotemporal variations with monthly and bimonthly discrete samples. In well‐mixed winter conditions, total phosphorus concentrations are likely to be more evenly distributed.

In winter and spring, the slope magnitude for the Montlake Cut site was lower than those for the downstream sites; in summer, all sites downstream of the Montlake site, except the Locks–Salmon Bay site, had greater magnitudes than at Montlake; and in fall, the Locks– Salmon Bay and Fremont–NW Lake Union sites had greater magnitudes than the other three sites. These trends suggest that phosphorus loading from the immediate Lake Union/Ship Canal watershed is decreasing at a greater rate than loading from Lake Washington.

Table 3-23. Seasonal Mann-Kendall trends for volume-weighted total phosphorus concentrations in Lake Union/Ship Canal. Years Magnitude Site Direction Significance p-value Evaluated (ppb/yr) Locks–Salmon Bay 1986–2013 ⇩ *** 0.0003 –0.200 Fremont–NW Lake 1992–2008 *** 0.0060 –0.270 Union ⇩ Dexter–SW Lake Union 1985–2013 ⇩ *** 0.0083 –0.194 NE Lake Union– 1992–2008 ⇩ *** 0.0060 –0.150 Portage Bay Montlake Cut 1986–2013 ⇩ *** 0.0008 –0.080 Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

3.6.3 Silica Silica is a necessary nutrient for diatoms (Bacillariophyta), some chrysophytes, aquatic sponges, and other organisms. Diatoms are the dominate user of silica, assimilating great quantities for the synthesis of their skeletal structure. Major sources of silica are groundwater input and riverine influent containing weathered bedrock.

As diatoms deteriorate with age and fall to the bottom, they settle and become incorporated into the sediments. This process leads to a seasonal succession of dominance by different species of diatoms based on efficiency of silica assimilation and on growth

King County 3–52 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal rates. At low silica levels (< 0.5 mg/L), other algae that do not depend on high levels of dissolved silica will dominate. Silica limitation in lakes occurs most commonly during late spring through summer, but silica does not appear to be limiting in Lake Union/Ship Canal.

Current Conditions From 2009 through 2013, silica concentrations in Lake Union/Ship Canal ranged from 1.62 mg/L to 8.44 mg/L (Table 3‐24). The Montlake Cut site had slightly greater concentrations than the other two sites sampled through 2013 (Kruskal‐Wallis p‐value = 0.0768) (Figure 3‐31). This difference stems from higher silica concentrations at the Montlake site than at the Locks–Salmon Bay and Dexter–SW Lake Union sites in the summer (Kruskal‐Wallis p‐value = 0.0004); during all other seasons, concentrations were statistically indistinguishable (Kruskal‐Wallis p‐values > 0.30).

Figure 3‐32 depicts 2009–2013 silica concentrations over the course of the year at the Dexter–SW Lake Union site. Unlike other nutrients, silica was sampled only in the epilimnion at Dexter. Silica concentrations peak in February and March, just prior to the growing season. Once the growing season begins, silica steadily declines until June and then remains stable at approximately 3.5 mg/L until September and October. It appears that concentrations of silica during winter are controlled by input from Union Bay and/or local stormwater inputs of eroded soils rather than by diatom uptake.

Table 3-24. Silica concentrations (mg/L) in Lake Union/Ship Canal (2009–2013). Min. Max. Site Depth FOD Min. Max. Median Mean MDL MDL Locks–Salmon Bay Epilimnion 198/198 1.74 8.09 4.52 4.74 0.05 0.05 Dexter–SW Lake Epilimnion 187/187 1.62 8.09 4.43 4.71 0.05 0.05 Union Hypolimnion 2/2 5 5.16 5.08 5.08 0.05 0.05 Montlake Cut Epilimnion 198/198 2.11 8.44 4.63 5.01 0.05 0.05

FOD = frequency of detection; MDL = method detection limit.

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Figure 3-31. Silica epilimnion concentrations in Lake Union/Ship Canal (2009–2013).

Figure 3-32. Monthly epilimnion silica concentrations at the Dexter–SW Lake Union site (2009– 2013).

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Long-Term Trends There are not sufficient data to conduct long‐term trend analysis of silica concentrations in Lake Union/Ship Canal. Silica sampling began in 2002 at the Dexter–SW Lake Union site and in 2009 at the Locks–Salmon Bay and Montlake Cut sites.

Data show a slight positive but statistically insignificant trend in annual epilimnetic silica concentrations from 2002 through 2013 (Appendix C). USACE’s false locking experiment in 2013 allowed substantially more salt water to enter the Lake Union/Ship Canal system. In 2002, a large saltwater incursion also occurred and a corresponding increase in silica was not seen in epilimnion silica concentrations.

3.7 Trophic State Indices and Limiting Factors for Phytoplankton

This section evaluates the trophic state of Lake Union/Ship Canal and the potential factors that may be limiting phytoplankton growth and abundance:  Trophic state indices (TSIs) were developed by Carlson (1977). They provide a way to rate and compare lakes on a scale from 0 through 100 according to their level of biological activity. Trophic state is the gross amount of living biological matter in a waterbody at a point in time. It is the result of internal and external forces such as nutrient loading, seasonality, and grazing. The calculation of trophic state is closely related to phytoplankton biomass.  Phytoplankton communities in lakes are greatly influenced by ambient physical and chemical conditions and by biotic factors such as zooplankton grazing and competition between species. These factors may limit or favor certain phytoplankton species.

3.7.1 Trophic State Indices TSIs assist in the general classification of lakes based on the level of primary productivity. They use three measures as proxies for the lake trophic state: total phosphorus (TP), Secchi transparency, and chlorophyll a. The estimated trophic state is used to assign qualitative indicators of condition: eutrophic (high), mesotrophic (medium or moderate), or oligotrophic (low) (Table 3‐25). The following equations are used for calculating TSI values:

2.04 0.68 ∗ ln . 10 ∗ 6 ln2 ln . 10 ∗ 6 ln2 ln48⁄ . 10 ∗ 6 ln2

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Where: Chl is the chlorophyll a concentration in µg/L SD is the Secchi depth in m TP is the total phosphorus concentration in µg/L.

Table 3-25. Description of trophic state index (TSI) classifications. TSI Valuea Classification Characterization < 30–40 Oligotrophic High water clarity and low chlorophyll and phosphorus concentrations, representing low biological activity. 40–50 Mesotrophic Moderate water clarity, chlorophyll a, and phosphorus concentrations, representing medium biological activity > 50 Eutrophic Low water clarity and high chlorophyll and phosphorus concentrations, representing high biological activity a Range of TSI transformed values.

The differences (“residuals”) between values for the TSI variables may provide additional insight into lake conditions that are affecting phytoplankton biomass:  Highly colored lakes that contain large amounts of dissolved organic matter may produce high TSI ratings for Secchi transparency (TSI.SD > TSI.Chl). (This is not the case for Lake Union/Ship Canal.)  The shape and size of dominant phytoplankton species can influence the Secchi reading and chlorophyll a values, because small, diffuse algae tend to cloud the water more than large, dense algal colonies. If large species dominate, then the TSI.Chl will be greater than the TSI.SD.  Zooplankton grazing can increase transparency and reduce chlorophyll a concentrations (TSI.SD = TSI.TP > TSI.Chl).  Phosphorus limitation can be seen as TSI.SD = TSI.Chl > TSI.TP.  Algal‐dominated light limitation can be seen as TSI.SD = TSI.Chl = TSI.TP.

Figures 3‐33 and 3‐34 plot the 1985–2013 values used to determine the TSI for the Lake Union epilimnion (Dexter–SW Lake Union site) during the growing season (March through June) and during months of greatest stratification (July through September). Most of the values fell within the mesotrophic TSI. Tomlinson et al. (1977) also concluded that Lake Union was mesotrophic, which suggests that its trophic state has not substantially shifted over the past 40 years.

Table 3‐26 shows trends in TP, chlorophyll a, and Secchi transparency TSI values for spring and summer at the Dexter–SW Lake Union site for the same period (1985–2013). Linear regressions over time showed significant trends for TP and chlorophyll a in the summer months; the median summer value increased by 0.218 units per year for chlorophyll a and decreased by 0.094 units per year for TP. No significant trends were detected for Secchi transparency for either spring or summer, and no significant trends were detected during the growing season (March through June) for any index.

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Figure 3-33. Epilimnion spring (March – June) trophic state index at the Dexter–SW Lake Union site (1985–2013).

Figure 3-34. Epilimnion summer (July – September) trophic state index at the Dexter–SW Lake Union site (1985–2013).

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Trends were also evaluated for 1997–2013 (Table 3‐27) because a substantial shift in chlorophyll a concentrations was observed in the mid‐1990s. An apparent increasing trend in spring concentrations reversed during that time and began to gradually decline. No significant summer trends were observed for any of the parameters; however, spring TP and chlorophyll a TSI values showed significant negative trends of 0.228 and 0.523 units per year, respectively. No significant trend for Secchi transparency was observed.

Table 3-26. Spring and summer trophic state index value trends for total phosphorus, chlorophyll a, and Secchi transparency for the Dexter–SW Lake Union site (1985– 2013). Magnitude Season Index Direction Significance p-value (unit yr-1) Total ⇩ * 0.0814 –0.094 phosphorus Summer Chlorophyll a ⇧ ** 0.0147 0.218 Secchi -- n.s. 0.8688 –0.006 transparency Total -- n.s. 0.3181 0.050 phosphorus Spring Chlorophyll a -- n.s. 0.7724 0.017 Secchi -- n.s. 0.9533 –0.002 transparency Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

Table 3-27. Spring and summer trophic state index value trends for total phosphorus, chlorophyll a, and Secchi transparency for the Dexter–SW Lake Union site (1997– 2013). Magnitude Season Index Direction Significance p-value (unit yr-1) Total -- n.s. 0.8660 0.015 phosphorus Summer Chlorophyll a -- n.s. 0.5050 –0.073 Secchi -- n.s. 0.9880 –0.001 transparency Total ** 0.0377 –0.228 phosphorus ⇩ Spring Chlorophyll a ⇩ *** <0.0001 –0.523 Secchi -- n.s. 0.6276 –0.036 transparency Adjusted p‐values were calculated using three‐day prior rainfall as a covariate and corrected for inter‐ block covariance. n.s. = not significant (p > 0.10); * = marginally significant (p = 0.05‐0.10); ** = significant (p = 0.01‐0.05); *** = highly significant (p < 0.01).

TSI residuals were plotted to gain insight into factors other than TP that may be limiting chlorophyll a. Figure 3‐35 presents 1985–2013 residuals for the Dexter–SW Lake Union site during summer. Chlorophyll a TSI values are consistently greater than Secchi transparency and TP TSI values; a similar relationship occurs in the spring when only 1997–2013 data are used. Possible reasons for these discrepancies are as follows:

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 Greater chlorophyll a than Secchi transparency values suggests that the dominance of large diatoms such as Tabellaria and Stephanodiscus spp. in spring, fall, and (to lesser extents) summer and winter skews the residual between chlorophyll a and Secchi transparency TSIs because of the smaller impact of large diatoms on transparency. This discrepancy may be enhanced by the grazing of phytoplankton by zooplankton and subsequent predation of zooplankton by planktivorous fish, which increase transparency. However, limited zooplankton data preclude any conclusions in this regard.  Greater chlorophyll a than TP values suggests that productivity in Lake Union is limited by nutrient availability.

Figure 3-35. Summer Trophic state index residuals for the Dexter–SW Lake Union site (1985– 2013).

3.7.2 Limiting Factors Phytoplankton are diverse assemblages of multiple taxonomic groups. This diversity spurs a large range of physiological requirements of phytoplankton species. Potential growth‐ regulating factors for phytoplankton are light, nutrient availability (primarily phosphorus, nitrogen, and silica), and temperature. Phytoplankton abundance may be limited by zooplankton grazing and water residence time. These factors as they relate to Lake Union/Ship Canal are as follows:  Light is likely to be a limiting factor at depth.  Low temperatures reduce phytoplankton productivity in the winter. Summertime temperatures do not reach extremes that would limit productivity.

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 The relative importance of nitrogen and phosphorus is discussed in the following section. Phosphorus is typically the limiting nutrient, although both phosphorus and nitrogen may be co‐limiting in the summer.  Silica does not appear to be limiting. Silica values drop during the growing season to approximately 3 mg/L at the surface. From 2009 through 2013, however, the molar silica to total nitrogen ratio (Si:N) never dropped below 1.5 and the molar silica to total phosphorus ratio (Si:P) never dropped below 50 at the Dexter–SW Lake Union site (Table 3‐28) (Tilman et al., 1982; Hecky and Kilham, 1988; Gilpina et al., 2004). Generally, silica is considered limiting below an Si:N ratio of 1:1 or an Si:P ratio of 16:1. At high Si:P ratios, diatoms have been found to be the superior competitor for phosphorus relative to green algae (Kilham, 1986).  Limited data are available on zooplankton dynamics in Lake Union/Ship Canal, and the importance of grazing as a limiting factor is unknown (Tomlinson et al., 1977).  A transient system may exist that spatially and temporally limits the eutrophication of Lake Union. The sudden and large availability of nutrients and light in the spring and fall allows the formation of blooms, but as these blooms and nutrients are flushed through the system, phytoplankton growth and accumulation become limited by both nutrients and perhaps zooplankton grazing. The limitation to phytoplankton abundance in summer may not depend solely on the availability of nutrients or light but also on the flushing rate of the system (Dickman, 1969; Tomlinson et al., 1977). The low residence time of water in Lake Union/Ship Canal may prevent substantial standing crops of phytoplankton from building up and may also prevent some internal cycling of nutrients as particulate forms of the nutrients move down the channel and are exported.

Table 3-28. Molar Si:N and molar Si:P ratios at the Dexter–SW Lake Union site (2009–2013). Ratio n Min. Max. Median Mean Si:N 101 1.5 7.3 3.8 4.1 Si:P 101 52 455 188 184

3.7.3 Nitrogen to Total Phosphorus Ratio The ratio of total nitrogen to total phosphorus (N:P) is often accepted as an indicator of the nutrient that is limiting algal growth. The cutoff points for determining the limiting nutrient vary. Usually, lake water is considered to be nitrogen limited if the mass‐based N:P ratio is less than 10 and to be phosphorus limited if the mass‐based N:P ratio is greater than 17 (Carroll and Pelletier, 1991). Certain cyanobacteria species may have an advantage in nitrogen‐limiting conditions because they can fix molecular nitrogen.

From the start of total nitrogen sampling in 1993 until 2013, N:P ratios in spring, summer, and fall indicate that phosphorus is predominately the limiting nutrient and that phosphorus and nitrogen may be co‐limiting in some cases (Appendix C):  In spring, 80.5 percent of N:P ratios suggest that phosphorus is limiting.  In summer, 57.5 percent of N:P ratios suggest that phosphorus is limiting and a few observations indicate that nitrogen is limiting.

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 In fall, 60.0 percent of N:P ratios suggest that phosphorus is limiting. The TSI trends discussed in the previous section, however, indicate that phosphorus may not be the primary limiting factor during the summer but appears to be a substantial limiting factor in the spring, especially during the diatom bloom. Thus, phosphorus and nitrogen may be co‐limiting in that nitrogen and/or phosphorus are limiting in the summer and phosphorus is limiting during the remainder of the year.

The most recent (2009–2013) N:P ratios at the Dexter–SW Lake Union site show that phosphorus is typically limiting (annual median = 20.7); in some cases, typically in the summer and sometimes in the fall, nitrogen and phosphorus may be co‐limiting (Table 3‐ 29). The range of N:P ratios suggests that the concentrations of these nutrients are in flux and do not necessarily follow similar temporal patterns.

Table 3-29. Mass-based total nitrogen to total phosphorus ratio by season at the Dexter–SW Lake Union site (2009–2013). Season n Min. Max. Median Mean Summer 29 11.6 23.9 16.8 17.3 Fall 22 12.1 37.6 17.5 19.1 Winter 20 17.0 33.9 24.0 24.4 Spring 30 10.8 36.6 22.5 22.7 All year 101 10.8 37.6 20.6 20.7

3.7.4 Phytoplankton Community and Biovolume Appendix G documents an analysis of King County monitoring data on phytoplankton community composition and biovolume. In general, the findings are as follows:  The most common phytoplankton families in Lake Union/Ship Canal are bacillariophyta (diatoms), cryptophyta, chlorophyta (green algae), cyanobacteria (blue‐green algae), and chrysophyta. Dinoflaggellates and euglena are seldom found.  Species richness is greatest in the summer, with cyanobacteria representing between 10 and 90 percent on a cell count basis but less than 3 percent by biovolume.  Peaks in biovolume are typically seen in March/April and August/September.  By biovolume, diatoms are the dominant family, especially Tabellaria spp., Stephanodiscus spp., Fragilaria spp., and Melosira spp. Diatoms comprise the majority of cell counts throughout the year, excluding late summer when they are sub‐dominant to cyanobacteria and sometimes chlorophytes. Cryptophytes (especially Cryptomonas spp.) are typically sub‐dominant throughout the year, excluding late summer when cyanobacteria and chlorophytes are more numerous.

3.8 Metals

Water column metals have not been part of King County’s routine freshwater monitoring program. Metals data collection in Lake Union/Ship Canal has been discontinuous, and long‐term trend analysis is not possible.

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3.8.1 Methodology The most recent metals data (quarterly samples from 2000 through 2008) at the five King County monitoring sites were used to describe current conditions. Metals data from samples collected prior to 2000 were not used because improvements in precision and accuracy of laboratory methods since 2000 have rendered early metals data largely obsolete.

KCEL analyzes the dissolved (< 0.45 microns) and total fractions of metals in the water column using ICP‐MS (EPA1640). Prior to 2001, Frontier Geosciences of Seattle analyzed total and dissolved mercury using cold vapor atomic fluorescence spectrometry (EPA1631[E]). A conservative approach was used for analyzing data; if samples were analyzed past their hold times, the data were not used. A sample was qualified with “B” if blank contamination was detected in analytical method blanks and the sample concentration was less than five times the concentration of the sample blank; these samples were not used for data analysis. Chromium, nickel, and zinc were occasionally detected in analytical method blanks; dissolved zinc was the most common laboratory contaminant.

Metals tested included dissolved and total arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, and zinc. Mean values of analytes with the presence of non‐detects were calculated using the Kaplan‐Meier estimator. Metals concentrations were compared between sites and depths using the Peto & Peto modification of the Gehan‐ Wilcoxon test for metals with the presence of non‐detects and nonparametric Mann‐ Whitney tests for metals without non‐detects. Appendix D presents summary statistics for all dissolved and total metals.

To determine concentrations of metals in the salt water entering Salmon Bay through the Locks, data were investigated from a site (“Shilshole”) located at Shilshole Bay and the mouth of Salmon Bay downstream from the Locks (249160 Northing, 1253227 Easting).

3.8.2 Current Conditions

Total Metals From 2000 through 2008, total arsenic, chromium, copper, lead, mercury, nickel, and zinc were consistently detected at all monitoring sites. Cadmium and selenium were seldom detected (five detects of cadmium and one detect of selenium). Silver was never detected above the MDL in the ambient water.

Total metals concentrations were typically greater in the hypolimnion than in the epilimnion; significant differences were found for arsenic, copper, lead, nickel, zinc at the Dexter–SW Lake Union site. There were greater concentrations of copper in the epilimnion than the hypolimnion. This anomaly may be due to three factors:  Uptake of copper in phytoplankton as a micronutrient

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 Ready release of copper into a soluble phase during the conversion to fecal material and the decomposition of phytoplankton, whose concentrations are higher near the surface than at depth (Reynolds and Hamilton‐Taylor, 1992)  Presence of copper‐based antifouling boat hull paint (Srinivasan and Swain, 2007) The spatial distribution of most metals in the epilimnion shows that concentrations are generally greatest near the Locks and decrease moving upstream (Figure 3‐36). Concentrations of arsenic, copper, lead, nickel, and zinc are significantly higher at the Locks–Salmon Bay site than all other sites except the NE‐Lake Union–Portage Bay site.

Dissolved Metals Dissolved arsenic, chromium, copper, mercury, nickel, and zinc were consistently detected at all monitoring sites. Lead was occasionally detected, most commonly near the Locks. Selenium was seldom detected (three detections in the hypolimnion at Dexter–SW Lake Union). Cadmium and silver were never detected above the MDL in the ambient water.

Dissolved metals concentrations were typically greater in the hypolimnion than in the epilimnion; significant differences were found for copper, lead, nickel, and zinc at the Dexter–SW Lake Union site. Similar to total copper, concentrations of dissolved copper were greater in the epilimnion than the hypolimnion.

The spatial distribution of most metals in the epilimnion shows that concentrations are generally greatest at the Locks–Salmon Bay site and decrease moving upstream (Figure 3‐37). Concentrations of arsenic, copper, lead, nickel, and zinc were significantly higher at the Locks site than at all other sites, except for copper at Dexter–SW Lake Union, but copper concentrations near the Locks were still greater than those at Dexter. Water hardness was also greatest near the Locks. Chromium and mercury concentrations were not statistically distinguishable between the five monitoring sites.

Effects of Salt Water on Metals Concentrations The salt water entering from Shilshole Bay may be a source of certain dissolved metals, such as cadmium and vanadium, to Salmon Bay. However, for the majority of metals, the concentrations in Shilshole Bay are lower than those in Salmon Bay. Additionally, it does not appear that the intruding salt water is likely to be the predominant source of elevated metal concentrations found in the saltwater layer in the Lake Union basin. Metals concentrations at the Shilshole site are typically lower than those in the saltwater layer at the Dexter–SW Lake Union site. (See Appendix H for further discussion on the potential effects of saltwater intrusion on Lake Union’s metal concentrations.)

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Chromium Arsenic

Lead Copper

Nickel Mercury

Zinc

Figure 3-36. Distribution of total metals in the epilimnion of Lake Union/Ship Canal and Shilshole Bay (2000–2008). Black solid line represents maximum method detection limit. Note log-scale.

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Arsenic Chromium

Copper Mercury

Nickel Zinc

Figure 3-37. Distribution of dissolved metals in the epilimnion in Lake Union/Ship Canal and Shilshole Bay 2000–2008). Solid black line repesents maximum method dectection limit. Note log-scale.

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3.8.3 Comparison to Criteria Washington State has promulgated acute and chronic water quality criteria for 10 of the 15 metals analyzed (WAC 173‐201A‐240). In addition, EPA has established recommended Human Health Criteria for 9 metals. King County has measured all 9 metals in Lake Union/Ship Canal, although the inorganic fraction of arsenic has not been measured. The EPA criteria for the consumption of organisms are aimed to prevent adverse effects on humans and are based on body weight, fish consumption rate, bioaccumulation factors, health toxicity values, and relative source contributions.

The Washington State criteria for cadmium, chromium‐III, copper, lead, nickel, silver, and zinc are calculated based on water hardness. To compare metals concentrations to the criteria, criteria values were calculated using the hardness value for the corresponding metal sample; the hardness values ranged from 34.3 mg CaCO3/L to 795 mg CaCO3/L. The higher hardness values were associated with saltwater intrusions. The median and 90th percentile for hardness values were 39.2 mg/L and 50.4 mg/L, respectively. The range of criteria values is presented in Appendix C.

Dissolved metals concentrations were compared to the criteria for most metals, (Table 3‐30). The exceptions are the acute and chronic criteria for chromium and the chronic criterion for mercury; these criteria are based on the total amount present rather than the dissolved fraction. The available data indicate that overall metals concentrations are low in the study area. At no point did the ambient water in Lake Union/Ship Canal exceed the hardness‐adjusted state criteria or the EPA Human Health Criteria.

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Table 3-30. Detection frequency and maximum of metals concentrations (µg/L) in Lake Union/Ship Canal compared to Washington State and EPA water quality criteria. EPA Human WA State Aquatic Life Highest Max. Min. Max. Health Criteria for Criteria Analyte FOD Site/Depth Detect MDL MDL Consumption of Mean Acute Chronic Organism Only Antimony, dissolved 158/187 0.197 0.15 0.2 0.5 640 — — Arsenic, dissolved 185/185 8.69 1.43 NA NA — 360 190 Arsenic, inorganic 0.14a — — Barium, dissolved 174/174 39.4 6.85 NA NA — — — Beryllium, dissolved 0/187 NA < MDL 0.01 0.2 — — — Cadmium, dissolved 0/187 NA < MDL 0.01 0.2 — 1.27c 0.5c Chromium (III) — 245c 83.9c Chromium (VI) — 15 10 Chromium, total 167/185 2.8 0.26 0.4 0.4 — — — Copper, dissolved 176/176 5.69b 2.87 NA NA — 6.74c 4.9c Cyanide (non-metal) 400 — — Lead, dissolved 33/187 0.74 0.0554 0.025 0.2 — 21.81c 0.85c Manganese, 1/12 2.6 < MDL 2 2 100 — — dissolved Mercury, dissolved 109/137 0.00135 0.000437 0.2 0.2 — 2.1 Mercury, total 156/177 0.00503 0.000993 0.0002 0.2 — — 0.012 Nickel, dissolved 187/187 2.6 0.609 NA NA 4,600 616c 68.4c Selenium, dissolved 3/187 1.1 0.616 0.5 25 4,200 20 5 Silver, dissolved 0/184 NA < MDL 0.01 0.5 — 0.64c — Thallium, dissolved 6/176 0.018 < MDL 0.01 0.2 0.47 — — Zinc, dissolved 136/141 15 4.32 0.5 0.5 26,000 49.8c 45.4c FOD = frequency of detection; MDL = method detection limit. a. This criterion is based on carcinogenicity of 10‐6 risk. Alternative risk levels may be obtained by moving the decimal point (for example, for a risk level of 10‐5, the decimal point would be moved one place to the right). b. Maximum concentration of dissolved concentration associated with saltwater intrusion in Lake Union and high hardness. Copper concentration did not exceed hardness‐based criterion. c. Hardness‐based calculation using median hardness value of 39.2 mg CaCO3/L; see WAC 173‐201A‐240 for equations.

King County 3–67 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

3.9 Organic Chemicals

Similar to metals, water column organic chemicals (organics) are not part of King County’s routine monitoring program in Lake Union/Ship Canal. Organics data were measured sporadically, and long‐term trend analysis is not possible.

The largest issues associated with assessing available organics data are the detection limits for most parameters and the abundance of blank contamination. Analytical methods have substantially improved over the past decade and many detection limits have decreased. Furthermore, KCEL has decreased the amount of phthalates in the laboratory to reduce the occurrence of blank contamination. With decreased detection limits and consistent sampling, statistical comparisons could be made between sites that may reveal spatial patterns in the distribution of organic compounds in future studies.

Limited evidence suggests that a substantial saltwater intrusion can indirectly cause elevated PAH and carbazole concentrations in the hypolimnion through prolonged hypolimnetic isolation. The effect of decreased pH and DO and increased conductivity on the bioavailability of organic compounds is not known. See Appendix H for a discussion of the potential effects of saltwater intrusion.

Quarterly data from 2000 through 2004 were used to assess current conditions from the Locks–Salmon Bay (0512), Dexter–SW Lake Union (A522), and Montlake Cut (0540) sites. Data from April and May 2000 were used to assess current conditions from the Fremont– NW Lake Union (0518) site and from sites 0527, 0535, A535, B535, and C535. Figure 3‐38 shows sampling sites. Site 0527 is located in north Lake Union, south of Gas Works Park, and sites 0535, A535, B535, and C535 are located in Lake Union’s northeast arm near the outfall from the Densmore drainage basin. Organics data from samples collected prior to 2000 were not used because improvements in the precision and accuracy of laboratory methods since 2000 have made earlier organics data largely obsolete.

3.9.1 Current Conditions The analysis included 127 organic chemicals and total oil and grease at varying frequencies and time periods. (See Appendix D for a list of compounds and their MDLs, frequency of detection, and additional summary statistics.) In addition, endocrine disrupting compounds (EDCs) were measured in 2003. Of all 127 organics, 24 were detected in Lake Union/Ship Canal. Mean values of analytes with the presence of non‐detects were calculated using the Kaplan‐Meier estimator. When possible, organics concentrations were compared between sites and depths using the Peto & Peto modification of the Gehan‐Wilcoxon test for analytes with the presence of non‐detects and the nonparametric Mann‐Whitney tests for analytes without non‐detects.

King County 3–68 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 3-38. Sampling locations for organic chemicals in Lake Union/Ship Canal (2000–2004).

Table 3‐31 presents the number of organics detected at each site, the number tested for, and the frequency of detection for the 24 that were detected in Lake Union/Ship Canal. The hypolimnion at Dexter–SW Lake Union had the greatest relative frequency of detections followed by the Locks–Salmon Bay and Montlake Cut sites. (The limited sampling at the Fremont–SW Lake Union site and the four Densmore drainage sites in the northeast arm of Lake Union does not allow for a meaningful comparison.) The detections suggest that organic compounds are introduced to Lake Union/Ship Canal through stormwater and CSO outfalls, weathering of in‐lake structures, resuspension of sediment, and inflow from Lake Washington.

The ability to conduct spatial analysis of organic compounds was limited because of the low level of detections. Sufficient data, however, were available to compare the epilimnetic concentrations of caffeine and dimethyl phthalate at the Locks–Salmon Bay, Dexter–SW Lake Union, and Montlake Cut sites. Concentrations of these two parameters were significantly greater at the Locks and Dexter sites than at Montlake (Appendix C).

King County 3–69 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table 3-31. Number and frequency of detections for the 24 organic chemicals detected in Lake Union/Ship Canal (2000–2004). Number of Percent Site Depth Organics FOD Detection Detected Locks–Salmon Bay (0512) Epilimnion 10 92/592 15.5 Fremont–NW Lake Union (0518) Epilimnion 6 10/41 24.4 Epilimnion 18 43/239 18.0 Dexter–SW Lake Union (A522) Hypolimnion 15 67/263 25.5 0527 Epilimnion 2 6/84 7.1 0535 Epilimnion 2 3/42 7.1 A535 Epilimnion 2 4/42 9.5 B535 Epilimnion 2 4/42 9.5 C535 Epilimnion 2 4/42 9.5 Montlake Cut (0540) Epilimnion 12 51/517 9.9

FOD = frequency of detection.

PAHs Table 3‐32 presents the frequency of detection for each sampling event where at least one PAH was detected, number of PAHs detected, and the maximum sum of detected PAHs. While PAHs were detected more commonly in the Locks–Salmon Bay site, a greater variety of PAHs was detected at the Dexter–SW Lake Union site. Only pyrene was detected more frequently at the Locks than at Dexter (Appendix D).

Table 3-32. Number and frequency of PAH detections and maximum detected and potential concentrations (µg/L) of total PAHs (ΣPAHs) in Lake Union/Ship Canal (2000–2004). Unique Max. Detected Percent PAHs ΣPAH Site Depth FOD Detection Detected Concentration Locks–Salmon Bay Epilimnion 12/15 80.0 3 0.08 (0512) Fremont–NW Lake Epilimnion 1/1 100 2 0.02 Union (0518) Dexter–SW Lake Epilimnion 4/13 30.8 9 2.38 Union (A522) Hypolimnion 4/12 33.3 9 5.14 0527 Epilimnion 0/1 0 0 0 0535 Epilimnion 0/1 0 0 0 A535 Epilimnion 0/1 0 0 0 B535 Epilimnion 0/1 0 0 0 C535 Epilimnion 0/1 0 0 0 Montlake Cut Epilimnion 6/13 46.2 4 0.18 (0540) FOD = frequency of detection..

King County 3–70 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Concentrations of PAHs were typically greatest in the hypolimnion at the Dexter–SW Lake Union site, but data are insufficient for statistical comparison between sites. The detection of PAHs in the hypolimnion suggests potential resuspension from the sediments, especially since these detections occurred only during periods of thermal or saline stratification. The greatest concentration in PAHs in the epilimnion at Dexter occurred at the end of September 2000. On this sampling date, the concentration of PAHs in the hypolimnion was less than that of the epilimnion, which is atypical. The deterioration of thermocline may have released resuspended PAHs from the hypolimnion into the epilimnion.

The detection of PAHs in the epilimnion at the Locks–Salmon Bay, Dexter–SW Lake Union, and Montlake Cut sites when whole‐lake mixing had not recently occurred indicates potential external loading from stormwater runoff, CSOs, or the weathering of creosote‐ treated wood pilings.

PCBs and PBDEs From 2000 through 2004, PCBs were not detected and PBDEs were not measured in Lake Union/Ship Canal. In April, June, August, October, and December 2011 and February 2012, sampling and analysis of PCB and PBDE congeners with low detection limits were completed at the Montlake Cut site and at a site in Salmon Bay approximately 200 m upstream of the Locks. Composites taken from 1 m below the surface, the mid‐water column, and 1 m above the bottom were analyzed. The results of this survey are presented in Table 3‐33. Total PCBs and PBDEs were detected at each site for each sampling date. Concentrations of total PCBs and total PBDEs were higher at the Salmon Bay site than at Montlake.

Table 3-33. Total PCB and PBDE concentrations (pg/L) from the 2011–2012 high-resolution survey of two sites in Lake Union/Ship Canal. Site FOD Min. Max. Mean Median Salmon Bay 6/6 138 583 295 201 Total PCBs Montlake Cut 6/6 51 258 108 85 Salmon Bay 6/6 29 2148 801 603 Total PBDEs Montlake Cut 6/6 179 1617 647 530 FOD = frequency of detection; pg = 10‐6 µg.

3.9.2 Comparison to Criteria Table 3‐34 presents the frequency of detection, maximum detection, maximum mean concentration at sampling site and depth, MDL range, and water quality criteria (where applicable) for organic chemicals. Washington State has adopted EPA’s recommended national water quality criteria for human health for 85 chemical pollutants under the National Toxics Rule (40 CFR 131.36). The state has established water quality criteria for the protection of aquatic life for 13 organics.

King County 3–71 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Findings from the 2000−2004 organics monitoring and the 2011−2012 PCB/PBDE congener monitoring are as follows:  From 2000 through 2004, no organic compounds were detected at levels above the state aquatic life criteria. The detection limit, however, was greater than the state chronic criteria for aldrin, dieldrin, chlordane, alpha‐chlordane, trans‐chlordane, DDT and its metabolites, endrin, heptachlor, parathion‐ethyl and parathion‐methyl, toxaphene, and total Aroclors (PCBs).  Congener analysis in 2011−2012 detected PCBs at levels below the state criteria for aquatic life but above the EPA recommended Human Health Criteria. There are no criteria for PBDEs.  Bis(2‐ethylhexyl)phthalate, pentachlorophenol, benzo(b)fluoranthene, and total PCBs (congeners) exceeded the EPA Human Health Criteria in at least one sample. PCBs were above the criteria in nearly every sample, except for one sample from the Montlake Cut. The concentrations of bis(2‐ethylhexyl)phthalate in Lake Union/Ship Canal are difficult to estimate because of the presence of blank contamination in much of the analyses, which can create elevated detection limits. The available data are insufficient to indicate the frequency exceedances of the Human Health Criteria for bis(2‐ethylhexyl)phthalate.  Detection limits for several organic compounds were above the associated Human Health Criteria. These compounds are as follows: aldrin, chlordane, DDT and its metabolites, dieldrin, heptachlor, heptachlor epoxide, toxaphene, benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, dibenzo(a,h)anthracene, chrysene, indeno(1,2,3‐Cd)pyrene, total Aroclors (PCBs), benzidine, hexachlorobenzene, and pentachlorophenol.

King County 3–72 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table 3-34. Detection frequency and maximum concentrations (µg/L) of organic chemcials in Lake Union/Ship Canal compared to water quality criteria (2000–2004). Highest mean for a monitoring station is also provided. Exceedances of EPA Human Health Criteria are highlighted in red and of Washington State criteria in bold. Method detection limits above the state chronic criteria are in bold; limits above Human Health Criteria are highlighted in yellow. Highest EPA Human Health WA State Aquatic Life Max. Site/ Min. Max. Criteria for Criteria Analyte FOD Detection Depth MDL MDL Consumption of Acute Chronic Mean Organism Only Chlorinated Herbicides and Pesticides 2,4-D 10/83 0.2 0.096 0.03 0.11 2,4-DB 0/83 NA < MDL 0.043 0.13 2,4,5-T 0/83 NA < MDL 0.048 0.096 2,4,5-TP (silvex) 0/83 NA < MDL 0.016 0.16 4,4'-DDD 0/104 NA < MDL 0.0047 0.0053 0.00084b 1.1 0.001 4,4'-DDE 0/104 NA < MDL 0.0047 0.0053 0.00059b 1.1 0.001 4,4'-DDT 0/104 NA < MDL 0.0047 0.0053 0.00059b 1.1 0.001 Aldrin 0/104 NA < MDL 0.0047 0.0053 0.00014 b 2.5 0.0019 Alpha-BHC 0/104 NA < MDL 0.0047 0.0053 0.013 b Alpha-chlordane 0/10 NA < MDL 0.0047 0.0049 2.4 0.0043 Beta-BHC 0/104 NA < MDL 0.0047 0.0053 0.046 a Chlordane 0/94 NA < MDL 0.024 0.026 0.00059 2.4 0.0043 Dalapon 0/83 NA < MDL 0.012 0.17 Delta-BHC 0/104 NA < MDL 0.0047 0.0053 Dicamba 0/83 NA < MDL 0.022 0.17 Dichloroprop 0/83 NA < MDL 0.011 0.14 Dieldrin 0/104 NA < MDL 0.0047 0.0053 0.00014b 2.5 0.0019 Dinoseb 0/83 NA < MDL 0.029 0.076 Endosulfan I 0/104 NA < MDL 0.0047 0.0053 2. 0.22 0.056 Endosulfan II 0/104 NA < MDL 0.0047 0.0053 2. 0.22 0.056 Endosulfan sulfate 0/104 NA < MDL 0.0047 0.0053 2. Endrin aldehyde 0/104 NA < MDL 0.0047 0.0053 0.81

King County 3–73 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Highest EPA Human Health WA State Aquatic Life Max. Site/ Min. Max. Criteria for Criteria Analyte FOD Detection Depth MDL MDL Consumption of Acute Chronic Mean Organism Only Endrin 0/104 NA < MDL 0.0047 0.0053 0.81 0.18 0.0023 Gamma-BHC (lindane) 0/104 NA < MDL 0.0047 0.0053 0.063 2. 0.08 Heptachlor 0/104 NA < MDL 0.0047 0.0053 0.00021b 0.52 0.0038 Heptachlor epoxide 0/104 NA < MDL 0.0047 0.0053 0.00011b 0.52 0.0038 Hexachlorocyclopentadiene 0/12 NA < MDL 0.24 0.24 17,000b MCPA 0/83 NA < MDL 0.011 0.23 MCPP 0/83 NA < MDL 0.013 0.13 Methoxychlor 0/104 NA < MDL 0.024 0.026 Toxaphene 0/104 NA < MDL 0.047 0.053 0.00075a 0.73 0.0002 Trans-chlordane 0/10 NA < MDL 0.0047 0.0049 2.4 0.0043 Organophosphate Pesticides Chlorpyrifos 0/83 NA < MDL 0.032 0.036 0.083 0.041 Diazinon 0/83 NA < MDL 0.041 0.045 Disulfoton 0/83 NA < MDL 0.025 0.028 Malathion 0/83 NA < MDL 0.045 0.051 Parathion-ethyl 0/83 NA < MDL 0.042 0.047 0.065 0.013 Parathion-methyl 0/83 NA < MDL 0.034 0.038 0.065 0.013 Phorate 0/83 NA < MDL 0.031 0.035 Endocrine Disrupting Compounds Atrazine 0/10 NA < MDL 0.047 0.049 Bis(2-ethylhexyl)adipatea 0/19 NA

King County 3–74 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Highest EPA Human Health WA State Aquatic Life Max. Site/ Min. Max. Criteria for Criteria Analyte FOD Detection Depth MDL MDL Consumption of Acute Chronic Mean Organism Only Progesterone 0/19 NA < MDL 0.0094 0.0097 Testosterone 0/19 NA < MDL 0.0094 0.0097 Total 4-nonylphenol* 1/19 0.05 < MDL 0.047 0.097 Vinclozolin 0/19 NA < MDL 0.0094 0.0097 Low Molecular Weight Polycyclic Aromatic Hydrocarbons 2-chloronaphthalene 0/101 NA < MDL 0.0047 0.15 2-methylnaphthalene 5/101 0.715 0.279 0.047 0.39 Acenaphthene 5/101 0.824 0.234 0.0047 0.097 Acenaphthylene 4/101 0.022 < MDL 0.0047 0.15 Anthracene 4/101 0.044 0.0164 0.0047 0.15 110,000 Fluorene 5/101 0.428 0.136 0.0047 0.15 14,000 Naphthalene 18/101 2.63 0.816 0.012 0.39 Phenanthrenea 9/101 0.404 0.149 0.0047 0.15 High Molecular Weight Polycyclic Aromatic Hydrocarbons Benzo(a)anthracene 0/101 NA < MDL 0.012 0.15 0.03b Benzo(a)pyrene 0/101 NA < MDL 0.0047 0.24 0.031b Benzo(b)fluoranthene 1/101 0.0471 < MDL 0.0047 0.39 0.031b Benzo(g,h,i)perylene 0/95 NA < MDL 0.024 0.24 Benzo(k)fluoranthene 0/101 NA < MDL 0.0047 0.39 0.031b Dibenzo(a,h)anthracene 0/95 NA < MDL 0.024 0.39 0.031b Chrysene 0/101 NA < MDL 0.012 0.15 0.031a Fluoranthene 19/101 0.0405 0.0218 0.0047 0.15 370. Indeno(1,2,3-Cd)pyrene 0/101 NA < MDL 0.024 0.24 0.031b Pyrene 29/101 0.194 0.0113 0.0047 0.15 11,000 PCBs Aroclor 1016 0/104 NA < MDL 0.047 0.053

King County 3–75 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Highest EPA Human Health WA State Aquatic Life Max. Site/ Min. Max. Criteria for Criteria Analyte FOD Detection Depth MDL MDL Consumption of Acute Chronic Mean Organism Only Aroclor 1221 0/104 NA < MDL 0.047 0.053 Aroclor 1232 0/104 NA < MDL 0.047 0.053 Aroclor 1242 0/104 NA < MDL 0.047 0.053 Aroclor 1248 0/104 NA < MDL 0.047 0.053 Aroclor 1254 0/104 NA < MDL 0.047 0.053 Aroclor 1260 0/104 NA < MDL 0.047 0.053 Total Aroclors 0/104 NA < MDL 0.047 0.053 0.00017b 2. 0.014 Total PCBs (pg) 12/12 583 295 170b 2*106 14,000 Semivolatile Organic Compounds (SVOCs) 1,2-dichlorobenzene 0/101 NA < MDL 0.024 0.15 17,000 1,2,4-trichlorobenzene 0/91 NA < MDL 0.0047 0.15 1,3-dichlorobenzene 0/101 NA < MDL 0.024 0.15 2,600 1,4-dichlorobenzene 0/101 NA < MDL 0.024 0.15 2,600 2-chlorophenol 0/91 NA < MDL 0.047 0.49 2-methylphenol 0/91 NA < MDL 0.12 0.25 2-nitroaniline 0/91 NA < MDL 0.047 0.97 2-nitrophenola 2/91 0.031 < MDL 0.024 0.253 2,4-dichlorophenol 0/101 NA < MDL 0.047 0.49 790b 2,4-dimethylphenol 0/91 NA < MDL 0.24 1.5 2,4-dinitrophenol 0/91 NA < MDL 0.47 1 14,000 2,4-dinitrotoluene 0/91 NA < MDL 0.024 0.097 9.1a 2,4,5-trichlorophenol 0/91 NA < MDL 0.059 0.97 2,4,6-trichlorophenol 0/101 NA < MDL 0.024 0.97 6.5b 2,6-dinitrotoluene 0/91 NA < MDL 0.024 0.097 3-nitroaniline 0/91 NA < MDL 0.24 0.97 3,3'-dichlorobenzidine 0/91 NA < MDL 0.24 0.75

King County 3–76 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Highest EPA Human Health WA State Aquatic Life Max. Site/ Min. Max. Criteria for Criteria Analyte FOD Detection Depth MDL MDL Consumption of Acute Chronic Mean Organism Only 4-bromophenyl phenyl 0/91 NA < MDL 0.012 0.097 ether 4-chloro-3-methylphenol 0/91 NA < MDL 0.12 0.49 4-chloroaniline 0/91 NA < MDL 0.12 0.49 4-chlorophenyl phenyl 0/91 NA < MDL 0.012 0.15 ether 4-methylphenol 0/91 NA < MDL 0.12 0.25 4-nitroaniline 0/91 NA < MDL 0.24 0.97 4-nitrophenol 0/91 NA < MDL 0.24 0.5 4,6-dinitro-o-cresol 0/91 NA < MDL 0.47 1 Aniline 0/12 NA < MDL 0.47 0.49 Benzidine 0/12 NA < MDL 5.7 5.8 0.00054b Benzoic acid 0/12 NA < MDL 0.94 0.97 Benzyl alcohol 0/12 NA < MDL 0.24 0.24 Benzyl butyl phthalate* 0/101 NA < MDL 0.012 0.15 Bis(2- 0/91 NA < MDL 0.0047 0.24 chloroethoxy)methane Bis(2-chloroethyl)ether 0/91 NA < MDL 0.0047 0.15 1.4b Bis(2-chloroisopropyl)ether 0/91 NA < MDL 0.0047 0.49 170,000 Bis(2-ethylhexyl)phthalatea 23/95 148 15.3 0.0844 3.79 5.9b 77/10 Caffeinea 0.179 0.0714 0.0048 0.049 1 Carbazole 5/101 0.206 0.0613 0.012 0.24 Coprostanol 0/12 NA < MDL 2.4 2.4 10/10 Di-n-butyl phthalatea 0.4 < MDL 0.0286 0.24 12,000 1 Di-n-octyl phthalate 2/91 0.048 < MDL 0.0047 0.15 Dibenzofuran 5/101 0.515 0.144 0.0047 0.24 Diethyl phthalatea 3/101 0.209 < MDL 0.0137 0.24 120,000

King County 3–77 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Highest EPA Human Health WA State Aquatic Life Max. Site/ Min. Max. Criteria for Criteria Analyte FOD Detection Depth MDL MDL Consumption of Acute Chronic Mean Organism Only Dimethyl phthalatea 45/91 0.0511 0.0144 0.0047 0.097 2,900,000 Hexachlorobenzene 0/95 NA < MDL 0.012 0.15 0.00077b Hexachlorobutadiene 0/91 NA < MDL 0.024 0.24 50b Hexachloroethane 0/85 NA < MDL 0.012 0.24 8.9b Isophorone 1/91 0.0177 < MDL 0.0047 0.24 600b N-nitrosodi-n-propylamine 0/91 NA < MDL 0.047 0.24 N-nitrosodimethylamine 0/78 NA < MDL 0.012 0.97 8.1b N-nitrosodiphenylamine 0/91 NA < MDL 0.12 0.25 16b Nitrobenzene 0/91 NA < MDL 0.0047 0.24 1,900b Pentachlorophenol 2/101 0.23 < MDL 0.059 0.94 8.2b 3.32 2.1 Phenola 0/101 NA

FOD = frequency of detection; MDL = method detection limit. a Blank contamination present in a least one sample. EPA National Functional Guidelines were followed (EPA, 2014b). b This criterion is based on carcinogenicity of 10‐6 risk. Alternative risk levels may be obtained by moving the decimal point (for example, for a risk level of 10‐5, the decimal point would be moved one place to the right).

King County 3–78 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

4.0 SEDIMENT QUALITY Sediments can provide a historical record of pollution in a waterbody. While pollution discharged into surface waters may quickly become diluted, many chemical pollutants settle to the bottom and bind to bottom sediments. The chemicals that accumulate in sediments may adversely affect benthic organisms that have direct contact with the sediments and humans through consumption of fish and shellfish.

This chapter discusses data from sediment studies conducted from 1981 through 2014 to characterize conditions in the sediment of the different areas of Lake Union/Ship Canal. These sediment studies were performed by a number of agencies and private entities for a variety of purposes. The chapter focuses on sediment in the biologically active zone (top 0– 10 cm).Results of benthic invertebrate sampling are also discussed. Appendix E presents sediment data in greater detail.

A major limitation in the analysis of current sediment quality in Lake Union/Ship Canal is the lack of a recent system‐wide dataset that examines the full suite of chemicals listed under Washington State’s freshwater Sediment Management Standards. The most recent waterbody‐wide dataset was produced in 2001 by King County. More recent studies focused on select areas.

4.1 Mechanics of Sediment Contamination

The concentration of contaminants in freshwater surface sediments is largely the result of four processes: (1) accumulations of sediments that originate from the water column and settle on the bottom, (2) mixing of sediments from below via bioturbation and propwash, (3) diffusive and degradation processes in the sediment, and (4) burial of older sediments by newly settled sediments over time (Figure 4‐1).  Water column sediments that settle to the bottom are derived from nearby particulate sources in the water and removed from the surface sediments by burial.  Mixing in the surface sediments can occur from the physical activities of benthic organisms and from propwash and ship scour in shipping waterways. Propwash and ship scour may also resuspend and transport sediments.  Biodegradation and diffusive losses across the sediment‐water interface may be formulated as a combined first‐order loss term.

Current pathways of sediment contaminants in Lake Union/Ship Canal include stormwater and CSO outfalls, atmospheric deposition, and groundwater. Sources include commercial and recreational boaters, contaminated sediments at the retired coal gasification plant (Gas Works), creosote‐treated wood pilings, and other industries and businesses around the lake (GLWTC, 2001). Gas Works is the most notable historical source of contaminants. Six outlets discharged wastes from the plant into Lake Union, including cooling water from the oil spray of a gas machine and blowdown from steam boilers that contained chemicals used

King County 4‐1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

to soften and treat the water. Several of these outlets allowed oily wastewater to reach Lake Union (Foster, 1943).

FRESHWATER

Figure 4-1. Schematic of processes controlling chemical concentrations in surface sediments in fresh water (source: Jacobs et al., 1988).

4.2 Sediment Porewater Salinity

In September and October 1999, an Ecology study investigated sediment porewater salinity in Salmon Bay and northwest Lake Union (Rogowksi, 2000) to understand the effects of the intrusion of salt water from the Locks. Sediment pore water salinity values ranged from 0.16 ppt to 13 ppt. The study found a trend toward lower salinity levels moving east from the Locks. A little over half of the sediment samples collected showed salinity values that would classify them as low salinity sediment (between 0.5 ppt and 25 ppt). The authors noted that the salinity of sediments may have an impact on results of bioassays.

4.3 Sediment Management Standards

Sediment chemistry and toxicity data were compared to Sediment Cleanup Standards established under Washington State’s freshwater Sediment Management Standards (SMS) (Ecology, 2013) to identify sites of potential concern because of contaminated sediments. The freshwater SMS Sediment Cleanup Standards were developed to be protective of benthic organisms. The standards include both chemical and biological criteria.

King County 4‐2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Unlike for marine sediments, no numeric chemical and biological criteria have been established for freshwater sediments as Sediment Quality Standards (SQS) or Sediment Impact Zone maximum criteria (SIZMAX) (WAC 173‐204‐340). The SQS are used for addressing the release of hazardous substances from discharges permitted under NPDES that have the potential to contaminate sediment. The SIZMAX is used as an upper limit for chemical concentrations or biological effects within the immediate vicinity of a permitted discharge if a sediment impact zone has been authorized. A narrative benthic standard for freshwater sediment states that Ecology will address the sediment impacts resulting from the release of hazardous substances on a case‐by‐case basis using best professional judgment (WAC 173‐204‐340).

4.3.1 Chemical Criteria The freshwater SMS Sediment Cleanup Standards include two levels of chemical criteria (WAC 173‐204‐563):  The Sediment Cleanup Objective (SCO) is a “no adverse effects” level, meaning concentrations of chemicals in sediment below this level are expected to have no adverse effects on the benthic community. It is the level of biological effects permissible after completion of a cleanup action.  The Cleanup Screening Level (CSL) is the “minor adverse effects” level, which is used as an upper regulatory level for source control and cleanup decision making. Concentrations that fall between the SCO and CSL have an unknown effect on the benthic community. The chemical SCOs and CSLs are presented in Table 4‐1.

Table 4-1. Freshwater Chemical Sediment Cleanup Objectives (SCOs) and Cleanup Screening Levels (CSLs) (dry-weight basis). Chemical Parameter SCO CSL Conventional chemicals (mg/kg) Ammonia 230 300 Total sulfides 39 61 Metals (mg/kg) Arsenic 14 120 Cadmium 2.1 5.4 Chromium 72 88 Copper 400 1,200 Lead 360 ˃ 1,300 Mercury 0.66 0.8 Nickel 26 110 Selenium 11 ˃ 20 Silver 0.57 1.7 Zinc 3,200 ˃ 4,200 Organic Chemicals (µg/kg) 4-Methylphenol 260 2,000 Benzoic acid 2,900 3,800

King County 4‐3 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Chemical Parameter SCO CSL Beta-Hexachlorocyclohexane 7.2 11 Bis(2-ethylhexyl) phthalate 500 22,000 Carbazole 900 1100 Dibenzofuran 200 680 Dibutyltin 910 130,000 Dieldrin 4.9 9.3 Di-n-butyl phthalate 380 1,000 Di-n-octyl phthalate 39 ˃ 1,100 Endrin ketone 8.5 ˃ 8.5 Monobutyltin 540 ˃ 4,800 Pentachlorophenol 1,200 ˃ 1,200 Phenol 120 210 Tetrabutyltin 97 ˃ 97 Total PCB Aroclors 110 2,500 Total DDDs 310 860 Total DDEs 21 33 Total DDTs 100 8100 Total PAHs 17,000 30,000 Tributyltin 47 320 Bulk Petroleum Hydrocarbons (mg/kg) Total petroleum hydrocarbon (TPH) - diesel 340 510 Total petroleum hydrocarbon (TPH) - residual 3,600 4,400 A "˃" (greater than) before a CSL that the level is unknown but is above the concentration shown. If test results show concentrations above this CSL, bioassays should be conducted to evaluate potential benthic community toxicity. In this Lake Union/Ship Canal report, the minimum value provided in this table is treated as the CSL.

4.3.2 Biological Criteria Washington State has also established biological criteria under the Sediment Cleanup Standards for freshwater sediments based on toxicity to the benthic invertebrate community. Two species are used for freshwater bioassays: Chironomus tentans, a midge, and Hyalella azteca, an amphipod. To assess sediment quality using biological criteria, both species must be used and three endpoints, at least one chronic and at least one sublethal, must be considered. Additionally, appropriate control and reference sediment samples must meet performance standards. Similar to the chemical criteria, the biological criteria include SCOs and CSLs (Table 4‐2). The CSL biological criterion for a sampling station is exceeded when any two of the biological test results for a sampling station are above the SCO or one of the biological test results for a sampling station is above the CSL.

King County 4‐4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table 4-2. Freshwater Biological Sediment Cleanup Objectives (SCOs) and Cleanup Screening Levels (CSLs). Biological Performance Standard SCO for Each CSL for Each Test/Endpoint Control Reference Biological Test Biological Test

MT - MC ˃ 15% and MT - MC ˃ 25% and 10-day mortality MC ≤ 20% MR ≤ 25% MT vs MC SD MT vs MC SD (acute/ lethal) (p ≤ 0.05) (p ≤ 0.05)

MT - MC ˃ 10% and MT - MC ˃ 25% and 28-day mortality MC ≤ 20% MR ≤ 30% MT vs MC SD MT vs MC SD (chronic/ lethal) (p ≤ 0.05) (p ≤ 0.05) Hyalella azteca Hyalella azteca (MIGC - MIGT)/ 28-day growth (MIGC - MIGT)/ MIGC MIGC ≥ 0.15 MIGR ≥ 0.15 MIGC ˃ 0.25 and (chronic/ ˃ 0.40 and MIGT vs mg/individual mg/individual MIGT vs MIGC SD sublethal) MIGC SD (p ≤ 0.05) (p ≤ 0.05)

MT - MC ˃ 20% and MT - MC ˃ 30% and 10-day mortality MC ≤ 30% MR ≤ 30% MT vs MC SD MT vs MC SD (acute/lethal) (p ≤ 0.05) (p ≤ 0.05)

10-day growth (MIGC - MIGT)/ MIGC (MIGC - MIGT)/ MIGC MIGC ≥ 0.48 MIGR/MIGC ≥ (acute/ ˃ 0.20 and MIGT vs ˃ 0.30 and MIGT vs mg/individual 0.8 sublethal) MIGC SD (p ≤ 0.05) MIGC SD (p ≤ 0.05)

MT - MC ˃ 15% and MT - MC ˃ 25% and 20-day mortality MC ≤ 32% MR ≤ 35% MT vs MC SD MT vs MC SD (chronic/lethal) (p ≤ 0.05) (p ≤ 0.05) Chironomus tentans tentans Chironomus

(MIGC - MIGT)/ 20-day growth (MIGC - MIGT)/ MIGC MIGC ˃ 0.60 MIGR/MIGC ≥ MIGC ˃ 0.40 and (chronic/ ˃ 0.25 and MIGT vs mg/individual 0.8 MIGT vs MIGC SD sublethal) MIGC SD (p ≤ 0.05) (p ≤ 0.05)

C = control; MIG = mean individual growth at time final; SD = Statistically significant difference; R = reference; T = test.

4.4 Data Sources and Methodology

Data from a total of 40 studies in Lake Union/Ship Canal were reviewed; these studies include two recent King County sediment monitoring studies and multiple routine and compliance monitoring projects conducted by various agencies and private entities. The studies and projects included 405 geographically distinct sites in Lake Union/Ship Canal and 17 geographically distinct sites in Union Bay. Nineteen of the Lake Union/Ship Canal study area sites were eliminated from consideration in this analysis because they are located in an area that was dredged and capped after sampling, leaving 386 sites in the study for analysis.9 For sites that were sampled multiple times, the most recent sediment

9 In early 2014, sediments at the Northlake Shipyard west of Gas Works in northwest Lake Union were dredged and a 6‐inch cap of clean sand was placed over the area. The capping was completed on March 25,

King County 4‐5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal sample is presented. Data from these sites were compiled from Ecology’s Environmental Information Management (EIM) system database (http://www.ecy.wa.gov/eim/). Table 4‐3 gives information on the sediment studies compiled. Figures 4‐2 and 4‐3 show the locations and years for the sediment samples analyzed. Tables of data used for this analysis are available on request.

For this analysis, no effort was made to distinguish sampling methods. Although most sediment data are collected for regulatory purposes with a van Veen grab sampler from 0– 10 cm, both core and van Veen grab samples were analyzed. The top stratum of core samples (typically 30 cm) was used. The following four core studies were not included in this analysis because the cores did not capture the top stratum of sediment or the surface core sample went beyond 50 cm into the sediment: Tri‐Star Marine (TRIMA90), Port of Seattle – Fishermen’s Terminal (POSFT04), South Lake Union Park (LKUNSO07), and Salmon Bay Marina (SALMO12).

Dry‐weight‐normalized sediment chemistry values and bioassay results were compared, where applicable, to the state’s freshwater Sediment Cleanup Standards based on protection of the benthic community (SCO and CSL). In Salmon Bay, sediment porewater salinity may exceed the threshold between “freshwater” and “low salinity” (WAC 173‐204‐ 200), particularly in late summer and early fall during high activity at the Locks (Rogowski, 2000). Because no sediment cleanup standards exist for low salinity sediment (WAC 173‐ 204‐562(5)), the concentrations in Salmon Bay sediments were compared to freshwater SCOs and CSLs. Further characterization of sediment salinity throughout the year in Salmon Bay, the Fremont Cut, and Lake Union is needed.

Because samples were collected over the course of over 30 years by a number of entities, analysis methods varied, different laboratories did the chemical analyses, parameters measured varied greatly between studies, and detection limits changed over time. Changes in detection limits may have resulted in non‐detects for some chemicals, particularly organic chemicals that occur at low concentrations:  Observations where a chemical was not detected and the detection limit was above either the SCO or CSL were not plotted for comparison to the standards because the true value is not known.  Observations where a chemical was not detected and the method limit was below the SCO were plotted because while the true value is unknown, the value is below the SMS.

Data rejected by the laboratory were removed from the dataset; data with possible blank contamination or hold‐time exceedances were included. Samples with blank contamination were handled according to EPA’s National Functional Guidelines (EPA, 2014b and c).

2014. Sediments sampled in this area before this date are not presented, and no post‐cleanup sediment values are in EIM.

King County 4‐6 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table 4-3. Studies with surface sediment samples taken in Lake Union/Ship Canal at undredged/uncapped locations found in Ecology’s Environmental Information Management (EIM) system database. No. of Study EIM ID Years Purpose Parameters Sites Published Report King County 1981– Conventionals, historical sediment LUUMON86 Routine sediment monitoring 14 Metro, 1993 1986 metals, organics samples Determine level and extent of EPA Lake Union sediment contamination caused by sediment EPAGAS84 1984 Metals, organics 30 Hileman et al., 1984 decommissioned gas plant at Gas investigationa Works Investigate the triad approach to Ecology – triad Conventionals, freshwater sediment assessment of approach – Gas GWPLKUNGWP 1985 metals, organics, 1 Yake et al., 1986 contaminated sediments near Gas Works bioassay, benthos Works used Evaluate sediment quality at Mallard SCLITE89/ Cove (Fairview Ave. E and E Metals, PCBs,b Seattle City Light 1989 11 Zisette, 1989 SCLTE89 Roanoke St.) and near the Lake PAHs Union Steam Plant Ecology – survey of Determine concentrations of Conventionals, contaminants in LKUNION 1990 chemical contaminants and toxicity metals, organics, 22 Cubbage, 1992 Lake Union of sediments in Lake Union area bioassay Metals, PAHs Kutzer Marine Park SLUPRK90 1990 2

Conventionals, Marco Shipyard MARCO90 1990 3 metals, organics PSDDA suitability characterization of maintenance dredged material for Conventionals, Tri-Star Marine TRIMA90 1990 0 USACE, 1990 potential placement at the Elliott Bay metals, organics open-water disposal site UNIMAR Drydock Metals, organics, UNIMAR 1991 6 (Yard 1) bioassays Metals, asbestos, FVO Marine Ways FVO92 1992 3 petroleum Monitor for NPDES permit Metals, organics, Lake Union Drydock LKUNDRDK 1992 4 Hart Crowser, 1992 requirements bioassays USACE recon study LWSCR92 1992 Metals 3 Pacific Marine NOAPMC94 1994 Metals, organics 6 NOAA, 1994 Center

King County 4‐7 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

No. of Study EIM ID Years Purpose Parameters Sites Published Report Conventionals, Investigate sediment contamination Seattle Commons SEACOM94 1994 metals, organics, 3 in south Lake Union bioassays EPA − Washington 1994– Investigate sediment contamination Natural Gas – EPAGAS95 Metals, organics 30 1995 near Gas Works Seattle Plant King County Sediment near Ballard, 11th Ave 1989– Conventionals, historical sediment KC_old NW, 3rd Ave W, Dexter Ave, and 5 Metro, 1993 1995 metals, organics samples Montlake CSO outfalls Monitor for NPDES permit Foss Maritime FOSS95 1995 Metals, organics 6 requirements King County Conventionals, historical sediment LUUMON95 1995 Routine sediment monitoring 10 metals, organics samples Site investigation report John Dunato Dunato Site ATC Environmental, DUNATO96 1996 and Company Dunato's Marine Metals, organics 4 Investigation Inc., 1996 Service and Supply Ecology – Salmon SALMII96/ Survey chemical contaminants in Serdar and Cubbage, 1995 Metals, organics 29 Bay Phase II SBAYPH2 Salmon Bay sediments 1996 Assess toxicity of sediments, delineate boundaries of highly Ecology – Salmon SALMIII97/ Metals, organics, 1997 contaminated areas, and confirm 27 Serdar et al., 2000 Bay Phase III SBAYPH3 bioassays sediment contamination found during Phase II study. King County – Assess sediment chemistry near University Regulator LUUCSO97 1997 stormwater outfall after CSO Metals, organics 14 Grothkopp, 1997 Post-Separation I separation Submitted to Ecology Monitor for NPDES permit Metals, organics, Tri-Star Marine TRI_STAR 1997 3 by Beak Consultants requirements bioassays 1996 Assess sediment chemistry near RETEC 1999 RETEC_99 1999 Metals, organics 36 Gas Works King County Assess sediment chemistry and Metals, organics, University Regulator LUUCSO00 2000 toxicity near stormwater outfall after 6 bioassays Post- Separation II combined sewer separation King County Lake Assess baseline sediment chemistry Metals, organics, LKWA00 2000 1 King County, 2004a Washington baseline and toxicity bioassays

King County 4‐8 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

No. of Study EIM ID Years Purpose Parameters Sites Published Report King County Lake Assess baseline sediment chemistry Metals, organics, King County, 2001 Union sediment FWLKUN01 2001 17 and toxicity bioassays King County, 2004a quality study Ecology − sediment Assess sediment toxicity near Gas Conventionals, toxicity near Gas RJAC005 2002 13 Ecology, 2003 Works boassays Works Assess sediment chemistry near Metals, organics, RETEC 2002 RETEC_02 2002 43 RETEC, 2002 Gas Works bioasssays Assess sediment chemistry near Metals, organics, TAMU 2002 TAMU_02 2002 13 Gas Works bioassays DMMP post-dredge anti-degradation Conventionals, Lakeside Industries LIPDS04 2004 1 USACE, 2005a evaluation metals, organics DMMP suitability characterization of Port of Seattle – Conventionals, 47,793 cubic yards of dredged Fishermen’s POSFT04 2004 metals, organics, 0 USACE, 2005b material for potential disposal at the Terminal bioassays Elliott Bay Lower Duwamish Assess sediment chemistry in urban Conventionals, River background LDWRRUN0 2005 waterbodies near Lower Duwamish dioxins/furans, 5 LDWG, 2010 surface sediment River PCBs, PCP Seaview stormwater Assess stormwater runoff from Conventionals, AJOH0049 2006 1 Ecology, 2006 outfall boatyard facilities. metals, organics Shannon & Wilson, South Lake Union Assess sediment quality of LKUNSO07 2007 Metals, organics 0 Inc., 2008 Park Waterways 3 and 4 USACE, 2010 Identify and characterize sandblast Ecology & Northlake Shipyard Northlake 2009 grit-impacted sediment in support of Metals 16 Environment Inc. and pre-cleanup Sediment09 planned removal action Herrera, 2009 King County 2007– Conventionals, KingLakeSeds Routine sediment monitoring 3 sediment monitoring 2010 metals, organics King County CSO Characterize sediment quality near Conventionals, KC_CSO_2011/ 2011– sediment quality CSO outfalls (3rd Ave W, University, metals (2013 24/11 King County, 2011a KC_CSO_2013 2013 characterization and Montlake) only), organics DMMP suitability characterization of 11,900 cubic yards of maintenance Conventionals, Salmon Bay Marina SALMO12 2012 dredged material for potential 0 USACE, 2012b. metals, organics placement at the Elliott Bay open- water disposal site.

King County 4‐9 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

No. of Study EIM ID Years Purpose Parameters Sites Published Report Remedial investigation for upland Jacobson Terminals JT_2014 2014 Metals, organics 5 Hart Crowser, 2014a soil. Northlake Shipyard Assessment of sediment before and FS23849623 2014 Metals, PAHs 0 Hart Crowser, 2014b pre- & post-dredging after dredging. EIM = Environmental Information Management System (Washington State Department of Ecology database). USACE = U.S. Army Corps of Engineers. NPDES = National Pollutant Discharge Elimination System. DMMP = USACE Dredged Material Management Program. PSDDA = Puget Sound Dredged Disposal Analysis. a It appears that through comparison with earlier data, incorrect values were entered into EIM for Site EPAGAS8414. These incorrect values were corrected based on the values in Metro (1993). b The values for PCB Aroclors for SCLITE89/SCLTE89 were not entered into EIM. Values from Metro (1993) were used.

King County 4‐10 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

. Figure 4-2. Location of sediment sampling sites and respective studies from Ecology’s Environmental Information Management system database. (See legend on following page.)

King County 4‐11 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Legend for Figure 4-2.

King County 4‐12 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 4-3. Location and year ranges of sediment sampling sites from Ecology’s Environmental Information Management system database.

King County 4‐13 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

The number of parameters measured depended on the goals of each sediment study. Numbers ranged from one parameter to 169 measurements of conventionals, metals, and organics in addition to bioassays. Ten sites did not measure any of the SMS contaminants. Only five studies (totaling 67 sites) performed a number of toxicity tests sufficient to meet SMS requirements, but control and reference requirements frequently were not met.

Data from six organic compounds, including all phenolic compounds, benzyl alcohol, and benzoic acid, are included in data tables. They are not shown on maps that compare sites with SMS and are not discussed below because of their ubiquity throughout Puget Sound, transitory nature, and natural sources and/or because of the lack of confidence in analytical precision and laboratory detection limits (Ecology, 2009; LDWG, 2011; LDWG 2013).

Control and reference samples for bioassay data were compared to the state’s performance standards to determine if a dataset was useable. Significant differences between control and sampled sediments were assessed using a one‐sided two‐sample permutation analysis using the “oneway_test” function from the “coin” package in R (Horthon et al., 2008).

4.5 Physical Structure of Sediments

The physical structure of freshwater sediments affects the distribution and concentration of metals and organic chemicals. For example, chemical concentrations are expected to be higher at sites with more fine particles that provide increased surface area for binding with chemicals. Sites with higher concentrations of total organic carbon (TOC) have a higher potential for binding with some organic compounds (Wenning et al., 2005).

The percentage of fine sediments (silt and clay) in Lake Union/Ship Canal is highly variable, ranging from less than 0.62 percent to 98.3 percent with a mean of 50.0 percent (n = 173). The distribution of particles appears to be influenced by the flow patterns in the system (Figure 4‐4). Fine sediments are transported through the narrow canals and fall out in the wide basins (Portage Bay, Lake Union, and Salmon Bay). Larger particles are dominant in narrow channels with higher flows and vessel traffic. The turbulence caused by the Locks may resuspend fine sediments in western Salmon Bay, but fine sediments tend to dominate along the peripheries (Serdar et al., 2000). Fine particles dominated the sediment in samples collected in 2009 near the Northlake Shipyard west of Gas Works (Ecology & Environment Inc. and Herrera, 2009).

TOC concentrations ranged from less than 0.01 percent to 35 percent, with a mean value of 7.3 percent (n = 242). TOC distribution is similar to the particle size distribution (Figure 4‐5). Sites with higher percentages of fines typically had higher concentrations of TOC. Values near the 3rd Ave W and Montlake CSO outfalls in the Fremont and Montlake cuts, respectively, were low relative to wider, slower regions of the study area. Decomposition of excess organic content in the sediments and the resulting decrease in DO may negatively impact benthic macroinvertebrates. Additionally, changes in redox potential and pH as a result of anoxia may impact the bioavailability of contaminants in sediment.

King County 4‐14 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 4-4. Percent of fines (silt and clay) in sediment at sampling sites in Lake Union/Ship Canal.

King County 4‐15 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 4-5. Percent of total organic carbon in sediment at sampling sites in Lake Union/Ship Canal.

King County 4‐16 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

4.6 Comparison of Chemical Concentrations to Criteria

Nearly all SMS chemical concentrations exceeded either the SCO or CSL at one or more sites in Lake Union/Ship Canal (Table 4‐4). The exceptions are ammonia, beta‐ hexachlorocyclohexane, endrin ketone, and selenium. The following chemicals most frequently exceeded the SMS:  Nickel (95 percent of sites)  TBT (89 percent of sites)  Total sulfides (78 percent of sites)  Arsenic (70 percent of sites)  PAHs (64 percent of sites)  Mercury (60 percent of sites)  Silver (59 percent of sites)  Bis(2‐ethylhexyl) phthalate (BEHP) (56 percent of sites)  Total PCBs (55 percent of sites)

Contaminants that exceeded the SMS for at least 5 percent of the sites were dibenzofuran (37 percent), lead (32 percent), cadmium (24 percent), copper (23 percent), monobutyltin (MBT) (23 percent), chromium (21 percent), dibutyltin (DBT) (13 percent), total DDEs (10 percent), carbazole (10 percent), di‐n‐butyl and di‐n‐octyl phthalates (both 9 percent), and tetrabutyltin (TeBT) (7 percent).

The high rate of SMS exceedances may be due in part to the selection bias toward contaminated sites, such as the sediments near CSO outfalls, Gas Works, Lake Union Steam Plant, and shipyards. Maps presenting relative exceedances of the SCO and CSL (in orders of magnitude) for each contaminant can be found in Appendix E.

Of the 375 sites sampled for at least one SMS contaminant in Lake Union/Ship Canal, 26 (6.9 percent) did not have an exceedance of the SMS for the chemicals analyzed; however, many of these sites were not tested for the full suite of SMS chemicals. Relative rates of exceedances for portions of the study area are as follows:  The least number of SMS exceedances are in the Montlake Cut and west of but not immediately next to the University CSO outfall in Portage Bay (Figure 4‐6).  Salmon Bay and Lake Union are highly contaminated relative to Portage Bay, the Montlake Cut, and Lake Washington’s Union Bay in terms of both the number of SMS exceedances and the magnitude of the exceedances.  The vicinities of Gas Works, Lake Union Steam Plant, and throughout nearshore Salmon Bay had the greatest rates of exceedances.

King County 4‐17 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table 4-4. Comparison of Lake Union/Ship Canal surface sediment chemical data to Sediment Management Standards.

Detection of Locations with Median Max. Concentrations Detection Limits Range of Ratio of Ratio of Frequency ≥ SMS ≥ SMS Detection Detected Detected of ≥ SCO & ≥ SCO Limits for Conc. to Conc. to Parameter SCO CSL Detection < CSL ≥ CSL & < CSL ≥ CSL Non-Detects SCO SCO

Ammonia 230 300 55/55 0/55 0/55 0 0 NA 0.34 0.96

(mg/kg-dw) (mg/kg-dw) Total sulfides 39 61 62/63 3/63 46/63 0 0 1.4 – 1.4 9.1 200 Conventionals Conventionals

Arsenic 14 120 270/297 178/297 29/297 22 0 4.8 – 50 2.3 82 Cadmium 2.1 5.4 275/304 71/304 3/304 1 0 0.2 – 3.6 0.76 8.3 Chromium 72 88 278/301 33/301 30/301 3 2 0.02 – 120 0.78 8.6 Copper 400 1,200 303/303 52/303 17/303 0 0 NA 0.6 28 Lead 360 > 1,300 313/313 98/313 2/313 0 0 NA 0.71 9.8 Mercury 0.66 0.8 302/309 24/309 162/309 2 0 0.05 – 0.8 1.3 65 Nickel 26 110 247/247 205/247 30/247 0 0 NA 2.2 25 Selenium 11 20 69/129 0/129 0/129 0 0 0.02 – 6.6 0.061 0.36

Metals (mg/kg-dw) Silver 0.57 1.7 146/182 47/182 61/182 13 17 0.012 – 3.1 2.3 37

Zinc 3200 305/305 1/305 1/305 0 0 NA 0.12 1.3

Benzoic Acid 2900 3,800 115/249 3/249 4/249 13 55 72 – 75,000 0.34 1.5 Beta- hexachloro- 7.2 11 0/84 0/84 0/84 9 52 1.4 – 1100 NA NA cyclohexane

dw) Bis(2- ethylhexyl) 500 22,000 164/254 137/254 4/254 61 5 30 – 10,000 4.3 8800 phthalate Organics (µg/kg- Organics Carbazole 900 1,100 82/120 2/120 10/120 0 0 13 – 600 0.26 5

King County 4‐18 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Dibenzofuran 200 680 192/279 51/279 52/279 18 23 0.02– 11,000 1.2 850 Dibutyltin 910 130,000 82/88 10/88 1/88 0 0 4.7 - 62 0.26 180 Dieldrin 4.9 9.3 5/90 0/90 1/90 10 64 1.9 – 37,000 0.12 3.5 Di-n-butyl 380 1,000 48/257 11/257 11/257 21 69 13 – 130,000 0.81 310 phthalate Di-n-octyl 39 > 1100 33/257 15/257 7/257 129 60 2 – 130,000 3.3 950 phthalate Endrin Ketone 8.5 > 8.5 0/84 0/84 0/84 0 66 1.9 – 2100 NA NA Monobutyltin 540 > 4,800 84/88 18/88 2/88 1 0 4.7 – 1200 0.26 93 Pentachloro- 1200 > 1,200 57/261 0/261 1/261 0 84 7.8 – 380,000 0.14 1 phenol Phenol 120 210 63/232 11/232 26/232 22 93 26 – 70,000 1.3 170 Tetrabutyltin 97 >97 56/83 0/83 6/83 0 0 1.1 - 61 0.31 7.9 Total PCB 110 2,500 151/209 108/209 7/209 26 2 3.4 – 4,200 2.5 120 Aroclors Total DDDs 310 860 36/96 2/96 0/96 12 11 0.49 – 37,000 0.12 2.8 Total DDEs 21 33 31/96 7/96 3/96 10 38 0.49 – 2100 0.57 2.1 Total DDTs 100 8,100 11/97 1/97 0/97 30 0 0.49 – 2100 0.04 1.4 Total PAHs 17,000 30,000 324/335 49/335 168/335 0 0 5.9 – 680 1.9 4,100 Tributyltin 47 320 107/111 30/111 69/111 1 0 5.5 – 130 19 5,300 Bolded chemicals exceeded the SMS for at least half of tested locations. SMS = Sediment Management Standards. SCO ‐= Sediment Cleanup Objective. CSL = Cleanup Screening Level.

King County 4‐19 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 4-6. Number of exceedances of Sediment Management Standards at 375 sampling sites in Lake Union/Ship Canal and 17 sites in Union Bay. Dot size indicates number of criteria parameters measured.

King County 4‐20 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Historical sources of contaminants include industrial discharges, maritime activity, stormwater and municipal wastewater outfalls (including CSOs), surface runoff, combustion, and aerial deposition.

Nickel concentrations were above the SCO throughout Lake Union/Ship Canal and Union Bay. Concentrations were generally similar with a median of 56 mg/kg‐dw (SCO = 26 mg/kg‐dw). Nickel appears to be fairly evenly distributed throughout the study area; however, some sites near Gas Works and in east Salmon Bay were one to two orders of magnitude greater than the median.

Throughout Lake Union/Ship Canal, the concentrations of high molecular weight PAHs (HPAHs) were typically two to five times higher than those of low molecular weight PAHs (LPAHs). The higher concentrations of HPAHs indicate that sources may be older (LPAHs degrade faster than HPAHs), that there is greater input of HPAHs than LPAHs, or both.

The contaminants of concern for sections of Lake Union/Ship Canal are discussed below.

4.6.1 Portage Bay and the Montlake Cut The majority of sampling in Portage Bay and the Montlake Cut occurred in 2011 and 2013 as part of the King County CSO Sediment Quality Characterization study (KC_CSO_2011; KC_CSO_2013). This study sampled 12 sites near the University CSO outfall and 7 sites near the Montlake CSO outfall. Other studies in Portage Bay were part of the King County monitoring program in 1986, 1989, 1995, and 2001 (LUUMON86; KC_old; LUUMON95; FWLKUN01) and the 1990 Ecology survey (LKUNION).

Key findings are as follows:  The following contaminants were found at one or more sites in Portage Bay and the Montlake Cut with a value above the SCO: total sulfides, cadmium, lead, mercury, nickel, silver, bis(2‐ethylhexyl) phthalate, di‐n‐butyl and di‐n‐octyl phthalates, total DDDs and DDTs, and total PCBs.  A 1990 Ecology site in the Montlake Cut showed exceedances for BEHP and nickel; the Montlake CSO outfall sediments sampled in 2011 did not have any exceedances for BEHP; metals were not measured at these sites in 2011.  One site northwest of the University CSO outfall near the shoreline had total PCB concentrations more than 100 times the SCO; the other sites had levels between one‐tenth and ten‐times the SCO, with higher concentrations near the shoreline.  Phthalate concentrations were greater toward the shoreline in the 2011 and 2013 University CSO sediment samples. These nearshore sediment samples had greater levels of fine sediment and TOC relative to samples further from the shoreline.  Contaminants of concern in Portage Bay and Montlake Cut sediments are total sulfides, cadmium, lead, mercury, silver, phthalates, and PCBs.  Unlike the rest of Lake Union/Ship Canal, elevated concentrations (values above the SCO) of total PAHs were not detected.

King County 4–21 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

4.6.2 Lake Union Sediment studies in Lake Union span from 1981 to 2014 and have focused primarily on the area surrounding Gas Works Park (GWPLKUNGWP; EPAGAS84; EPAGAS95; RETEC99; RETEC02; TAMU02; RJAC005), the Lake Union Steam Plant (SCLITE89), and the Densmore Drain outfall in Lake Union’s northeast arm (LUUCSO97; LUUCSO00; KC_CSO_2013). Other sampling includes King County sediment monitoring (LUUMON86; KC_old; LUUMON95; FWLKUN01; KingLakeSeds), a sediment survey by Ecology (LKUNION), sediments near drydocks (LKUNDRDK; UNIMAR), sediments near the National Oceanic and Atmospheric Administration (NOAA) Pacific Marine Center on the east side of Lake Union (NOAPMC94), sediments in south Lake Union near the Museum of History and Industry and the Center for Wooden Boats (SEACOM94; SLUPRK90), sediments at Dunato’s Boatyard on the northeast arm of Lake Union (DUNATO96), and sampling as part of the Northlake Shipyard cleanup (NorthlakeSediment09).

Key findings are as follows:  The contaminants found throughout Lake Union are total sulfides, arsenic, cadmium, chromium, lead, mercury, nickel, silver, phthalates, TBT, total PAHs, and total PCBs.  Copper, carbazole, dibenzofuran, and total DDD/DDE/DDTs were not as wide‐ spread; exceedances of the SCO for these contaminants occurred less commonly.  Elevated concentrations of contaminants were typically found near Gas Works Park, Lake Union Steam Plant, Lake Union Drydock, and Dexter Ave CSO outfall.  Silver concentrations were greater in Lake Union than in Salmon, Portage, and Union bays. The maximum concentration was 21.2 mg/kg‐dw and was detected near the Dexter Ave CSO outfall; this concentration is nearly 20 times the median silver value for the study area.  The Dexter Ave CSO site also had the greatest concentration of ammonia (221 mg/kg‐dw), lead (3,522 mg/kg‐dw); and PCB Aroclor 1248 (1,054 µg/kg‐dw).

Gas Works Park The sediments near Gas Works Park are highly contaminated. Widespread contaminants are total sulfides, metals (arsenic, cadmium, chromium, copper, lead, mercury, nickel, and silver), phthalates, carbazole, dibenzofuran, TBT, total PAHs, and total PCBs. Additionally, total DDDs, DDEs, and DDTS and zinc had one exceedance each of the SCO.

In terms of number and magnitude of exceedances, the primary contaminants of concern near Gas Works Park are total PAHs. PAH concentrations are greatest near the shoreline and decrease moving farther from the shore. PAHs in the sediment near Gas Works Park are between 10 and 4,000 times the SCO (SCO = 17,000 µg/kg‐dw).

Although the sediments containing sandblast grit near and under the Northlake Shipyard west of Gas Works Park were dredged and capped, the surrounding sediments exceed the SCO for contaminants associated with sandblast grit (PAHs and heavy metals—arsenic,

King County 4–22 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal cadmium, chromium, copper, lead, mercury, and silver). This area has elevated levels of arsenic, cadmium, mercury, silver, and zinc compared to the area east of Gas Works Park.

Lake Union Steam Plant The sediments near the decommissioned Lake Union Steam Plant are contaminated with PCBs; 8 of 10 ten sites sampled near the steam plant exceed the SCO for total PCBs (maximum = 2,500 µg/kg‐dw). Additional contaminants found above the SCO in at least one site were total sulfides, arsenic, cadmium, chromium, copper, lead, mercury, nickel, silver, phthalates, dibenzofuran, TBT, and total PAHs.

Densmore Drain In 1994, the University Regulator separation project was completed. The project diverted stormwater from the Densmore drain, Green Lake, and a segment of I‐5 from the County’s north interceptor sewer system to a new outfall in Lake Union’s northeast arm. Sediments downstream of the outfall were sampled in 1990 to establish baseline conditions and sampled again in 1997, 2000, and 2013 (LUUCSO97; LUUCSO00; KC_CSO_2013).

The sediments near the outfall were found to be either similarly or less contaminated than sites in other areas of Lake Union. In terms of SCO exceedances, the primary contaminant of concern near the outfall is BEHP. Total PAHs and PCBs are also elevated near the outfall relative to concentrations in the deeper center channel of the northeast arm.

4.6.3 Salmon Bay and the Fremont Cut The majority of sampling in Salmon Bay was completed by Ecology in 1996 and 1997 (SALMII96; SALMIII97). Additional sampling includes King County sediment monitoring (LUUMON86; LUUMON95; FWLKUN01), the 1990 Ecology survey (LKUNION), shipyard dredging assessments and NPDES monitoring (MARCO90; TRIMA90; FVO92; FOSS95; TRI_STAR; LIPDS04), a remedial investigation (JT_2014), and a boatyard runoff assessment (AJOH0049). The Fremont Cut was sampled in the northwest end near the 3rd Ave W CSO outfall (KC_CSO_2011); only organic compounds and physical parameters were measured.

Three dredging assessments in Salmon Bay included cores that exclusively sampled the biologically active sediment layer and were thereby not included in this analysis (TRIMA90; POSFT04; SALMO12). Of note, however, is that some of the sediments were deemed unsuitable for open‐water disposal in Elliott Bay because of contamination level.

Key findings of sediment sampling in Salmon Bay and the west end of the Fremont cut are as follows:  Sediments are contaminated throughout with organotins, heavy metals, phthalates, dibenzofuran, PCBs, and PAHs.  Concentrations of the following contaminants at one or more sites were above the SCO or CSL: total sulfides, arsenic, cadmium, chromium, copper, lead, mercury,

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nickel, silver, zinc, BEHP, di‐n‐butyl and di‐n‐octyl phthalates, dibenzofuran, DBT, MBT, TeBt, TBT, total PAHs, and total PCBs.  Contaminant concentrations are usually greater nearshore than in the main channel, but elevated concentrations (relative to SMS criteria) occur throughout the area.  Heavy metals, BEHP, butyltin, dibenzofuran, total PCBs, and total PAHs concentrations were typically lower in southeast Salmon Bay and the northwest end of the Fremont Cut than in Lake Union and other parts of Salmon Bay but were still above the SCO or the CSL at some sites.

4.7 Comparison of Bioassay Results to Criteria

Methods of the bioassay tests completed in Lake Union/Ship Canal were not consistent between studies, and quality control issues preclude complete analysis. At least one toxicity bioassay was assessed at 93 sites in Lake Union/Ship Canal. Of these sites, 65 met the state requirements for comparison to the SMS: using two species (C. tentans and H. Azteca), at least three tests, at least one chronic test, and at least one sublethal test (WAC 173‐204‐ 563). For 31 of the 65 sites, quality control (QC) issues occurred with the laboratory control sample, reference sample, or both. The three most common acute toxicity tests in terms of number of sites were the C. tentans 10‐day growth and 10‐day mortality tests (42 and 66 sites) and the H. azteca 10‐day mortality test (83 sites). The most common chronic test was the C. tentans 20‐day mortality test (25 sites). Figure 4‐7 shows the bioassay results for each site. Appendix E gives results for each site and test.

QC failures were most common for the C. tentans 10‐day growth and mortality tests (33.3 percent and 20 percent of studies, respectively); the H. azteca 28‐day growth test failed in the one study where it was attempted (RJAC005). Failures occurred in both negative laboratory controls and reference samples; reference sample failures were more frequent.

Figure 4‐8 displays bioassay data compared to the SMS, including sites with QC issues or an insufficient number of tests. Insufficient number of tests signifies that the study did not meet the state requirement for number and variety of tests. However, the figure indicates sites where at least one test failed the CSL criteria despite an insufficient number of tests.

Violations of the biological CSL criteria were detected in Salmon Bay, southern Lake Union, near Gas Works Park, and in Lake Union’s northeast arm. The Ecology survey of Salmon Bay in 1997and other smaller sampling efforts provide insights into the multiple hot spots of toxicity. Bioassay tests were completed less often for Portage Bay, and no samples were taken in the Montlake Cut.

A number of sites near Gas Works Park were found to be in violation of the CSL, did not have any violation of the CSL or SCO, or had an insufficient number of tests to assess benthic toxicity. This spatial heterogeneity may reflect the various levels of sediment contamination near the park or the different bioassay tests used in the different studies.

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Ecology (2003) and Serdar et al. (2000) noted that C. tentans bioassays were the most sensitive near Gas Works Park and in Salmon Bay. Ecology (2003) suggested that C. tentans, because of their infaunal habit, are more likely than epifaunal H. azteca to be affected by contaminants closely associated with the solid phase and/or may not readily partition into the overlying water column. Toxicity was also found in H. azteca bioassay tests but less frequently and most likely only at sites with higher levels of bioavailable contaminants in the water overlying the sediments.

4.8 Chemicals without Numeric Criteria

Washington State does not have standards to regulate concentrations of PBDEs or dioxins/furans in sediments. PBDEs and dioxin/furans may cause ecological effects because of their persistence and ability to biomagnify in the food chain. PBDEs are flame retardants used in a wide variety of products and are chemicals of emerging concern because of their toxicity and bioaccumulative properties. While some of the most common PBDEs have been banned, they are still detected in environmental and tissue samples. Dioxin/furan compounds are formed as an unintended byproduct during combustion of organic compounds in the presence of chloride. Sources include waste incinerators, pulp mills, and industrial processes.

4.8.1 PBDEs PBDEs were examined in 2010 at a site in the middle of Lake Union (KingLakeSeds); a total of 94.9 µg/kg‐dw of PBDE congeners was detected (Table 4‐5). The dominant congener was DecaBDE‐209, a PBDE that is still manufactured.

Table 4-5. Polybrominated diphenyl ether (PBDE) sediment concentrations (µg/kg-dw) at a site in central Lake Union (2010). PBDE Concentration ΣDecaBDE 92.80 ΣHexaBDE < 0.18 ΣPentaBDE 0.90 PentaBDE-99 0.76 PentaBDE-100 0.14 ΣTetraBDE 1.17 ΣTriBDE < 0.12 “<” indicates concentrations below the method detection limit.

4.8.2 Dioxin/Furans As part of the remedial investigation for the Lower Duwamish Waterway Superfund site, dioxin/furan concentrations in four surface samples in Lake Union/Ship Canal and one surface sample in Union Bay were measured in 2005 to provide background levels for the area (LDWRRUN0). Two samples were taken from Salmon Bay near the 11th Ave CSO outfall (SC‐SS1A and B), and two were taken between Lake Union and Portage Bay beneath the I‐5 bridge (LU‐SS9A and B). The Union Bay sample was taken near the Belvoir CSO (UB‐ SS8). Data are presented in Table 4‐6. Dioxins/furans were detected in every sample.

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Individual congener concentrations ranged from < 0.056 ng/kg‐dw to 208,000 ng/kg‐dw. Concentrations were greatest at the site closest to the 11th Ave W CSO outfall.

King County 4–26 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure 4-7. Bioassay data and comparison to Sediment Management Standards for sediment sampling sites in Lake Union/Ship Canal. Rose and teal colored slices in pinwheel legend indicate acute and chronic toxicity tests, respectively.

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Figure 4-8. Sediment bioassay results compared to Sediment Management Standards for sediment sampling sites in Lake Union/Ship Canal.

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Table 4-6. Dioxin/furan results (ng/kg-dw) at four Lake Union/Ship Canal and one Union Bay sediment sampling site (2005). Laboratory qualifiers are provided. Salmon Bay/11th Ave W CSO Lake Union/Portage Bay Union Bay Congener SC-SS1A SC-SS1B LU-SS9A LU-SS9B UB-SS8 2,3,7,8-TCDD 1.26J 2.05J 0.328J 1.08J 3.01J 1,2,3,7,8-PeCDD 6.64J 9.6J 1.32J 5.27J 11.8J 1,2,3,6,7,8-HxCDD 86.7 63 5.84J 30.2J 62.6 1,2,3,4,7,8-HxCDD 35.5 18.4J 1.48J 7.14J 21.2J

Dioxins Dioxins 1,2,3,7,8,9-HxCDD 88.4 52.2 3.45J 19.9J 51 1,2,3,4,6,7,8-HpCDD 8740 1990 138 755 1320 OCDD 208,000 20,000 1000 5660 8280 2,3,7,8-TCDF 6.63 12.6 0.443J 3.64 6.14 1,2,3,7,8-PeCDF 3.97J 6.88J 0.668J 2.54J 4.69J 2,3,4,7,8-PeCDF 6.21J 10.1J 0.754J 3.5J 6.76J 1,2,3,4,7,8-HxCDF 18J 17J 1.43J 7.62J 15J 1,2,3,6,7,8-HxCDF 9.66J 16.3J 1.55J 5.13J 14.4J 1,2,3,7,8,9-HxCDF 0.56UJ 0.711J 0.303J 0.707J 0.858J Furans Furans 2,3,4,6,7,8-HxCDF 7.42J 13.5J 1.25J 5.69J 10.8J 1,2,3,4,6,7,8-HpCDF 162 259 22.6J 120 222 1,2,3,4,7,8,9-HpCDF 15.5J 13.6J 6.45J 9.75J 12.8J OCDF 714J 692 66.1 399 517 J = an estimated value. U = a non‐detect with a concentration below the provided value.

4.9 Benthic Macroinvertebrate Communities

Alongside the August/September 2001 sediment chemistry samples, benthic macroinvertebrate samples were obtained at 15 sites in Lake Washington and Lake Union/Ship Canal using a Petite Ponar sampler (0.0231 m2). Five replicate samples were collected at each station. The benthic samples were first preserved using a 10 percent buffered formalin solution with rose bengal added as a biological stain to enhance invertebrate identification. After approximately two weeks, the samples were transferred to a 70 percent ethyl alcohol solution. KCEL sorted the samples into major groups (such as oligochaetes or diptera) using low power microscopes. EcoAnalysts, Inc., further identified the samples to the lowest practical taxonomic level.

Throughout Lake Union/Ship Canal, oligochaetes were the dominant taxa, composing 48.6 percent of all organisms identified, and the dominant taxon at 9 of the 15 sites (Table 4‐7). Copepods, specifically of the order Harpacticoida, were secondarily dominant (19.4 percent of organisms and dominant at 3 of 15 sites), and chironomids (of the order Diptera) were the third dominant taxa (9.3 percent and dominant at 1 of 15 sites [0539 in southern Portage Bay]). Freshwater clams composed 7.7 percent of organisms sampled and were dominant at one site (0564 in northeast arm of Lake Union), and nematodes composed 2.5 percent and were dominant at one site (0567in southeast Lake Union).

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Table 4-7. Benthic macroinvertebrate data from 15 sites in Lake Union/Ship Canal (2001). First Dominant Percent Total Organism Oligochaetes Depth Abundance Total Shannon’s and Site Location (m) (org/m2) Richness Taxon % H’ (base e) Chironomids HBI Limnodrilus 0513 East end of Fremont Cut 12 12,026 15 89.1 0.55 99.1 8.2 hoffmeisteri 0539 South Portage Bay 4 5,810 39 Paratanytarsus sp. 14.2 2.58 50.8 6.5 0563 Central Portage Bay 8 1,030 19 Enchytraeidae 30.3 1.74 44.5 8.6 0564 NE arm Lake Union 10 3,697 25 Bivalvia 41.0 1.92 32.1 8.1 Tubificidae w/ cap 0565 NE Lake Union 10a 1,593 9 26.1 1.53 71.7 8.6 setae 0566 East-central Lake Union 15 4,398 7 Harpacticoida 35.0 1.40 63.2 8.0 0567 SE Lake Union 8 4,545 29 Nematoda 30.9 1.93 57.9 7.3 0568 South Lake Union 12 14,719 11 Harpacticoida 56.8 1.24 42.5 8.8 0569 SW Lake Union 15 11,896 9 Harpacticoida 60.3 1.02 51.3 7.6 Tubificidae w/ cap 0570 Central Lake Union 13 1,333 9 26.0 1.41 85.7 8.2 setae Limnodrilus 0572 NW Lake Union 13 1,965 13 40.1 1.57 60.4 8.8 hoffmeisteri Limnodrilus 0573 West end of Fremont Cut 7 3,723 38 20.5 2.41 56.5 7.3 hoffmeisteri Tubificidae w/ cap 0574 East Salmon Bay 6 12,823 31 31.2 1.65 65.7 8.5 setae Tubificidae w/ cap 0575 West-central Lake Union 15 2,052 9 42.2 1.47 78.1 8.4 setae Limnodrilus 0580 West Salmon Bay 8 9,056 23 60.5 1.33 78.1 9.0 hoffmeisteri a Depth at site 0565 was not measured when sampled. Depth was estimated from a bathymetric map. HBI = Hilsenhoff Biotic Index (1: most sensitive species; 10: most tolerant species).

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The greatest diversity (39 taxa; Shannon’s H’e: 2.58) was found in southern Portage Bay, followed by a site with 38 taxa in the west end of the Fremont Cut (Shannon’s H’e: 2.41). The least diverse site is at the east end of the Fremont Cut (0513) with 15 taxa (Shannon’s H’e: 0.55); this site was dominated by Limnodrilus hoffmeisteri, an oligochaete, which composed 89 percent of enumerated individuals. The second least diverse site is in southwestern Lake Union near the Dexter Ave CSO (0569) with 9 taxa (Shannon’s H’e: 1.022); this site was dominated by harpatacoids (60.3 percent) and Naididae (formerly classified as Tubificidae) (25.2 percent).10

The tolerance values from Lenat (1993) and Wildhaber and Schmitt (1988) indicate that tolerant taxa were dominant throughout Lake Union/Ship Canal. Hilsenhoff Biotic Indices (HBIs) (1 = most sensitive species; 10 = most tolerant species) ranged from 6.5 to 9.0. The site with the most tolerant community was in western Salmon Bay (0580); the site with the most sensitive community was in southern Portage Bay site (0539), although tolerant taxa were more numerous than sensitive taxa at this site. Oligochaetes and chironomids often dominate in polluted sediments because of their tolerance to pollutants.

The 2001 benthic macroinvertebrate diversity and tolerance analysis was inconclusive in regard to defining a relationship between concentrations of contaminants and the benthic community (King County, 2004a). The indices are affected by changes in habitat beyond concentrations of contaminants, such as salinity, grain‐size structure, substrate, TOC, oxygen availability, and depth. However, it is apparent that the benthic communities of Lake Union/Ship Canal are predominately composed of pollution‐tolerant taxa, exhibiting limited biodiversity. The least impacted sites (pollutant‐sensitive and diverse benthos) are in southern Portage Bay (0539), the west end of the Fremont Cut (0573), and southeast Lake Union (0567). The benthos of Lake Union/Ship Canal are more tolerant and less diverse than the benthos in Lake Washington and Lake Sammamish, possibly because Lake Union/Ship Canal has a greater level of sediment contamination (King County, 2004a).

Benthic macroinvertebrates were also monitored as part of the University Regulator separation project. Baseline, pre‐separation conditions were assessed between 1986 and 1993 near the Densmore Drain outfall and in central Lake Union. Post‐separation conditions were assessed in 1996, 1997, and 2000. Between 1986 and 2000, community diversity and evenness increased and dominance decreased near the Densmore Drain outfall; conditions at the upstream control site in Union Bay and the site in central Lake Union remained relatively consistent (EcoAnalysts, 2000).

4.10 Summary

The analysis of available data found areas of elevated concentrations of contaminants in sediment and benthic invertebrate toxicity throughout Lake Union/Ship Canal as the result of historical and/or current outfall discharge and depositional sites. Sediment chemistry conditions in the study area may cause adverse effects for aquatic organisms.

10 Species diversity, a measure of number of species and the distribution/evenness of their abundance, is represented by the Shannon Diversity Index (H′).

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Major sediment sampling and analysis findings were as follows:  The sediments of Salmon Bay and Lake Union are highly contaminated compared to sediments of Portage Bay, the Montlake Cut, and Lake Washington’s Union Bay in terms of both number of SMS exceedances and the magnitude of the exceedances.  Bioassay analysis found that many sites in Salmon Bay and Lake Union were toxic. C. tentans was the most sensitive bioassay. The toxicity of the sediments in Lake Union near Gas Works Park varied spatially and by study.  In Lake Union and Salmon Bay, the most widespread contaminants were metals (nickel arsenic, mercury, silver, lead, copper, and chromium), TBT, total sulfides, total PAHs, phthalates, total PCBs, and dibenzofuran. o PAHs, dibenzofuran, and some heavy metal concentrations were greatest near Gas Works Park, the former gasification plant. o In Salmon Bay, hot spots of contamination are interspersed among a field of more moderate concentrations; the hot spots generally occurred in nearshore areas.  Sediments in Portage Bay and the Montlake Cut were less contaminated than in Salmon Bay and Lake Union, although exceedances of SMS criteria for total sulfides, cadmium, lead, mercury, silver, phthalates, and total PCBs were found in Portage Bay and the Montlake Cut. Notably, Portage Bay and Montlake Cut had no exceedances of the SMS criteria for total PAHs, unlike the remainder of Lake Union/Ship Canal.  Nickel concentrations were above the SCO in Lake Union/Ship Canal. Nickel appears to be fairly evenly distributed throughout the study area; similar concentrations were found in Lake Washington’s Union Bay.  Nearshore sediments and sediments near docks typically had higher concentrations of TBT, mercury, phthalate, PAHs, and carbazole than sediments at other sites.  Implications of sediment conditions on benthic communities are as follows: o The benthos of Lake Union/Ship Canal are more tolerant and less diverse than benthos in Lake Washington and Lake Sammamish, consisting predominately of oligochaetes, copepods, and chironomids. o Salmon Bay studies suggest that PAHs, carbazole, BEHP, chromium, silver, arsenic, and TBT may be complementary causes of toxicity (Serdar et al., 2000). o Low DO content in Lake Union/Ship Canal as the result of decomposition of excess organic content in sediments may further impact benthic macroinvertebrates.

The increased salinity of pore water from saltwater intrusion may limit biotic activity (Rogowski, 2000). The pH and DO changes associated with saltwater intrusion likely alter the solubility and bioavailability of contaminants in Salmon Bay and the rest of Lake Union. Further study is needed to determine the impacts of the saltwater intrusion on the bioavailability and toxicity of contaminants in Lake Union/Ship Canal.

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5.0 TISSUE CHEMISTRY Fish and shellfish tissue data are very limited for Lake Union/Ship Canal. Few studies have been completed. The most recent studies of tissue in Lake Union/Ship Canal did not follow standard sampling and quality assurance protocol. These studies are discussed in detail in Appendix F.

The consensus of these studies is that benthivores (such as suckers and sculpin) had greater exposure to contaminated sediments and thus showed physiological indicators of chronic toxicity and elevated levels of contaminants. Predator species (such as bass and pikeminnow) also showed elevated contaminant levels, suggesting that some contaminants including arsenic, methylmercury, and PCBs are accumulating through trophic levels.

Further study and analysis are necessary to understand the persistence of contaminants in relation to tissue levels, the threat to human health via tissue consumption, and the movement of contaminants through the trophic levels in Lake Union/Ship Canal.

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6.0 FINDINGS AND DATA LIMITATIONS This chapter presents the major findings and data limitations identified from the analyses of water and sediment quality data in Lake Union/Ship Canal.

6.1 Findings

The following sections summarize water and sediment quality findings for Lake Union/Ship Canal.

6.1.1 Water Quality The main water quality issues in Lake Union/Ship Canal are high bacteria concentrations, high temperatures in surface waters in the summer, and low DO concentrations in Lake Union’s bottom waters in the summer. More data are needed on the seasonal and spatial variability of metals and organics concentrations to fully evaluate their potential impact on water quality.

Major findings are as follows:  Bacteria. From a regulatory and human‐health standpoint, elevated bacteria concentrations (as measured by fecal coliform bacteria) are a persistent water quality issue in Lake Union/Ship Canal. Bacteria concentrations are typically greatest near the Locks and decrease moving upstream, likely because the dominant circulation pattern in the system pushes the bacteria westward toward the Locks. Despite continuing frequent water quality criteria failures, bacteria concentrations have declined in the last several decades. CSO control and improved stormwater management may have contributed to this decline. Other sources of bacteria need to be identified and mitigated in order to further enhance water quality and protect human health.  Temperature and DO. The high temperatures and low DO content in Lake Union/Ship Canal threaten salmonids and other aquatic life at certain times of year. During the summer salmonid migration, temperatures of the surface 10 m exceed thermal stress and direct mortality thresholds. By late summer, temperatures can exceed the thermal stress threshold even in the hypolimnetic waters below 10 m. The stress is further intensified by low DO conditions where hypolimnetic hypoxia/anoxia prevents adequate refuge from high water temperatures by making the cooler waters inhospitable. Over the past three decades, surface temperatures in Lake Union/Ship Canal have increased, temperatures of the summer hypolimnion have decreased, and thermal stratification has strengthened.  Salinity. The conditions in Lake Union/Ship Canal are substantially influenced by the intrusion of salt water via the Locks during the summer; the amount varies greatly year to year. Over the course of the summer, salinity along the bottom increases. A saltwater layer in some years may reach as far upstream as Portage Bay and Lake Washington. After Locks usage has decreased in the fall and winter,

King County 6–1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

saltwater pockets may remain in the deep holes of the Lake Union basin, preventing mixing and prolonging anoxic and acidic conditions. Increased concentrations of metals, organic compounds, and nutrients were observed near the lake bottom during an extended period of saltwater intrusion in 2002–2003. The influence of the saltwater layer on sediment chemistry and resuspension is the most likely cause of these increases.  Clarity. The clarity of Lake Union/Ship Canal is influenced by phytoplankton biovolume and inputs of particles from stormwater runoff and CSOs. Overall, transparency has increased or remained constant over the past 30 years.  pH and alkalinity. pH and alkalinity respond to biotic activity in Lake Union/Ship Canal. pH rises during the spring phytoplankton bloom, and acidic conditions appear in the hypolimnion from the decomposition of detritus during the summer and early fall. pH levels occasionally exceeded the Washington State water quality criterion during the spring bloom.  Nutrient concentrations. Nutrient concentrations in Lake Union/Ship Canal are affected by inputs from Lake Washington and Union Bay via the Montlake Cut, from CSO and stormwater outfalls, and from internal loading from the lake’s sediments. Nutrient concentrations in the system have decreased over the years. The decreasing trends suggest that loading both from Lake Washington and the immediate Lake Union/Ship Canal watershed has decreased.  Chlorophyll a. Concentrations of chlorophyll a provide information on the level of phytoplankton productivity and biovolume in a lake. No substantial long term trends for chlorophyll a were observed from the mid‐1980s to present. Analysis of data from 1997 to present, however, indicates decreasing trends in spring and summer concentrations.  Phytoplankton growth and abundance. Phosphorus appears to be the most frequent limiting factor for phytoplankton growth and abundance. Nitrogen may be co‐limiting during the summer. The short hydraulic residence time may limit phytoplankton buildup and abundance but also may introduce blooms from Lake Washington. Zooplankton grazing may curb phytoplankton, but data are too limited to support this assumption. Phytoplankton communities are dominated by a spring bloom that features diatoms accompanied by cryptophytes to a lesser degree. Phytoplankton diversity peaks in the late summer when chlorophytes and cyanobacteria make up a greater portion of the overall population. A minor fall bloom, typically dominated by the diatom genera Tabellaria and Fragilaria, occurs in Lake Union.  Metals. The most recent metals data indicate that concentrations in Lake Union/Ship Canal have not exceeded the Washington State water quality criteria for aquatic life or the EPA Human Health Criteria. Arsenic, copper, lead, mercury, nickel, and zinc were elevated in Salmon Bay near the Locks relative to the rest of Lake Union/Ship Canal. The Montlake Cut site had the lowest concentrations of these metals, suggesting that the metals are entering Lake Union/Ship Canal from the immediate watershed or sediments.

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 Organic chemicals. The most frequent detections of organic chemicals occurred at the Locks site and the hypolimnion at the Dexter site in south Lake Union. PAHs were detected most often in the hypolimnion, likely from resuspension of the sediments. Detections of PAHs in the epilimnion suggest external loading and upward mixing from the hypolimnion. PCBs and bis(2‐ethylhexyl)phthalate were sometimes detected in the limited number of samples collected at concentrations exceeding the EPA Human Health Criteria. Although data indicate that concentrations of other organic compounds have not exceeded water quality criteria, the older samples typically had detection limits above many of the water quality criteria and had higher frequencies of blank contamination. Little is known about chemicals of emerging concern, including many pharmaceuticals, pesticides, and flame‐retardants currently in use.

6.1.2 Sediment Quality The analysis of available data found areas of elevated concentrations of contaminants in sediment throughout Lake Union/Ship Canal as the result of historical and currently operating outfalls and depositional sites. Sediment chemistry conditions in the study area may cause adverse effects for aquatic organisms.

Metals, PAHs, PCBs, butyltins, and phthalates are the chemicals of highest concern in sediments. PBDEs may also be of concern. Monitoring of PBDEs should continue because of their propensity to bioaccumulate and the potential for future establishment of state PBDE criteria.

Salt water that enters the system from operation of the Locks can facilitate the release and resuspension of nutrients and contaminants from the sediments.

Major findings are as follows:  The sediments of Salmon Bay and Lake Union are highly contaminated compared to sediments of Portage Bay, the Montlake Cut, and Lake Washington’s Union Bay in terms of both number of SMS Sediment Cleanup Standards exceedances and the magnitude of the exceedances.  Bioassay analysis found that many sites in Salmon Bay and Lake Union are toxic. C. tentans was the most sensitive bioassay. The toxicity of the sediments in Lake Union near Gas Works Park varied spatially and by study.  In Lake Union and Salmon Bay, the most widespread contaminants were metals (nickel arsenic, mercury, silver, lead, copper, and chromium), TBT, total sulfides, total PAHs, phthalates, total PCBs, and dibenzofuran.  Sediments in Portage Bay and the Montlake Cut were less contaminated than in Salmon Bay and Lake Union, although exceedances of SMS criteria for total sulfides, cadmium, lead, mercury, silver, phthalates, and total PCBs were found in the sediments of Portage Bay and the Montlake Cut. Notably, Portage Bay and the Montlake Cut had no exceedances of the SMS criteria for total PAHs, unlike the remainder of Lake Union/Ship Canal.

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 Nickel concentrations were above the SCO in Lake Union/Ship Canal. Nickel appears to be fairly evenly distributed throughout the study area; similar concentrations were detected in Lake Washington’s Union Bay.  Nearshore sediments and sediments near docks typically had higher concentrations of TBT, mercury, phthalate, PAHs, and carbazole than other sites.  Implications of sediment conditions on benthic communities are as follows: o Lake Union/Ship Canal benthos are predominately composed of pollution‐ tolerant taxa, exhibiting limited biodiversity. o The least impacted sites (pollutant‐sensitive and diverse benthos) are in southern Portage Bay, the west end of the Fremont Cut, and southeast Lake Union. o The benthos of Lake Union/Ship Canal are more tolerant and less diverse than the benthos of Lake Washington and Lake Sammamish.

6.2 Next Steps in the Water Quality Assessment and Monitoring Study

Efforts over the years to clean up historical pollution and to control sources of pollutants into Lake Union/Ship Canal, such as CSO control and green stormwater infrastructure, are improving both water and sediment quality in the system. Other projects are planned. All King County and City of Seattle CSOs in the area will be fully controlled by 2030; cleanup of contaminated sites, such as Gas Works Park, will decrease the leaching of contaminants into the study area; and USACE is investigating methods to decrease summer water temperatures and maintain acceptable DO levels for migrating salmonids.

As a next step in King County’s Water Quality Assessment and Monitoring Study, area reports such as this one are being prepared to describe existing conditions and identify long‐term trends in Elliott Bay and the Duwamish Estuary. Data gaps identified in the three area reports are described and prioritized in another report, followed by reports on the three studies selected to help fill priority gaps. Two reports will document existing loadings and estimate future loadings of pollutants from various pathways including stormwater and CSOs to the three study areas. Finally, a synthesis report will summarize results of the studies and recommend additional studies to enhance water quality improvement work in the region.

King County will use the information from the study to inform the next CSO control plan update, including identification of opportunities to reduce costs of CSO control projects, establishing baseline conditions for post‐construction monitoring of CSO control projects, and deciding whether to pursue an integrated CSO control plan.

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6.3 Potential Future Studies

Additional data are needed to gain a greater understanding of existing conditions and the effects of planned improvements on future conditions in Lake Union/Ship Canal. Information on the impacts of CSOs and the benefits of CSO control could be obtained through studies that identify sources of bacteria, the presence of sewage through use of conservative tracers, concentrations of contaminants of emerging concern, characteristics of sediments and sediment contamination, sedimentation rates, and nutrient and contaminant loads from various sources.

In addition, fish and shellfish tissue in Lake Union/Ship Canal has seldom been examined; the most recent data cannot be used with high confidence because methods were poorly reported. New analyses that follow established protocols would provide insight into the impacts of highly contaminated sediments. More information is also needed on the quantity and type of fish and shellfish extracted from Lake Union/Ship Canal for consumption.

This section details important data limitations identified during the preparation of this report and recommends studies to supplement existing data and more fully characterize the Lake Union/Ship Canal system. Limitations and recommendations directly or indirectly linked to CSO impacts are presented first.

6.3.1 Data Limitations Directly or Indirectly Linked to CSO Impacts The following data limitations and recommended studies linked to CSO impacts were identified during preparation of this report:  Sources/pathways of bacteria. Sources and pathways (for example, CSOs, stormwater outfalls, illicit boat discharges, and houseboats) of bacteria into Lake Union/Ship Canal must be characterized to adequately address their abatement. Spatially explicit sampling conducted during dry and wet weather in Lake Union/Ship Canal can identify and examine the causes of hot spots of bacterial contamination.  Conservative sewage tracers. Tracers, such as pharmaceuticals, personal care products, and artificial sweeteners, could help determine whether fecal contamination is related to human feces or other sources such as dogs or waterfowl. The tracers could be used to prioritize CSO control projects and in post‐construction monitoring to document the reduction of sewage in receiving waters.  Contaminants of emerging concern. Contaminants of emerging concern (CECs) are chemicals that have been detected at low levels in surface water but whose risks to human health and the environment may not be known. They include pharmaceuticals, personal care products, and fire retardants. The levels of CECs in Lake Union/Ship Canal are unknown.  Sediment – current conditions. The most recent comprehensive sediment dataset for Lake Union/Ship Canal was collected in 2001. This dataset measured PCBs as

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Aroclor mixtures and not at the PCB congener level. PCB congener analysis could allow for fingerprinting contamination, determining likely sources, and comparing the contamination to toxicity equivalency factors. A new sediment characterization could be designed to answer these questions: o Have historically contaminated sediments been buried by deposited sediments? o Do these sediments still pose a threat to benthic species? o What is the sediment porewater salinity?  Sediment core dating and sedimentation rate. The sedimentation rate determined by Tomlinson et al. (1977) should be updated to reflect changes in watershed development, stormwater and CSO management, and radionuclide detection methods. An updated sedimentation rate would aid in estimating the age of sediments sampled. The knowledge of the spatial differentiation of sedimentation rates could be used to estimate dominant lake circulation patterns and the effects of CSO and stormwater outfalls on the rate of sedimentation. Sediment core dating and sedimentation rates would also help determine when and at what rate contaminants are entering Lake Union sediments. Sedimentation rates should be examined in the following areas: o Western and eastern Salmon Bay o The Fremont Cut upstream and downstream of the 3rd Ave W CSO outfall o Northwestern, southwestern, central, and northeastern Lake Union o Beneath the I‐5 bridge o Southern Portage Bay o Near the University CSO o The Montlake Cut upstream and downstream of the Montlake CSO  Fish tissue. Fish and shellfish tissue in Lake Union/Ship Canal has seldom been examined; the most recent data cannot be used with high confidence because methods were poorly reported. New analyses that follow established protocols would provide insight into the impacts of highly contaminated sediments. More information is also needed on the quantity and type of fish and shellfish extracted from Lake Union/Ship Canal for consumption. A survey of lake users could provide this information. The studies could answer the following questions: o Are identified contaminants moving through trophic levels, from the sediments to benthic invertebrates to benthivores to predators? o Do the chemical levels in fish and shellfish tissue pose a threat to human health?  Nutrient and contaminant loads. The calculation and prediction of nutrient and contaminant loads from stormwater, CSOs, Lake Washington’s Union Bay, and salt water entering through the Locks would provide numeric rationale for determination of the main sources of concern and would allow for estimation of the internal load from Lake Union sediments.

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6.3.2 Other Data Limitations The following are other data limitations and recommended studies identified during preparation of this report:  Bacteria levels at South Lake Union Park. Because of the potential entrainment of stormwater and CSO effluent in south Lake Union, elevated bacteria concentrations may be present for several days after a storm event. Swimmers and other in‐lake users may be exposed. Sampling for bacteria near the canoe launch in South Lake Union Park could provide insight into the risk of exposure.  Impacts of saltwater intrusion on release and bioavailability of sediment contaminants. If substantial volumes of salt water are allowed to enter through the Locks and travel into Lake Union, anoxia near the sediments can persist for many months. The duration depends on the concentration of salt water at this depth. Reducing conditions could promote the release of nutrients, metals, and organic compounds from the contaminated sediments. These chemicals could then enter the water when the lake turns over in the fall. Characterization of the concentrations, forms, and bioavailability of the released chemicals and their potential consequences could inform operation strategies of the Locks.  Impacts of zooplankton on phytoplankton. Little is known on the composition, magnitude, and predation pressures on zooplankton populations of Lake Union. Without this knowledge, it is difficult to determine whether algae blooms generally decline from lack of nutrients or from grazing pressure. Quantitative information is needed on zooplankton predation and its effects on the floral‐faunal balance.  Cyanobacteria toxin production. Sampling for cyanotoxins (such as microcystin and anatoxin) would provide insight on the threat to swimmers and other lake users posed by late summer blooms of cyanobacteria in south Lake Union.

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7.0 REFERENCES

Alabaster, J.S., D.G. Shurben, and G. Knowles. 1979. The effect of dissolved oxygen and salinity on the toxicity of ammonia to smolts of salmon, Salmo salar L. Journal of Fish Biology 15: 705−712.

Arhonditsis, G.B., M.T. Brett, C.L. DeGasperi, and D.E. Schindler. 2004. Effects of climatic variability on the thermal properties of Lake Washington. Limnology and Oceanography 49: 256–270.

ATC Environmental, Inc. 1996. Site investigation report, John Dunato and Company, Dunato’s Marine Service and Supply, 2309 North Northlake Way, Seattle, Washington. Prepared for Washington State Department of Ecology, Seattle, WA.

Bechtel Jacobs Company, LLC. 2000. Improved methods for calculating concentrations used in exposure assessment. Prepared for the Washington State Department of Ecology. Report # BJC/OR‐416. pp 14−20. http://rais.ornl.gov/documents/bjc_or416.pdf.

Bidwell, J.R., and J.R. Gorrie. 2006. The influence of salinity on metal uptake and effects in the midge Chironomus maddeni. Environmental Pollution 139: 206−213.

Bower, C.E., and J.P. Bidwell. 1978. Ionization of ammonia in seawater: Effects of temperature, pH, and salinity. Journal of the Fisheries Board of Canada 35: 1012−1016.

Carlson, R.E. 1977. A trophic state index for lakes. Limnology and Oceanography 22: 361−369.

Carroll, J.V., and G.J. Pelletier. 1991. Diagnostic study of Lake Sawyer, King County, Washington. Washington State Department of Ecology. Olympia, WA.

CH2M HILL. 1975. Water circulation studies of Lake Washington. Prepared for Metro and City of Seattle, Seattle, WA.

City of Seattle. 1994. Lake Union water quality/environmental assessment: Volume 2 project report. City of Seattle, Department of Wastewater Utilities, Seattle, WA.

City of Seattle and USACE. 2008. Synthesis of Salmon research: investigations conducted in the western Lake Washington Basin. City of Seattle Public Utilities and U.S. Army Corps of Engineers, Seattle, WA.

City of Seattle. 2010. Shoreline characterization report. City of Seattle Department of Planning and Development, Seattle, WA.

King County 7–1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

City of Seattle. 2014. Draft executive summary for the plan to protect seattle’s waterways. City of Seattle, Seattle Public Utilities, Seattle, WA.

City of Seattle. 2015a. Integrated plan. Seattle Public Utilities, Seattle, WA.

City of Seattle. 2015b. Long‐term control plan. Seattle Public Utilities, Seattle, WA.

Cubbage, J. 1992. Survey of contaminants in sediments in Lake Union and adjoining waters (Salmon Bay, Lake Washington Ship Canal, and Portage Bay). Washington State Department of Ecology, Toxics Cleanup Program, Olympia, WA.

Davis, J.C. 1975. Minimal dissolved oxygen requirements of aquatic life with emphasis on Canadian species: A review. Journal of the Fisheries Research Board of Canada 32: 2295−2332.

Dickman, M. 1969. Some effects of lake renewal on phytoplankton productivity and species composition. Limnology and Oceanography 14(5): 660‐666.

Driggers, V. W. 1964. Tracer dye studies of Lake Union and Bellingham Bay. M.S. Thesis. University of Washington. 73 pp. Location: Fisheries Library, Seattle, WA.

EcoAnalysts, Inc. 2001. Benthic macroinvertebrate communities in Lake Union: Evaluating responses to the University Regulator combined sewer overflow control project. Prepared for King County Department of Natural Resources, Moscow, ID.

Ecology. 2002. Evaluating standards for protecting aquatic life in Washington's surface water quality standards temperature criteria, draft discussion paper and literature summary. Washington State Department of Ecology, Water Quality Program, Olympia, WA.

Ecology. 2003. Sediment toxicity near Gas Works Parks, Lake Union, Seattle. Prepared by R. Jack. Washington State Department of Ecology, Environmental Assessment Program, Olympia, WA.

Ecology. 2006. Chemical characterization of stormwater runoff from three Puget Sound boatyards. Prepared by A. Johnson, S. Golding, and R. Coots. Washington State Department of Ecology, Environmental Assessment Program, Olympia, WA.

Ecology. 2008. Sediment cleanup status report. Washington State Department of Ecology, Toxics Cleanup Program, Olympia, WA.

Ecology. 2013. Sediment Management Standards. Chapter 173‐204 WAC. Pub. No. 13‐09‐ 055. Washington State Department of Ecology, Toxics Cleanup Program, Olympia, WA.

King County 7–2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Ecology. 2015. Eyes over Puget Sound: Surface conditions report – December 14, 2015. Prepared by Christopher Krembs. Washington State Department of Ecology, Environmental Assessment Program, Olympia, WA. http://www.ecy.wa.gov/programs/eap/mar_wat/eops/EOPS_2015_12_14.pdf.

Ecology & Environment, Inc., and Herrera Environmental Consultants. 2009. Northlake Shipyard sandblast grit study, final project report, Seattle, Washington. Prepared for Washington State Department of Ecology, Seattle, WA.

Edmondson, W.T. 1977. Lake Washington. In North American project: A study of U.S. water bodies. A Report for the Organization of Economic Cooperation and Development. EPA‐600/3‐77‐086. U.S. Environmental Protection Agency, Corvallis, OR.

Edmonson, W.T. 1994. Sixty years of Lake Washington: A curriculum vitae. Lake and Reservoir Management 10: 75−84.

Environment Canada. 2001. Priority substances list assessment report: Road salts. Canadian Environmental Protection Act, 1999. Environment Canada, Health Canada, Minister of Public Works and Government Services 2001, Ottawa, Ontario.

EPA. 2014a. Great Lakes monitoring, air indicators, atmospheric deposition of toxic pollutants. Accessed 10/20/2014. http://www.epa.gov/greatlakes/glindicators/air/airb.html.

EPA. 2014b. USEPA national functional guidelines for Superfund organic methods data review (SOM02.2). EPA 540‐R‐014‐002. Washington, DC.

EPA. 2014c. USEPA national functional guidelines for inorganic Superfund data review (ISM02.2). EPA 540‐R‐013‐001. Washington, DC.

Foster, R.F. 1943. Sources of pollution of Lake Washington Canal and Lake Union. Washington State Pollution Commission, Bulletin No. 28.

GeoEngineers. 2013. Supplemental investigation work plan, Gas Works Park Site, Seattle, Washington. Prepared for Puget Sound Energy, Seattle, WA.

Gilpina, L.C., K. Davidson, and E. Roberts. 2004. The influence of changes in nitrogen: Silicon ratios on diatom growth dynamics. Journal of Sea Research 51: 21−35.

GLWTC. 2001. Greater Lake Washington Technical Committee. Reconnaissance assessment—Habitat factors that contribute to the decline of salmonids. Draft. Prepared for the Greater Lake Washington Steering Committee. Seattle, WA.

Grothkopp, F. 1997. University Regulator post CSO separation study. King County Metropolitan Services, Seattle, WA.

King County 7–3 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Harader, Jr., R.R., and G.H. Allen. 1983. Ammonia toxicity to Chinook salmon parr: Reduction in saline water. Transactions of the American Fisheries Society 112: 834−837.

Hart Crowser. 1992. Sediment monitoring program results. Prepared for Lake Union Drydock Company, Seattle, WA.

Hart Crowser. 2014a. Interim Action Work Plan, Jacobson Terminals Property, Seattle, Washington. Prepared for Washington State Department of Ecology. Seattle, WA.

Hart Crowser. 2014b. Sandblast grit removal, interim remedial action, Northlake Shipyard site, Seattle, Washington. Prepared for Washington State Department of Ecology, Seattle, WA.

Hecky, R.E., and P. Kilham. 1988. Nutrient limitation of phytoplankton in freshwater and marine environments: A review of recent evidence on the effects of enrichment. Limnology and Oceanography 33: 796−822.

Helsel, D.R. 2005a. More than obvious: Better methods for interpreting nondetect data. Environmental Science & Technology 39: 419A−423A.

Helsel, D.R. 2005b. Nondetects and data analysis: Statistics for censored environmental data. John Wiley & Sons, Inc. Hoboken, NJ. Pp 63−68.

Helsel, D.R., and R.M. Hirsch. 2002. Statistical methods in water resources techniques of water resources investigations, Book 4, Chapter A3. U.S. Geological Survey. 522 pages.

Herrera. 2003. Green Lake integrated phosphorus management plan. Prepared for City of Seattle Department of Parks and Recreation by Herrera Environmental Consultants, Seattle, WA.

Herrera & Brown and Caldwell. 1994. Lake Union water quality/environmental assessment project. Vol. 1, executive and technical summary; Vol. 2, project report; and Vol. 3, stormwater and basin maps. Herrera Environmental Consultants & Brown and Caldwell, Seattle, WA.

Hileman, J., J. Yearsley, and J. Anderson. 1985. Lake Union sediment investigation: Seattle, Washington, March 20–21, 1984. U.S. Environmental Protection Agency, Region 10, Seattle, WA.

Horthon T., K. Hornik, M.A. van de Wiel, and A. Zeileis. 2008. Implementing a class of permutation tests: The coin package. Journal of Statistical Software 28: 1−23.

King County 7–4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Jassby, A.D., J.E. Reuter, R.P. Axler, C.R. Goldman, and S.H. Hackley. 1994. Atmospheric deposition of nitrogen and phosphorus in the annual nutrient load of Lake Tahoe (California‐Nevada). Water Resources Research 30: 2207−2216.

Jacobs, L., R. Barrick, and T. Ginn. 1988. Application of a mathematical model (SEDCAM) to evaluate the effects of source control on sediment contamination in Commencement Bay. In Proceedings: First Annual Meeting on Puget Sound Research 2: 677−684.

Kaplan, E.L., and P. Meier. 1958. Nonparametric estimation from incomplete observations. Journal of the American Statistical Association 53: 457−481.

Kilham, S.S. 1986. Dynamics of Lake Michigan natural phytoplankton communities in continuous cultures along a Si:P loading gradient. Canadian Journal of Fisheries and Aquatic Sciences 43: 351−360.

King County. 2001. Lake Union sediment study sampling and analysis plan. King County, Department of Natural Resources and Parks, Modeling, Assessment, and Analysis Group, Seattle, WA.

King County. 2003a. Sammamish/Washington Analysis and Modeling Program. Lake Washington existing conditions report. Prepared by Tetra Tech ISG, Inc., and Parametrix, Inc., for King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, WA.

King County. 2003b. Sammamish/Washington Analysis and Modeling Program. Results of a human use survey for shoreline areas of Lake Union, Lake Washington, and Lake Sammamish. Prepared by Parametrix, Inc., for King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, WA.

King County. 2004a. A Sediment triad analysis of Lakes Sammamish, Washington, and Union. King County Department of Natural Resources and Parks, Science Section, Seattle, WA.

King County. 2004b. Major lakes phytoplankton study: Comparison of composite sampling techniques. Prepared by C. DeGasperi, King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, WA.

King County. 2011a. CSO sediment quality characterization: Final sampling and analysis plan. King County Department of Natural Resources and Parks, Wastewater Treatment Division, Seattle, WA.

King County. 2011b. Lake Washington/Cedar/Sammamish Watershed (WRIA 8) land cover change analysis. Prepared for WRIA8 Technical Committee by King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, Washington.

King County 7–5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

King County. 2012. 2012 King County long‐term combined sewer overflow control plan amendment. King County Department of Natural Resources and Parks, Wastewater Treatment Division, Seattle, WA.

King County. 2013. Estimating PCB and PBDE loadings to the Lake Washington watershed. Prepared for U.S. Environmental Protection Agency, Region 10, by R. Jack and J. Colton, King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, WA.

King County. 2016. Correction factors for freshwater dissolved and total nutrients for 1998 and 2006 instrument and method changes by the King County Environmental Laboratory. Prepared by Timothy Clark, King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, WA.

King County. Unpublished. Data collected from the Laboratory Information Management System for site KSQU01.

Kling, G.W., A.E. Giblin, B. Fry, and B.J. Peterson. 1991. The role of seasonal turnover in lake alkalinity dynamics. Limnology and Oceanography 36: 106−122.

Lee, L. 2013. NADA: Nondetects and data analysis for environmental data. R package version 1.5‐6. http://CRAN.R‐project.org/package=NADA.

Lenat, D. R. 1993. A biotic index for the southeastern United States: Derivation and list of tolerance values, with criteria for assigning water‐quality ratings. Journal of the North American Benthological Society 12: 279−290.

Lower Duwamish Waterway Group (LDWG). 2010. Lower Duwamish Waterway remedial investigation. Prepared by Windward Environmental, LLC, Seattle, WA.

Lower Duwamish Waterway Group (LDWG). 2011. Memorandum: Additional information on achieving the state standards in 10 years, upper subsurface contaminant concentration limit for use of enhanced natural recovery areas, and subsurface remaining graphics. Submitted to Washington State Department of Ecology. Olympia, WA.

Lower Duwamish Waterway Group (LDWG). 2013. LDWG Comments on Proposed Plan. Submitted to US Environmental Protection Agency. Seattle, WA.

Mantua, N.J., S.R. Hare, Y. Zhang, J.M. Wallace, and R.C. Francis. 1997. A Pacific interdecadal climate oscillation with impacts on salmon production. Bulletin of the American Meteorological Society 78: 1069−1079.

King County 7–6 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Metro. 1987. University regulator combined sewer overflow control predesign project: Water quality impact supplement. Municipality of Metropolitan Seattle, Seattle, WA.

Metro. 1993. Lake Union data compilation and review. Municipality of Metropolitan Seattle, Seattle, WA.

Newell, J.C., and T.P Quinn. 2005. Behavioral thermoregulation by maturing adult sockeye salmon (Onorhynchus nerka) in a stratified lake prior to spawning. Canadian Journal of Zoology 83: 1232−1239.

NOAA. 1994. Pacific Marine Center sediment survey. National Oceanographic and Atmospheric Administration, Seattle, WA.

Rattray, Jr., M., G.R. SeckeI, and C.A. Barnes. 1954. Salt budget in the Lake Washington Ship Canal system. Journal of Marine Research 13: 263−275.

RETEC. 2002. North Lake Union Phase 2 sediment investigation work plan. Prepared for Puget Sound Energy by The RETEC Group, Inc., Seattle, Washington.

Reynolds, G.L., and J. Hamilton Taylor. 1992. The role of planktonic algae in the cycling of Zn and Cu in a productive soft‐water lake. Limnology and Oceanography 37: 1759−1769.

Rogowski, D. 2000. Saltwater intrusion in Salmon Bay and Lake Union sediments. Washington State Department of Ecology, Olympia, WA.

Serdar, D., and J. Cubbage. 1996. Chemical contaminants in Salmon Bay sediments, results of Phase II sampling. Washington State Department of Ecology, Environmental Investigations and Laboratory Services Program, Olympia, WA.

Serdar, D., J. Cubbage, and D. Rogowski. 2000. Concentrations of chemical contaminants and bioassay response to sediments in Salmon Bay, Seattle. Washington State Department of Ecology, Environmental Assessment Program, Olympia, WA.

Shannon & Wilson, Inc. 2008. Shallow sediment characterization report. USACE 2005‐ 00969 Permit Conditions. Prepared for City of Seattle, Department of Parks and Recreation, Seattle, WA.

Srinivasan, M., and G.W. Swain. 2007. Managing the use of copper‐based antifouling paints. Environmental Management 39: 423−441.

Swain, E.B., D.R. Engstrom, M.E. Brigham, T.A. Henning, and P.L. Brezonik. 1992. Increasing rates of atmospheric mercury deposition in midcontinental North America. Science 257: 784−787.

King County 7–7 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Tilman, D., S.S. Kilham, and P. Kilham. 1982. Phytoplankton community ecology: The role of limiting nutrients. Annual Review of Ecology and Systematics 13: 349−372.

Tobin, C.C. 1986. Lake Union and Ship Canal historical use study. City of Seattle Land Use and Transportation Project, Seattle, WA.

Tomlinson, R.D., R.J. Morrice, E.C.S. Duffield, and R.I. Matsuda. 1977. A baseline study of the water quality, sediments, and biota of Lake Union. Municipality of Metropolitan Seattle, Seattle, WA.

Turney, G.L., and D.F. Goerlitz. 1990. Organic contamination of ground water at Gas Works Park, Seattle, Washington. Groundwater Monitoring and Remediation 10: 187−198.

University of Michigan. 2014. The global water and nitrogen cycles. http://www.globalchange.umich.edu/globalchange1/current/lectures/kling/water _nitro/water_and_nitrogen_cycles.htm. Accessed October 10, 2014.

USACE. 1990. Memorandum for record: Decision on suitability of dredged material tested under PSDDA criteria for the TriStar Marine Maintenance Dredging project (Oyb‐2‐ 013209) to be disposed of at the Elliott Bay open‐water disposal site. U.S. Army Corps of Engineers, Puget Sound Dredged Disposal Analysis Program, Seattle, WA.

USACE. 2004. Lake Washington Ship Canal water quality monitoring and analysis plan. U.S. Army Corps of Engineers, Seattle District, Hydrology and Hydraulics Section, Seattle, WA.

USACE. 2005a. Memorandum for record: Determination of the suitability of the post‐ dredge sediment surface quality relative to the Washington Department of Ecology’s antidegradation policy for the Lakeside Industries Sand and Gravel spill removal dredging (2003‐2‐00198) as evaluated under Section 404 of the Clean Water Act. U.S. Army Corps of Engineers, Dredged Material Management Program, Seattle, WA.

USACE. 2005b. Memorandum For Record: Determination Of The Suitability On Propsed Dredged Material Characterized From The Port Of Seattle Fishermen’s Terminal (2005‐00421) As Evaluated Under Section 404 Of The Clean Water Act For Unconfined‐Open‐Water Disposal. U.S. Army Corps of Engineers, Dredged Material Management Program. Seattle, WA.

USACE. 2010. Memorandum for record: Determination on the evaluation of sediment quality results required as special conditions to Corps permit (NWS‐2005‐00969‐ WRD) within MCTA cleanup footprint for South Lake Union Park as evaluated under Section 404 of the Clean Water Act. U.S. Army Corps of Engineers, Seattle District, Dredged Material Management Program, Seattle, WA.

King County 7–8 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

USACE. 2012a. Lake Washington Ship Canal Water Quality Science Panel final recommendations report. U.S. Army Corps of Engineers, Seattle District, Seattle, WA.

USACE. 2012b. Memorandum for record: Determination regarding the suitability/unsuitability of proposed dredged material from the Salmon Bay Marina for unconfined open‐water disposal at the Elliott Bay open‐water site. U.S. Army Corps of Engineers, Dredged Material Management Program, Seattle, WA.

WDFW. 2002. Salmonid stock inventory 2002 (SaSI). Washington Department of Fish and Wildlife.

WDFW. 2015. Salmon Conservation and reporting engine (SCoRE). Washington Department of Fish and Wildlife. http://wdfw.wa.gov/score.

Weitkamp, D., G. Ruggerone, L. Sacha, J. Howell, and B. Bachen. 2000. Factors affecting Chinook populations, background report. Prepared for the City of Seattle by Parametrix, Inc., Natural Resources Consultants, and Cedar River Associates.

Wenning, R.J., G.E. Batley, C.G. Ingersoll, and D.W. Moore (eds.). 2005. Use of sediment quality guidelines and related tools for the assessment of contaminated sediments. Proceedings of the Pellston Workshop, Fairmont, Montana, August 2002. Society of Environmental Toxicology and Chemistry, Pensacola, FL.

Wetzel, R.G. 2001. Limnology: Lake and river ecosystems. Academic Press, San Diego, CA.

Wildhaber, M.L., and C.J. Schmitt. 1998. Indices of benthic community tolerance in contaminated Great Lakes sediments: Relations with sediment contaminant concentrations, sediment toxicity, and the sediment quality triad. Environmental Monitoring and Assessment 49: 23−49.

Winslow, L., J. Read, R. Woolway, J. Brentrup, and J. Zwart . 2014. rLakeAnalyzer: Package for the analysis of lake physics. R package version 1.3. http://CRAN.R‐ project.org/package=rLakeAnalyzer.

Wooster, W.S., A.J. Lee, and G. Dietrich. 1969. Redefinition of salinity. Deep‐Sea Research 16: 321−322.

Yake, B., D. Norton, and M. Stinson. 1986. Application of the Triad approach to freshwater sediment assessment: An initial investigation of sediment quality near Gas Works Park, Lake Union. Washington State Department of Ecology, Olympia, WA.

Zalizniak, L., B.J. Kefford, and D. Nugegoda. 2006. Is all salinity the same? The effect of ionic compositions on the salinity tolerance of five species of freshwater invertebrates. Marine and Freshwater Research 57: 75−82.

King County 7–9 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Zisette, R.R. 1989. Lake Union sediment quality. Prepared for Seattle City Light by Parametrix, Inc., Seattle, WA.

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APPENDIX A: GLOSSARY aerobic Living in the presence of oxygen. algae Mostly aquatic, non-vascular organisms (eukaryotes and cyanobacteria) that float in the water or attach to larger plants, rocks, and other substrates. Also called phytoplankton when floating In the water, these individuals are usually visible only with a microscope. They are a normal and necessary component of aquatic life, but excessive numbers can make the water appear cloudy and colored, which may discourage human use. algal bloom Heavy growth of algae or cyanobacteria in and on a body of water, often a result of high nutrient concentrations when occurring frequently but blooms can also be a normal occurrence. Decomposition of algae following blooms can cause reductions in oxygen that may threaten fish and other aquatic animals. alkalinity Acid-neutralizing or buffering capacity of water. It is primarily a function of the carbonate, bicarbonate, and hydroxide content in water. The lower the alkalinity, the less capacity the water has to neutralize acids without lowering pH and becoming more acidic. ammonia (NH3) A nitrogen-containing substance that may indicate recently decomposed plant or animal material. anaerobic Living in the absence of oxygen. annelid Any member of the phylum Annelida, a group of invertebrates. They are also called "ringed worms," which are segmented worms including ragworms, earthworms, and leeches. Various forms specialize in their respective ecosystems. They can be found in marine environments, fresh water, and moist terrestrial environments. anoxic No oxygen present in the system; see anaerobic.

Aroclors One of the most commonly known trade names for PCB mixtures. benthic Associated with the sediments of a water body; often used to describe the community of organisms (benthos) that live in or on the sediment. benthic See Invertebrates. invertebrates benthos The communities of aquatic life that dwell in or on the bottom sediments of a water body. bioaccumulation Accumulation of chemicals in the tissue of organisms through any route, including respiration, ingestion, and direct contact with contaminated water, sediment, and pore water in the sediment. blank Artificially introduced contamination. Blank contamination (chemical demonstrated contamination as present when it should not be) of a sample indicates that other samples analyzed in the same batch may possess false positives. chlorophyll A green pigment found in organisms that make their own food, including algae. It plays an important part in the chemical reactions of photosynthesis. A

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measurement of chlorophyll a (one form of chlorophyll) is commonly used to estimate the abundance of phytoplankton in water. combined sewer Discharges of combined sewage and stormwater into water bodies from regulated overflow (CSO) locations as the result of heavy storms. These discharges are designed to relieve the sewer system as it becomes overloaded with normal sewer flow and increased stormwater runoff. concentration The amount of one substance in a given amount of another substance, such as the mass of a chemical in a liter of water. conductivity A measure of water's capacity to convey an electric current. It is related to the total amount of dissolved charged substances (ions) in the water. It can be used as one general indicator of water quality. It is often used as a surrogate for salinity measurements. congener Chemical substances (constituents) related to each other by origin, structure, or function. corrective action A hazardous waste site that is being investigated and cleaned up under the site Resource Conservation and Recovery Act (RCRA). The site may include risks comparable to Superfund sites. crustacean Any member of the subphylum Crustacea (phylum Arthropoda), a group of invertebrate animals. Crabs, lobsters, shrimps, and wood lice are among the best known crustaceans. degradate The product of degradation diatoms Golden-brown algae that make intricate siliceous shells, which are found in open water and attached to wood and rocks along shorelines. Diatoms are nutritious food for planktonic animals and are important components of a healthy food chain in aquatic systems. dinoflagellates Plankton usually having two flagella, one in a groove around the body and the other extending from its center. They perform photosynthesis, but many ingest phytoplankton as well. dissolved oxygen Oxygen that is dissolved in the water. Certain concentrations are necessary for (DO) the life processes of aquatic animals. The oxygen is supplied by the photosynthesis of plants, including algae, and by aeration through contact and mixing of the surface water with the atmosphere. Oxygen is consumed by aerobic organisms during respiration and by the oxidation of chemicals. eelgrass A vascular, flowering plant found in shallow muddy or sandy habitats that spreads by an underground stem. ecosystem Any complex of living organisms, along with the non-living factors that affect them and are affected by them. Includes plants, animals, the nutrients that sustain them, and all of the other environmental conditions necessary for successful maturation and reproduction. effluent Liquids discharged from sewage treatment plants, septic systems, industries, or stormwater sources to surface waters. endocrine Chemicals that may interfere with an animal’s endocrine system and produce disrupting adverse developmental, reproductive, neurological, and immune effects. A wide

King County A‐2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal compounds range of substances, both natural and manmade, are thought to cause endocrine disruption, including pharmaceuticals, dioxins and dioxin-like compounds, PCBs, pesticides, and plasticizers. Endocrine disruptors may be found in many everyday products, including plastic bottles, metal food cans, detergents, flame retardants, food, toys, and cosmetics. epilimnion Top-most layer in a thermally stratified lake. estuary A partly enclosed coastal body of brackish water with one or more rivers or streams flowing into it and with a free connection to the open sea/ocean. eutrophic Waters in which phytoplankton are able to maintain large populations; generally related to nutrient supply. eutrophication The physical, chemical, and biological changes associated with enrichment of a water body from increases in nutrients. fecal coliform A group of bacteria from the intestines of warm-blooded animals. Most of the bacteria bacteria are not harmful, but they are measured or counted as indicators of the possible presence of harmful bacteria. groundwater Water located and moving beneath the surface of the earth. The water in the ground is supplied by the seepage (percolation) of rainwater, snowmelt, and other surface water into the soil. Some groundwater may be found far beneath the earth’s surface; other groundwater may be only a few inches from the surface.

Hydrolab® A handheld instrument for monitoring multiple water quality parameters. hypolimnion Bottom layer of water in a thermally stratified lake. hypoxic Low in oxygen; a condition that can be detrimental to aquatic organisms. imputation Replacing missing data with substituted values. Discarding any case that has a missing value may introduce bias or affect the representativeness of the results. Imputation preserves all cases by replacing missing data with a probable value based on other available information. Once all missing values have been imputed, the dataset can then be analyzed using standard techniques for complete data. intertidal zone The area between the high tide and low tide marks. infauna Aquatic animals living in the sediments of the sea floor. invertebrates Animals without internal skeletons including insects, crabs, bivalves, and worms. Benthic invertebrates are an important link in the food chain for fish and can be used as an indicator of sediment quality. left-censored A dataset with data points below known values, but it is unknown by how much. limiting nutrient The nutrient that is in lowest supply relative to demand. The limiting nutrient will be the one that is exhausted first by algae/phytoplankton growth. Increasing the amount of the limiting nutrient will result in increased algal production; once the limiting nutrient is exhausted, growth stops. lipid Any of a class of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents. They include many natural oils, waxes, and steroids.

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loading The total amount of material (sediments, nutrients, chemicals) entering a water body via streams, overland flow, precipitation, direct discharge, or other means over time (usually considered annually). method detection The minimum concentration that can be measured and reported with 99 percent limit (MDL) confidence that the concentration is greater than zero. molluscs A group of invertebrates that includes squids, octopuses, cuttlefishes, nudibranchs, snails, slugs, limpets, mussels, and many more.

Noctiluca Also known as sea sparkle, a genus of large dinoflagellates that live near the surface of the ocean and feed on other planktonic organisms.

Nephelometric A unit measuring the clarity of water. Turbidity Unit (NTU) nitrate, nitrite (NO3, Two types of nitrogen compounds. These nutrients are forms of nitrogen that NO2) algae may use for growth. nitrogen One of the elements essential for the growth of organisms. Nitrogen is most abundant on the earth in the form of N2 (nitrogen gas), comprising nearly 80 percent of the atmosphere, but this inert gas is not bioavailable to most organisms. Nitrogen is usually taken up by plants in the forms NO3, NO2, and NH3 (ammonia). non-ionized/ Electrically neutral atoms or molecules that have not been converted to electrically unionized charged atoms or molecules (ions). nonpoint source Pollution from diverse sources that are difficult to pinpoint as separate sources pollution and thus are more complicated to control or manage. Examples include area-wide erosion (as opposed to landslides or mass wasting), widespread failure of septic systems, certain farming practices or forestry practices, and residential/urban land uses (such as fertilizing lawns or landscaping). nutrient A chemical element, ion, or compound required by an organism for growth and reproduction. oceanographic A framework with 12 to 36 sampling bottles clustered around a central cylinder, rosette where a CTD (conductivity, temperature, and depth) or other sensor package can be attached. outfall A pipe that discharges effluent, CSOs, stormwater, and other substances to a receiving water body. pathogen A microorganism that can cause disease in other organisms. Pathogens include bacteria, viruses, fungi, and parasites found in sewage, in runoff from farms or city streets, and in water used for swimming. They can be present in municipal, industrial, and nonpoint source discharges. pH The log10- transformation of the activity of the hydrogen ion in solution. pH values less than 7 are acidic; values greater than 7 are basic. pH influences the speciation of metals and other constituents. Biota may be negatively impacted at very high and low pH values.

King County A‐4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal phthalates A group of chemicals used to make plastics more flexible and harder to break. (plasticizers) They are often called plasticizers. Some phthalates are used as solvents (dissolving agents) for other materials. They are used in hundreds of products, such as vinyl flooring, adhesives, detergents, lubricating oils, automotive plastics, plastic clothes (raincoats), and personal-care products (soaps, shampoos, hair sprays, and nail polishes). Phthalates are used widely in polyvinyl chloride plastics, which are used to make products such as plastic packaging film and sheets, garden hoses, inflatable toys, blood-storage containers, medical tubing, and some children's toys. phosphorus One of the essential nutrients for the growth of organisms. Phosphorus occurs naturally in soils and in organic material. photosynthesis The production of organic matter from inorganic carbon and water using the energy of light. In general, plants are equipped to carry out this process, while animals cannot. phytoplankton Free-floating microscopic organisms that photosynthesize (includes both algae and cyanobacteria). point source An input of pollutants into a water body from discrete sources, such as municipal pollution or industrial outfall pipes. polybrominated A class of persistent and bioaccumulative halogenated compounds that have diphenyl ethers emerged as a major environmental pollutant. PBDEs are used as flame-retardants (PBDEs) and are found in consumer goods such as electrical equipment, construction materials, coatings, textiles, and polyurethane foam (furniture padding). Similar in structure to polychlorinated biphenyls (PCBs), PBDEs resist degradation in the environment. polychlorinated Part of a broad family of manmade organic chemicals known as chlorinated biphenyls (PCBs) hydrocarbons. PCBs were domestically manufactured from 1929 until their manufacture was banned in 1979. They have a range of toxicity and vary in consistency from thin light-colored liquids to yellow or black waxy solids. Because of their non-flammability, chemical stability, high boiling point, and electrical insulating properties, PCBs were used in hundreds of industrial and commercial applications including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics, and rubber products; and in pigments, dyes, and carbonless copy paper. polycyclic aromatic A group of over 100 different chemicals that are formed during the incomplete hydrocarbons burning of coal, oil, gas, garbage, and other organic substances like tobacco or (PAHs) charbroiled meat. PAHs are usually found as a mixture containing two or more of these compounds, such as soot. Some PAHs are manufactured. These pure PAHs usually exist as colorless, white, or pale yellow-green solids. PAHs are found in coal tar, crude oil, creosote, and roofing tar, but a few are used in medicines or to make dyes, plastics, and pesticides. primary treatment The first stage of wastewater treatment involving removal of debris and solids by screening and settling. precursor A chemical compound that participates in the chemical reaction that produces another compound.

King County A‐5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal riprap A foundation or sustaining wall of stones or chunks of concrete thrown together without order (as in deep water) or a layer of this or similar material on an embankment slope to prevent erosion. salinity Saltiness or dissolved salt content of a body of water. salmonids Fish belonging to the taxonomic family Salmonidae, including multiple species of salmon, trout, char, and whitefish. secondary Following primary treatment, bacteria are used to consume organic wastes in treatment sewage. The treated sewage is then disinfected and discharged through an outfall. Nutrient concentrations are not decreased with secondary treatment. sediment Solid material deposited in the bottom of a water body over time, carried in by wind and water, or produced by plants and animals. stormwater Water that is generated by rainfall and is often routed into municipal drain systems in urban environments. stratification A layering effect produced by the warming of the surface in many water bodies during summer. Upper waters are progressively warmed by the sun, and the deeper waters remain cold. Because of the difference in density (warmer water is lighter), the two layers remain separate from each other. Upper waters "float" on deeper waters and wind-induced mixing occurs only in the upper waters. Oxygen in the bottom waters may become depleted. substrate A surface on which an organism grows or is attached. surface water Water located near the interface of water and air. For this assessment, waters to 1-m depth were considered “surface.”

Superfund The name given to the federal environmental program established to address abandoned hazardous waste sites. It is also the name of the fund established by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended (CERCLA). It allows the U.S. Environmental Protection Agency (EPA) to clean up such sites and to compel responsible parties to perform cleanups or reimburse the government for EPA-lead cleanups. thermal A distinction in the layers of a water body caused by the change in water's density stratification with temperature thermocline A distinct layer in a large body of fluid in which temperature changes more rapidly with depth than it does in the layers above or below. It is the barrier between the epilimnion and hypolimnion. total suspended Particles, both mineral (clay and sand) and organic (algae and small pieces of solids (TSS) decomposed plant and animal material), that are suspended in water. toxic Causing death, disease, cancer, genetic mutations, or physical deformations in any organism or its offspring upon exposure, ingestion, inhalation, or assimilation. trophic level The feeding position in a food chain. Primary producers such as photosynthetic organisms like phytoplankton form the first trophic level; herbivores form the second trophic level; and carnivores form the third and fourth trophic levels.

King County A‐6 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal turbidity Cloudiness in water caused by the suspension of tiny particles (algae or detritus), commonly measured in NTUs.

Van Dorn sampler A water sampling device that allows collection of a water sample from a desired depth without contaminating the sample with water from other depths. van Veen sampler Stainless steel clamshell-like device used to extract sediment and/or benthic invertebrate samples from a 0.1-m2 area. wastewater Water from sinks, toilets, and other sources in homes, industries, and businesses that is conveyed to wastewater treatment plants. Also called sewage. water column Water between the surface and the bottom sediments. Multiple depths at a given site are often sampled so that conditions can be described across the vertical distance between the surface and bottom. watershed The surrounding geographical area that contributes surface water and groundwater flow to a stream, lake, or other body of water. Also referred to as a “catchment basin” or “drainage basin.” zooplankton A diverse group of small animals that are found in water bodies of low to moderate flow, such as lakes, river estuaries, and bays. They are free swimming but typically have limited powers of locomotion. They feed on bacteria, algae, smaller animals, and/or organic detritus present in the water.

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APPENDIX B: STUDY AREA

Figure B-1. 1936 and 2011 aerial photographs of Salmon Bay.

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Figure B-2. 1936 and 2011 aerial photographs of Lake Union.

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Figure B-3. 1936 and 2011 aerial photographs of Portage Bay.

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Figure B-4. Opening of the Montlake Cut (Courtesy of MOHAI).

Figure B-5. Major features of the Hiram M. Chittenden Locks.

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Figure B-4. Lake Union/Ship Canal bathymetry with 1 m contour intervals. King County B‐5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure B-5. Lake Union/Ship Canal as the outlet of the Ceder-Sammamish watershed. King County B‐6 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

APPENDIX C: WATER QUALITY

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Figures

Figure C‐1. ACOE stations that continuously monitor salinity, conductivity, and temperature...... C‐4 Figure C‐2. (a) Boxplot of temperature data for 1 m (white) and 14 m (grey) depth at the Dexter long‐term monitoring site 2004‐2013 and (b) Boxplot of temperature difference between 1 m and 14 m depths. Negative differences in November due to saltwater wedge...... C‐7 Figure C‐3. (a) Boxplot of temperature data for 1 m (white) and 14 m (grey) depth at the Dexter long‐term monitoring site 1985‐1995 and( b) Boxplot of temperature difference between 1 m and 14 m depths. Negative differences in November due to saltwater wedge...... C‐9 Figure C‐4. Salinity by month at ACOE monitoring sites 2004‐2013 in order of westernmost to easternmost...... C‐10 Figure C‐5. Salinity concentrations at Dexter in Lake Union during (a) 2001 and 2002 on left and (b) 2002 and 2003 during the saltwater intrusion...... C‐11 Figure C‐6. Secchi transparency depths 2009‐2013. All sites combined...... C‐14 Figure C‐7. Time‐depth isopleths of (a) TSS and (b) turbidity at Dexter in Lake Union using median 2009‐2013 and 2004‐2008 values, respectively...... C‐15 Figure C‐8. Time‐depth isopleths of (a) pH and (b) alkalinity at Dexter in Lake Union. Median values from 2009‐2013 used...... C‐17 Figure C‐9. Annual summary of epilimnetic alkalinity concentrations at Dexter in Lake Union...... C‐20 Figure C‐10. Time‐depth isopleths of chlorophyll a at Dexter in Lake Union. Median 2006‐2009 Hydrolab® data used...... C‐21 Figure C‐11. Spring shallow water composite chlorophyll a concentrations at Dexter in Lake Union...... C‐22 Figure C‐12. Summer shallow water composite chlorophyll a concentrations at Dexter in Lake Union...... C‐22 Figure C‐13. Silica concentrations at all sites 2002‐2013. Note only Dexter was sampled from 2002 to 2008. The Locks and Montlake sites sampled beginning in 2009...... C‐30 Figure C‐14. Epilimnetic N:P ratio in the (a) spring and (b) summer at Dexter in Lake Union...... C‐31 Figure C‐15. Sampling locations for organic compounds...... C‐33 Figure C‐16. Epilimnetic concentrations of caffeine and dimethyl phthalate at Locks, Dexter, and Montlake...... C‐34

King County C‐2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Tables

Table C‐1. Seasonal Mann‐Kendall trends for fecal coliform bacteria...... C‐5 Table C‐2. Fecal Coliform concentrations correlations with rainfall, TSS, and turbidity. Spearman's Correlation Coefficients and (p‐values) reported...... C‐6 Table C‐3. Temperature trends determined through multivariate regression...... C‐8 Table C‐4. Seasonal Mann‐Kendall trends for volume‐weighted conductivity...... C‐12 Table C‐5. Seasonal Mann‐Kendall trends for volume‐weighted dissolved oxygen...... C‐13 Table C‐6. Seasonal Mann‐Kendall trends for Secchi transparency...... C‐16 Table C‐7. Seasonal Mann‐Kendall trends for pH...... C‐18 Table C‐8. Seasonal Mann‐Kendall trends for volume‐weighted alkalinity...... C‐19 Table C‐9. Seasonal Mann Kendall trends for shallow chlorophyll a concentrations ...... C‐22 Table C‐10. Seasonal Mann‐Kendall trends for volume‐weighted nitrate/nitrite. Interquartile ranges for p‐values and slope magnitude from 1000 permutations presented...... C‐24 Table C‐11. Seasonal Mann‐Kendall trends for volume‐weighted ammonia. Interquartile ranges for p‐values and slope magnitude from 1000 permutations presented...... C‐25 Table C‐12. Seasonal Mann‐Kendall trends for volume‐weighted total nitrogen...... C‐27 Table C‐13. Seasonal Mann‐Kendall trends for volume‐weighted orthophosphate. Interquartile ranges for p‐values and slope magnitude from 1000 permutations presented...... C‐28 Table C‐14. Seasonal Mann‐Kendall trends for volume‐weighted total phosphorus...... C‐29 Table C‐15. Summary statistics for metal water quality acute and chronic standards for Lake Union/Ship Canal. All values in µg/L. Standards compared to observed dissolved metal concentrations, except for the standard for Chromium‐III, which was compared to observed total chromium concentrations...... C‐32

King County C‐3 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure C-1. ACOE stations that continuously monitor salinity, conductivity, and temperature.

King County C‐4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Bacteria

Table C-1. Seasonal Mann-Kendall trends for fecal coliform bacteria. Years Magnitude Season Site Direction Significance p-value Evaluated (CFU/100mL/yr) Locks 1976-2013 ↓ *** <0.0001 -1.87 Fremont 1992-2008 ‐‐ n.s. 0.7592 -0.56 Summer Dexter 1984-2013 ↓ *** 0.0089 -0.89 I-5 Bridge 1992-2008 ‐‐ n.s. 0.3552 -0.88 Montlake 1984-2013 ↓ *** <0.0001 -1.00 Locks 1976-2013 ↓ *** 0.0049 -4.27 Fremont 1992-2008 ‐‐ n.s. 0.1130 -2.30 Fall Dexter 1984-2013 ↓ ** 0.0175 -1.37 I-5 Bridge 1992-2008 ↓ *** 0.0031 -2.91 Montlake 1984-2013 ↓ *** <0.0001 -4.24 Locks 1976-2013 ↓ * 0.0578 -2.13 Fremont 1992-2008 ‐‐ n.s. 0.1192 -0.78 Winter Dexter 1984-2013 ↓ *** 0.0013 -1.69 I-5 Bridge 1992-2008 ↓ ** 0.0344 -2.24 Montlake 1984-2013 ↓ *** <0.0001 -2.50 Locks 1976-2013 ↓ *** 0.0066 -0.92 Fremont 1992-2008 ‐‐ n.s. 0.2412 -0.67 Spring Dexter 1984-2013 ↓ *** <0.0001 -0.70 I-5 Bridge 1992-2008 ‐‐ n.s. 0.3710 -0.79 Montlake 1984-2013 ↓ *** <0.0001 -0.53 Locks 1976-2013 ↓ *** <0.0001 -1.60 Fremont 1992-2008 ↓ ** 0.0497 -1.00 All Year Dexter 1984-2013 ↓ *** <0.0001 -1.02 I-5 Bridge 1992-2008 ↓ *** <0.0001 -1.57 Montlake 1984-2013 ↓ *** <0.0001 -0.62

Bacteria, Rainfall, Suspended Solids, and Phytoplankton Correlations

The correlation between three‐day cumulative rainfall and fecal coliform concentrations were positive and highly significant for all sites, except at the I‐5 Bridge site, from 2004 to

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2013; the Locks and Fremont sites showed the highest correlation, and I‐5 Bridge showed the lowest (Table C‐2).

Correlation between fecal coliform concentrations and total suspended solids (TSS) during the past five years was significant at the Locks, Dexter, and Montlake sites (p<0.0487) with a Spearman’s correlation coefficients of ‐0.149411. Locks and Montlake fecal coliform values were negatively correlated with TSS, as well (Table C‐2). While counter‐intuitive, this relationship may be partially explained by the low values of TSS (max=5.0 mg/L) that do not reflect the influx of sediment from stormwater; vis‐à‐vis TSS was negatively correlated with rainfall (Spearman’s correlation coefficient = ‐0.1334, p<0.0001). Instead, TSS was positively correlated with phytoplankton biovolume at the Dexter site in Lake Union from 2003‐2013 (Spearman’s correlation coefficient = 0.2152, p=0.0030). Turbidity, on the other hand, is positively correlated with rainfall (Spearman’s correlation coefficient = 0.1982, p=0.0003) and reflects in the introduction of stormwater carrying fine particulate matter.

While wet‐weather events flush and dilute suspended solids, such as phytoplankton, from the water column, these events also introduce fecal coliform bacteria; phytoplankton biovolume and fecal bacteria were slightly significantly negatively correlated at site Dexter (Table C‐2). This negative correlation can also be explained by the seasonality of phytoplankton biovolumes (greater in the spring and summer due to high light availability and adequate temperature) and wet‐weather events (greater in fall, winter, and spring).

Table C-2. Fecal Coliform concentrations correlations with rainfall, TSS, and turbidity. Spearman's Correlation Coefficients and (p-values) reported. Three-Day Rainfall TSS Turbidity Biovolume Site (2004-2013) (2009-2013) (2003-2008) (2003-2013) 0.4013 -0.1966 0.0957 Locks NA (<0.0001) (0.0487) (0.4078) 0.4260 0.0714 Fremont NA NA (0.0003) (0.5538) 0.3573 -0.3113 0.01945 -0.1394 Dexter (<0.0001) (0.0015) (0.8711) (0.0564) 0.1330 0.1088 I-5 Bridge NA NA (0.2394) (0.3128) 0.3543 -0.3237 -0.1088 Montlake NA (<0.0001) (0.0010) (0.3100)

11 Only Locks, Dexter, and Montlake had corresponding TSS values. Locks and Montlake had TSS values from 2009‐2013, and Dexter had values from 2003‐2013. For 2009‐2013, 23.8% of TSS values were below the MDL.

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Physical Parameters

Temperature

Figure C-2. (a) Boxplot of temperature data for 1 m (white) and 14 m (grey) depth at the Dexter long-term monitoring site 2004-2013 and (b) Boxplot of temperature difference between 1 m and 14 m depths. Negative differences in November due to saltwater wedge.

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Table C-3. Temperature trends determined through multivariate regression. Years Magnitude Season Site Depth Direction Significance p-value Evaluated (°C/yr) Locks All 1986-2013 ↑ *** 0.0018 0.064 Fremont All 1986-2008 ‐‐ n.s. 0.5235 0.017 0-5m 1985-2013 ‐‐ n.s. 0.5083 0.014 Dexter 10- Summer 1985-2013 *** <0.0001 -0.111 15m ↓ I-5 All 1986-2008 n.s. 0.3217 0.028 Bridge ‐‐ Montlake All 1986-2013 ↑ * 0.0753 0.040 Locks All 1986-2013 ‐‐ n.s. 0.8969 -0.003 Fremont All 1986-2008 ‐‐ n.s. 0.7129 -0.013 0-5m 1985-2013 ‐‐ n.s. 0.8890 -0.004 Dexter 10- Fall 1985-2013 n.s. 0.7182 -0.009 15m ‐‐ I-5 All 1986-2008 n.s. 0.6978 -0.013 Bridge ‐‐ Montlake All 1986-2013 ‐‐ n.s. 0.4737 -0.016 Locks All 1986-2013 ↑ *** 0.0054 0.063 Fremont All 1986-2008 ‐‐ n.s. 0.8342 0.006 0-5m 1985-2013 ↑ *** 0.0018 0.057 Dexter 10- Winter 1985-2013 *** 0.0004 0.054 15m ↑ I-5 All 1986-2008 n.s. 0.7264 -0.010 Bridge ‐‐ Montlake All 1986-2013 ↑ *** 0.0004 0.055 Locks All 1986-2013 ↑ ** 0.0355 0.043 Fremont All 1986-2008 ‐‐ n.s. 0.4683 -0.040 0-5m 1985-2013 ↑ * 0.0669 0.040 Dexter 10- Spring 1985-2013 n.s. 0.7077 0.005 15m ‐‐ I-5 All 1986-2008 n.s. 0.6631 -0.026 Bridge ‐‐ Montlake All 1986-2013 ‐‐ n.s. 0.2956 0.023 Locks All 1986-2013 ↑ *** 0.0006 0.044 Fremont All 1986-2008 ‐‐ n.s. 0.8318 0.005 0-5m 1985-2013 ↑ ** 0.0330 0.029 Dexter 10- All Year 1985-2013 n.s. 0.4377 -0.011 15m ‐‐ I-5 All 1986-2008 n.s. 0.8420 0.045 Bridge ‐‐ Montlake All 1986-2013 ↑ * 0.0761 0.023

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Figure C-3. (a) Boxplot of temperature data for 1 m (white) and 14 m (grey) depth at the Dexter long-term monitoring site 1985-1995 and ( b) Boxplot of temperature difference between 1 m and 14 m depths. Negative differences in November due to saltwater wedge.

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Salinity

Figure C-4. Salinity by month at ACOE monitoring sites 2004-2013 in order of westernmost to easternmost. White boxes represent 5.5, 3.4, 5,5, 1.2, and 1.8 m and grey boxes represent 12.8, 9.8, 12.2, 11.0, and 10.7 m at LLLW, BBLW, FBLW, GWLW, and UBLW, respectively. Sample size shown below respective boxes. Dashed line represents the minimum salinity defining saltwater (30 ppt).

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a b

Figure C-5. Salinity concentrations at Dexter in Lake Union during (a) 2001 and 2002 on left and (b) 2002 and 2003 during the saltwater intrusion.

King County C‐11 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table C-4. Seasonal Mann-Kendall trends for volume-weighted conductivity. Season Site Years Direction Significance p-value Magnitude Evaluated (uS/cm/yr) Locks 1976-2013 ‐‐ n.s. 0.4594 -3.87 Fremont 1974-2008 ‐‐ n.s. 0.8676 2.10 Summer Dexter 1986-2013 n.s. 0.2934 8.52 ‐‐ I-5 Bridge 1986-2008 ‐‐ n.s 0.2786 0.10 Montlake 1986-2013 ‐‐ n.s. 0.7611 -0.11 Locks 1976-2013 ‐‐ n.s. 0.3147 -5.95 Fremont 1974-2008 ↑ ** 0.0274 1.68 Fall Dexter 1986-2013 ↑ * 0.0946 1.61

I-5 Bridge 1986-2008 ‐‐ n.s. 0.7074 0.10 Montlake 1986-2013 ‐‐ n.s. 0.6121 -0.08 Locks 1976-2013 ‐‐ n.s 0.2417 -0.69 Fremont 1974-2008 ‐‐ n.s. 0.6051 0.12 Winter Dexter 1986-2013 ‐‐ n.s. 0.8601 -0.04 I-5 Bridge 1986-2008 ‐‐ n.s. 0.3604 0.13 Montlake 1986-2013 ‐‐ n.s. 0.3120 0.30 Locks 1976-2013 ↓ ** 0.0314 -2.26 Fremont 1974-2008 ‐‐ n.s. 0.2817 0.20 Spring Dexter 1986-2013 ‐‐ n.s. 0.8701 0.08 I-5 Bridge 1986-2008 ‐‐ n.s. 0.3215 0.15 Montlake 1986-2013 ‐‐ n.s. 0.2882 0.17 Locks 1976-2013 ↓ ** 0.0325 -1.64 Fremont 1974-2008 ‐‐ n.s. 0.3672 0.25 All Year Dexter 1986-2013 ‐‐ n.s. 0.8615 0.06 I-5 Bridge 1986-2008 ‐‐ n.s. 0.5227 0.10 Montlake 1986-2013 ‐‐ n.s. 0.7539 0.03

King County C‐12 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Dissolved Oxygen Table C-5. Seasonal Mann-Kendall trends for volume-weighted dissolved oxygen. Years Magnitude Season Site Direction Significance p-value Evaluated (ppm/yr) Locks 1997-2013 ‐‐ n.s. 0.1762 -0.045 Fremont 1993-2008 ‐‐ n.s. 0.2365 -0.022 Summer Dexter 1993-2013 ‐‐ n.s. 0.9567 -0.004 I-5 Bridge 1993-2008 ↓ *** 0.0026 -0.077 Montlake 1997-2013 ↓ * 0.0570 -0.043 Locks 1997-2013 ‐‐ n.s. 0.2155 0.022 Fremont 1993-2008 ‐‐ n.s. 0.6285 0.011 Fall Dexter 1993-2013 ‐‐ n.s. 0.9385 -0.003 I-5 Bridge 1993-2008 ‐‐ n.s. 0.8913 -0.006 Montlake 1997-2013 ‐‐ n.s. 0.2979 -0.015 Locks 1997-2013 ‐‐ n.s. 0.1193 0.027 Fremont 1993-2008 ‐‐ n.s. 0.5114 0.009 Winter Dexter 1993-2013 ‐‐ n.s. 0.3742 0.005 I-5 Bridge 1993-2008 ‐‐ n.s. 0.6370 0.007 Montlake 1997-2013 ‐‐ n.s. 0.9661 0.000 Locks 1997-2013 ↓ * 0.0796 -0.068 Fremont 1993-2008 ‐‐ n.s. 0.1559 -0.077 Spring Dexter 1993-2013 ‐‐ n.s. 0.4101 -0.037 I-5 Bridge 1993-2008 ‐‐ n.s. 0.4870 -0.032 Montlake 1997-2013 ‐‐ n.s. 0.8572 -0.016 Locks 1997-2013 ‐‐ n.s. 0.6654 -0.005 Fremont 1993-2008 ‐‐ n.s. 0.9191 0.002 All Year Dexter 1993-2013 ‐‐ n.s. 0.2906 0.015 I-5 Bridge 1993-2008 ↓ *** 0.0057 -0.031 Montlake 1997-2013 ‐‐ n.s. 0.4627 -0.015

King County C‐13 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Turbidity / Total Suspended Solids / Secchi Transparency

Figure C-6. Secchi transparency depths 2009-2013. All sites combined.

King County C‐14 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure C-7. Time-depth isopleths of (a) TSS and (b) turbidity at Dexter in Lake Union using median 2009-2013 and 2004-2008 values, respectively.

King County C‐15 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table C-6. Seasonal Mann-Kendall trends for Secchi transparency. Years Magnitude Season Site Direction Significance p-value Evaluated (m/yr) Locks 1997-2013 ‐‐ n.s. 0.4545 0.015 Fremont 1986-2008 ↑ * 0.0624 0.057 Summer Dexter 1985-2013 ‐‐ n.s. 0.8144 -0.006 I-5 Bridge 1986-2008 ↑ *** 0.0087 0.083 Montlake 1997-2013 ‐‐ n.s. 0.8639 0.007 Locks 1997-2013 ‐‐ n.s. 0.3077 0.045 Fremont 1986-2008 ‐‐ n.s. 0.9923 0.010 Fall Dexter 1985-2013 ‐‐ n.s. 0.5885 -0.002 I-5 Bridge 1986-2008 ‐‐ n.s. 0.7264 0.023 Montlake 1997-2013 ‐‐ n.s. 0.4061 0.022 Locks 1997-2013 ‐‐ n.s. 0.4980 0.015 Fremont 1992-2008 ‐‐ n.s. 0.3537 0.055 Winter Dexter 1985-2013 ↑ ** 0.0153 0.027 I-5 Bridge 1992-2008 ↑ *** 0.0018 0.099 Montlake 1997-2013 ↑ * 0.0921 0.067 Locks 1997-2013 ‐‐ n.s. 0.8454 0.009 Fremont 1992-2008 ‐‐ n.s. 0.7172 0.027 Spring Dexter 1985-2013 ‐‐ n.s. 0.3293 -0.007 I-5 Bridge 1992-2008 ‐‐ n.s. 0.2911 0.029 Montlake 1997-2013 ‐‐ n.s. 0.7579 0.001 Locks 1997-2013 ‐‐ n.s. 0.1353 0.019 Fremont 1986-2008 ↑ * 0.0512 0.038 All Year Dexter 1985-2013 ‐‐ n.s. 0.4718 0.002 I-5 Bridge 1986-2008 ↑ *** 0.0049 0.057 Montlake 1997-2013 ‐‐ n.s. 0.1614 0.025

King County C‐16 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal pH and Alkalinity

Figure C-8. Time-depth isopleths of (a) pH and (b) alkalinity at Dexter in Lake Union. Median values from 2009-2013 used.

King County C‐17 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table C-7. Seasonal Mann-Kendall trends for pH.

Years Magnitude Site Direction Significance p-value Season Examined (units/yr) Locks 1992-2013 ‐‐ n.s. 0.6564 0.004 Fremont 1992-2008 ‐‐ n.s. 0.7133 0.005 Summer Dexter 1992-2013 ‐‐ n.s. 0.9500 0.000 I-5 Bridge 1992-2008 ‐‐ n.s. 0.1670 0.008 Montlake 1992-2013 ‐‐ n.s. 0.8328 -0.001 Locks 1992-2013 ‐‐ n.s. 0.3553 -0.007 Fremont 1992-2008 ↑ *** 0.0020 0.024 Fall Dexter 1992-2013 ↑ ** 0.0166 0.012 I-5 Bridge 1992-2008 ↑ ** 0.0423 0.021 Montlake 1992-2013 ‐‐ n.s. 0.4232 0.007 Locks 1992-2013 ↑ ** 0.0449 0.020 Fremont 1992-2008 ‐‐ n.s. 0.4193 0.012 Winter Dexter 1992-2013 ↑ ** 0.0278 0.012 I-5 Bridge 1992-2008 ↑ ** 0.0361 0.016 Montlake 1992-2013 ↑ *** 0.0002 0.026 Locks 1992-2013 ‐‐ n.s. 0.5687 -0.007 Fremont 1992-2008 ‐‐ n.s. 0.1621 -0.021 Spring Dexter 1992-2013 ‐‐ n.s. 0.1492 -0.006 I-5 Bridge 1992-2008 ‐‐ n.s. 0.9664 0.000 Montlake 1992-2013 ↑ ** 0.0347 0.020 Locks 1992-2013 ‐‐ n.s. 0.6685 0.002 Fremont 1992-2008 ‐‐ n.s. 0.2128 0.011 All Year Dexter 1992-2013 ↑ * 0.0899 0.007 I-5 Bridge 1992-2008 ↑ ** 0.0496 0.012 Montlake 1992-2013 ↑ ** 0.0291 0.010

King County C‐18 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table C-8. Seasonal Mann-Kendall trends for volume-weighted alkalinity. Magnitude Season Site Years Examined Direction Significance p-value (mg CaCO3/ L/yr) Locks 1997-2008 ↑ *** 0.0042 0.413 Fremont 1992-2008 ↑ ** 0.0848 0.200 Summer Dexter 1985-2013 ↑ *** 0.003 0.153 I-5 Bridge 1992-2008 ↑ * 0.0510 0.228 Montlake 1997-2008 ↑ ** 0.0125 0.403 Locks 1997-2008 ↑ * 0.0804 0.328 Fremont 1992-2008 ‐‐ n.s. 0.2477 0.106 Fall Dexter 1985-2013 ↑ * 0.0927 0.145 I-5 Bridge 1992-2008 ↑ * 0.0900 0.126 Montlake 1997-2008 ↑ ** 0.0320 0.463 Locks 1997-2008 ↑ *** 0.011 0.550 Fremont 1992-2008 ↑ ** 0.0150 0.279 Winter Dexter 1985-2013 ↑ *** <0.0001 0.184 I-5 Bridge 1992-2008 ↑ * 0.0516 0.137 Montlake 1997-2008 ↑ ** 0.0109 0.427 Locks 1997-2008 ↑ *** 0.0020 0.397 Fremont 1992-2008 ↑ ** 0.0372 0.183 Spring Dexter 1985-2013 ↑ *** 0.0001 0.180 I-5 Bridge 1992-2008 ↑ * 0.0940 0.194 Montlake 1997-2008 ↑ *** 0.0032 0.389 Locks 1997-2008 ↑ *** 0.0008 0.547 Fremont 1992-2008 ↑ ** 0.0468 0.191 All Year Dexter 1985-2013 ↑ ** 0.0113 0.129 I-5 Bridge 1992-2008 ↑ ** 0.0192 0.215 Montlake 1997-2008 ↑ *** 0.0010 0.509

King County C‐19 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure C-9. Annual summary of epilimnetic alkalinity concentrations at Dexter in Lake Union.

King County C‐20 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Chlorophyll a

Figure C-10. Time-depth isopleths of chlorophyll a at Dexter in Lake Union. Median 2006-2009 Hydrolab® data used.

King County C‐21 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure C-11. Spring shallow water composite chlorophyll a concentrations at Dexter in Lake Union.

Figure C-12. Summer shallow water composite chlorophyll a concentrations at Dexter in Lake Union.

King County C‐22 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table C-9. Seasonal Mann Kendall trends for shallow chlorophyll a concentrations Years Magnitude Season Site Direction Significance p-value Examined (µg/L/yr) Locks 1997-2013 ↓ ** 0.0460 -0.174 1986-2008 ‐‐ n.s. 0.7829 -0.019 Fremont 1997-2008 ↓ * 0.0570 -0.305 1985-2013 ↑ * 0.0508 0.062 Summer Dexter 1997-2013 ‐‐ n.s. 0.9087 0.035 I-5 1986-2008 ‐‐ n.s 0.5086 -0.045 Bridge 1997-2008 ↓ *** 0.0076 -0.184 Montlake 1997-2013 ‐‐ n.s. 0.7727 -0.011 Locks 1997-2013 ‐‐ n.s. 0.3917 -0.022 1986-2008 ↑ ** 0.0313 0.088 Fremont 1997-2008 ‐‐ n.s. 0.9916 -0.007 1985-2013 ‐‐ n.s. 0.1356 0.043 Fall Dexter 1997-2013 ‐‐ n.s. 0.4574 0.016

I-5 1986-2008 ‐‐ n.s. 0.1700 0.048 Bridge 1997-2008 ‐‐ n.s. 0.1564 -0.092 Montlake 1997-2013 ‐‐ n.s. 0.4897 -0.040 Locks 1997-2013 ‐‐ n.s 0.7118 0.057 1986-2008 ‐‐ n.s. 0.9372 -0.037 Fremont 1997-2008 ‐‐ n.s. 0.6901 0.171 1985-2013 ‐‐ n.s. 0.4655 0.017 Winter Dexter 1997-2013 ‐‐ n.s. 0.9490 -0.022

I-5 1986-2008 ‐‐ n.s. 0.9784 0.033 Bridge 1997-2008 ‐‐ n.s. 0.2246 0.184 Montlake 1997-2013 ‐‐ n.s. 0.7919 0.034 Locks 1997-2013 ↓ *** 0.0076 -0.300 1986-2008 ‐‐ n.s. 0.6459 -0.102 Fremont 1997-2008 ‐‐ n.s. 0.2764 -0.260 1985-2013 ‐‐ n.s. 0.9863 0.009 Spring Dexter 1997-2013 ↓ *** 0.0082 -0.352 I-5 1986-2008 ‐‐ n.s. 0.4706 -0.092 Bridge 1997-2008 ‐‐ n.s. 0.1350 -0.218 Montlake 1997-2013 ‐‐ n.s. 0.3450 -0.082 Locks 1997-2013 ↓ ** 0.0013 -0.105 All Year 1986-2008 ‐‐ n.s. 0.9999 0.003 Fremont 1997-2008 ↓ * 0.0635 -0.066

King County C‐23 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

1985-2013 ↑ * 0.0715 0.029 Dexter 1997-2013 ↓ ** 0.0349 -0.076 I-5 1986-2008 ‐‐ n.s. 0.9226 0.003 Bridge 1997-2008 ↓ * 0.0571 -0.088 Montlake 1997-2013 ‐‐ n.s. 0.1249 -0.029

Nutrients Nitrate/Nitrite Table C-10. Seasonal Mann-Kendall trends for volume-weighted nitrate/nitrite. Interquartile ranges for p-values and slope magnitude from 1000 permutations presented. Years Magnitude Season Site Direction Significance p-value Evaluated (ppb/yr) 0.1993 – -0.04 – Locks 1976-2013 ‐‐ n.s. 0.6306 -0.16 0.4149 – 0.03 – Fremont 1992-2008 ‐‐ n.s. 0.7946 0.23 0.2412 – -0.18 – Summer Dexter 1985-2013 ‐‐ n.s. 0.4591 -0.30 0.0201 – -0.26 – I-5 Bridge 1992-2008 ‐‐ n.s. 0.2125 -0.54 0.0126 – -0.13 – Montlake 1976-2013 ‐‐ n.s. 0.1234 -0.25 0.0041 – -1.61 – Locks 1976-2013 ↓ *** 0.0073 -1.68 0.4368 – -0.22 – Fremont 1992-2008 ‐‐ n.s. 0.6463 -0.47 0.1181 – -0.85 – Fall Dexter 1985-2013 ‐‐ n.s. 0.1780 -0.93 0.6317 – -0.30 – I-5 Bridge 1992-2008 ‐‐ n.s. 0.8652 -0.60 0.0141 – -1.43 – Montlake 1976-2013 ↓ ** 0.0234 -1.47 Locks 1976-2013 ↓ *** 0.0004 -2.62 Fremont 1992-2008 ‐‐ n.s. 0.4821 -1.32 Winter Dexter 1985-2013 ↓ * 0.0540 -2.27 I-5 Bridge 1992-2008 ‐‐ n.s. 0.8378 0.27 Montlake 1976-2013 ↓ *** 0.005 -1.98

King County C‐24 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

0.0009 – -2.10 – Locks 1976-2013 ↓ *** 0.0012 -2.16 0.4892 – -0.78 – Fremont 1992-2008 ‐‐ n.s. 0.6668 -1.11 Spring Dexter 1985-2013 ‐‐ n.s. 0.1192 -1.67 0.6668 – -0.79 – I-5 Bridge 1992-2008 ‐‐ n.s. 0.8040 -1.05 0.0057 – -1.93 – Montlake 1976-2013 ↓ *** 0.0082 -1.94 0.0003 – -0.99 – Locks 1976-2013 ↓ *** 0.0006 -1.04 0.1971- -0.80 – Fremont 1992-2008 ‐‐ n.s. 0.2680 -0.93 0.0111 – -0.90 – All Year Dexter 1985-2013 ↓ ** 0.0156 -0.96 0.0872 – -0.83 – I-5 Bridge 1992-2008 ‐‐ n.s 0.1616 -1.04 0.0001 – -0.93 – Montlake 1976-2013 ↓ *** 0.0002 -0.99

Ammonia Table C-11. Seasonal Mann-Kendall trends for volume-weighted ammonia. Interquartile ranges for p-values and slope magnitude from 1000 permutations presented. Years Magnitude v a Season Site Direction Significance p-value a t e d 0.1169 – -0.235 – Locks 1976-2013 ‐‐ n.s. 0.1762 -0.258 0.1041 – -0.633 – Fremont 1992-2008 ‐‐ n.s. 0.2059 -0.763 1.10 – Summer Dexter 1985-2013 ‐‐ n.s. 0.3354 1.20 0.0491 – -0.128 – I-5 Bridge 1992- 2008 ‐‐ n.s. 0.3251 -0.271 0.3823 – -0.006 – Montlake 1976-2013 ‐‐ n.s. 0.8115 -0.045

King County C‐25 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Locks 1976-2013 ↓ ** 0.0182 -0.524 Fremont 1992-2008 ↓ * 0.0902 -0.700 Fall Dexter 1985-2013 ‐‐ n.s. 0.3666 -0.417 I-5 Bridge 1992- 2008 ‐‐ n.s. 0.3330 -0.567 Montlake 1976-2013 ↓ *** 0.0041 -0.357 0.025 – -0.188 – Locks 1976-2013 ↓ * 0.0545 -0.218 0.2534 – -0.114 – Fremont 1992-2008 ‐‐ n.s. 0.4706 -0.177 0.0624 – -0.137 – Winter Dexter 1985-2013 ↓ * 0.1063 -0.158 0.7163 – 0.024 – I-5 Bridge 1992- 2008 ‐‐ n.s. 0.9371 0.138 0.2562 – -0.070 – Montlake 1976-2013 ‐‐ n.s. 0.4132 -0.092 0.0007 – -0.395 – Locks 1976-2013 ↓ *** 0.0017 -0.403 0.6849 – 0.036 – Fremont 1992-2008 n.s. ‐‐ 0.8921 0.104 0.01987 – -0.379 – Spring Dexter 1985-2013 ↓ ** 0.03434 -0.420 0.1272 – -0.185 – I-5 Bridge 1992- 2008 ‐‐ n.s. 0.3431 -0.303 0.0022 – -0.303 – Montlake 1976-2013 ↓ *** 0.0060 -0.320 0.0080 - -0.263 – Locks 1976-2013 ↓ *** 0.0014 -0.274 0.0185 – -0.407 – Fremont 1992-2008 ↓ ** 0.0276 -0.451 0.1038 – -0.209 – All Year Dexter 1985-2013 ‐‐ n.s. 0.1258 -0.222 0.0558 – -0.246 – I-5 Bridge 1992- 2008 ‐‐ n.s. 0.1229 -0.303 0.0092 – -0.104 – Montlake 1976-2013 ↓ ** 0.0216 -0.117

King County C‐26 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Total Nitrogen Table C-12. Seasonal Mann-Kendall trends for volume-weighted total nitrogen. Years Magnitude Season Site Direction Significance p-value Evaluated (ppb/yr) Locks 1993-2013 ↓ *** 0.0069 -4.75 Fremont 1993-2008 ‐‐ n.s. 0.3088 -2.32 Summer Dexter 1993-2013 ‐‐ n.s. 0.9140 -0.38 I-5 Bridge 1993-2008 ‐‐ n.s. 0.2520 -0.82 Montlake 1993-2013 ↓ ** 0.0217 -1.91 Locks 1993-2013 ↓ *** 0.0023 -4.55 Fremont 1993-2008 ↓ ** 0.0140 -3.79 Fall Dexter 1993-2013 ‐‐ n.s. 0.8823 -0.19 I-5 Bridge 1993-2008 ‐‐ n.s. 0.7413 0.59 Montlake 1993-2013 ↓ * 0.0691 -3.35 Locks 1993-2013 ↓ ** 0.0178 -7.13 Fremont 1993-2008 ‐‐ n.s. 0.2424 -3.26 Winter Dexter 1993-2013 ‐‐ n.s. 0.2165 -3.54 I-5 Bridge 1993-2008 ‐‐ n.s. 0.2659 -2.84 Montlake 1993-2013 ↓ ** 0.0221 -5.43 Locks 1993-2013 ‐‐ n.s. 0.1110 -3.59 Fremont 1993-2008 ‐‐ n.s. 0.2454 -0.66 Spring Dexter 1993-2013 ↓ * 0.0940 -2.56 I-5 Bridge 1993-2008 ‐‐ n.s. 0.2337 -3.24 Montlake 1993-2013 ↓ * 0.0555 -3.46 Locks 1993-2013 ↓ *** 0.0031 -4.20 Fremont 1993-2008 ‐‐ n.s. 0.1230 -2.81 All Year Dexter 1993-2013 ‐‐ n.s. 0.1113 -2.53 I-5 Bridge 1993-2008 ‐‐ n.s. 0.1961 -2.08 Montlake 1993-2013 ↓ ** 0.0129 -2.97

King County C‐27 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Phosphorus Table C-13. Seasonal Mann-Kendall trends for volume-weighted orthophosphate. Interquartile ranges for p-values and slope magnitude from 1000 permutations presented. Years Magnitude Season Site Direction Significance p-value Evaluated (ppb/yr) 0.0004 – -0.260 – Locks 1986-2013 ↓ *** 0.0032 -0.272 0.0034 – -0.374 – Fremont 1992-2008 ↓ *** 0.0065 -0.393 0.1920 – -0.597– Summer Dexter 1985-2013 ‐‐ n.s. 0.2082 -0.621 0.0050 – -0.144 – I-5 Bridge 1992 – 2008 ↓ ** 0.0372 -0.184 0.0253 – -0.028 – Montlake 1986-2013 ‐‐ n.s. 0.1875 -0.056 Locks 1986-2013 ↓ *** <0.0001 -0.491 -0.347 – Fremont 1992-2008 ↓ ** 0.0132 -0.358 Dexter 1985-2013 ** 0.0339 -0.333 Fall ↓ 0.0526 – -0.111 – I-5 Bridge 1992 – 2008 ‐‐ n.s. 0.1376 -0.146 0.0002 – -0.239 – Montlake 1986-2013 ↓ *** 0.0007 -0.250 0.0002 – -0.429 – Locks 1986-2013 ↓ *** 0.0003 -0.432 Fremont 1992-2008 ↓ ** 0.0135 -0.328 Winter 0.0022 – Dexter 1985-2013 *** -0.234 ↓ 0.0025 I-5 Bridge 1992 – 2008 ↓ *** 0.0039 -0.413 Montlake 1986-2013 ↓ *** 0.0001 -0.400 0.0103 – -0.035 – Locks 1986-2013 ↓ * 0.1012 -0.063 0.0547 – -0.200 – Fremont 1992-2008 ‐‐ n.s. 0.3799 -0.481 0.0010 – -0.050 – Spring Dexter 1985-2013 ↓ *** 0.0044 -0.061 0.0796 – -0.019 – I-5 Bridge 1992 – 2008 ‐‐ n.s. 0.4542 -0.048 0.0403 – -0.016 – Montlake 1986-2013 ‐‐ n.s. 0.3207 -0.037 -0.249 – All Year Locks 1986-2013 ↓ *** <0.0001 -0.255

King County C‐28 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

0.0005 – -0.274 – Fremont 1992-2008 ↓ *** 0.0009 -0.283 <0.0001 -0.200 – Dexter 1985-2013 ↓ *** – 0.0001 -0.206 0.0013 – -0.176 – I-5 Bridge 1992 – 2008 ↓ *** 0.0029 -0.191 <0.0001 -0.106 – Montlake 1986-2013 ↓ *** – 0.0001 -0.121

Table C-14. Seasonal Mann-Kendall trends for volume-weighted total phosphorus. Years Magnitude Season Site Direction Significance p-value Evaluated (ppb/yr) Locks 1986-2014 ‐‐ n.s. 0.9386 -0.032 Fremont 1992-2008 ↓ * 0.0592 -0.534 Summer Dexter 1985-2013 ‐‐ n.s. 0.1771 -1.23 I-5 Bridge 1992 – 2008 ‐‐ n.s. 0.1716 -0.229 Montlake 1986-2013 ‐‐ n.s. 0.5608 -0.049 Locks 1986-2014 ↓ *** 0.0001 -0.375 Fremont 1992-2008 ‐‐ n.s. 0.4790 -0.209 Fall Dexter 1985-2013 ‐‐ n.s. 0.6594 -0.108 I-5 Bridge 1992 – 2008 ‐‐ n.s. 0.9060 0.032 Montlake 1986-2013 ↓ * 0.0583 -0.154 Locks 1986-2014 ↓ *** 0.0006 -0.324 Fremont 1992-2008 ‐‐ n.s. 0.1188 -0.223 Winter Dexter 1985-2013 ↓ *** 0.0005 -0.228 I-5 Bridge 1992 – 2008 ‐‐ n.s. 0.1294 -0.301 Montlake 1986-2013 ↓ ** 0.0262 -0.199 Locks 1986-2014 ‐‐ n.s. 0.9993 0.000 Fremont 1992-2008 ‐‐ n.s. 0.5571 -0.097 Spring Dexter 1985-2013 ‐‐ n.s. 0.7908 -0.022 I-5 Bridge 1992 – 2008 ‐‐ n.s. 0.3318 -0.124 Montlake 1986-2013 ‐‐ n.s. 0.9287 -0.039 Locks 1986-2014 ↓ *** 0.0003 -0.200 Fremont 1992-2008 ↓ *** 0.0060 -0.270 All Year Dexter 1985-2013 ↓ *** 0.0083 -0.194 I-5 Bridge 1992 – 2008 ↓ *** 0.0060 -0.150 Montlake 1986-2013 ↓ *** 0.0008 -0.080

King County C‐29 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Silica

Figure C-13. Silica concentrations at all sites 2002-2013. Note only Dexter was sampled from 2002 to 2008. The Locks and Montlake sites sampled beginning in 2009.

King County C‐30 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Trophic State Indices and Limiting Factors

Figure C-14. Epilimnetic N:P ratio in the (a) spring and (b) summer at Dexter in Lake Union.

King County C‐31 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Metals

Table C-15. Summary statistics for metal water quality acute and chronic standards for Lake Union/Ship Canal. All values in µg/L. Standards compared to observed dissolved metal concentrations, except for the standard for Chromium-III, which was compared to observed total chromium concentrations. Parameter Acute Standard Chronic Standard Min Max Mean Median Min Max Mean Median Arsenic 360 190 Cadmium 1.01 34.9 1.48 1.27 0.43 4.75 0.54 0.50 Chromium-III 205 3000 268 245 66.6 972 86.8 83.9 Chromium -VI 15 10 Copper 5.49 120 7.53 6.74 4.07 66.7 5.38 4.90 Lead 17.1 559 25.25 21.81 0.67 21.9 0.98 0.85 Mercury 2.1 0.12 Nickel 513 8180 676 616 56.92 908 75.0 68.4 Selenium 20 5 Silver 0.44 122 1.06 0.64 Zinc 41.4 663 54.6 49.8 37.8 605 49.8 45.4

King County C‐32 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Organics

Figure C-15. Sampling locations for organic compounds.

King County C‐33 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Caffeine Dimethyl phthalate

Figure C-16. Epilimnetic concentrations of caffeine and dimethyl phthalate at Locks, Dexter, and Montlake.

King County C‐34 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

APPENDIX D: METALS AND ORGANICS

SUMMARY TABLES

King County D‐1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table D-1. Summary statistics for dissolved metals in Lake Union Ship Canal for 2000-2008. All values in µg/L. Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Locks Epi 4/30 3.3 9.8

King County D‐2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Epi 23/23 3.8 5.6 4.59 4.62 NA NA Dexter Hypo 36/36 3.77 39.4 4.72 6.85 NA NA 0527 Epi 4/4 4.17 4.19 4.17 4.18 NA NA 0535 Epi 2/2 3.8 3.82

King County D‐3 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL I-5 Bridge Epi 20/20 8640 9590 9130 9130 NA NA A535 Epi 2/2 8660 8720

King County D‐4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Montlake Epi 28/28 0.828 1.1 0.918 0.933 NA NA Locks Epi 33/33 35.7 72.6 43.7 48.1 NA NA Epi 29/29 35.2 55.9 39.3 40.4 NA NA Fremont Hypo 2/2 37 38.2

King County D‐5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL A535 Epi 2/2 3320 3350

King County D‐6 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL I-5 Bridge Epi 20/20 0.423 0.54 0.478 0.484 NA NA A535 Epi 2/2 0.44 0.5

King County D‐7 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Epi 2/25 0.011 0.017

King County D‐8 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table D-2. Summary statistics for totals metals in Lake Union Ship Canal 2000-2008. All values in µg/L. Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Locks Epi 33/33 7.2 34.1 17.5 18 NA NA Epi 29/29 2.5 31 8.4 9.71 NA NA Fremont Hypo 2/2 10.3 13.5

King County D‐9 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Locks Epi 4/33 0.01 0.01

King County D‐10 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Locks Epi 33/33 35.7 72.6 43.7 48.1 NA NA Epi 29/29 35.2 55.9 39.3 40.4 NA NA Fremont Hypo 2/2 37 38.2

King County D‐11 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL I-5 Bridge Epi 18/18 0.00042 0.00503 0.000629 0.000993 NA NA Montlake Epi 29/30 0.00022 0.00101 0.00042 5e-04 2e-04 2e-04 Locks Epi 33/33 0.257 0.444 0.309 0.321 NA NA Epi 29/29 0.257 0.352 0.281 0.29 NA NA Fremont Hypo 2/2 0.262 0.272

King County D‐12 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Locks Epi 3/3 6650 34200 6730 15900 NA NA Fremont Epi 3/3 4110 9470 4440 6010 NA NA Sodium Epi 3/3 4160 8890 4470 5840 NA NA Dexter Hypo 3/3 4290 170000 4720 59700 NA NA Montlake Epi 3/3 4120 4570 4390 4360 NA NA Locks Epi 2/33 0.036 0.039

King County D‐13 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table D-3. Summary statistics of detected organic compounds in Lake Union/Ship Canal for 2000-2004. All values in µg/L. Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Epi 0/31

King County D‐14 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Fremont Epi 0/2

King County D‐15 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL C535 Epi 2/2 0.599 0.685

King County D‐16 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Locks Epi 1/28 0.014 0.014

King County D‐17 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL C535 Epi 0/2

King County D‐18 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL 0535 Epi 0/2

King County D‐19 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Parameter Site Depth FOD Min Max Median Mean MinMDL MaxMDL Epi 0/5

King County D‐20 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

APPENDIX E: SEDIMENT QUALITY

Figures Tables Figure E‐1. Sediment concentration relative to the SCO criterion for ammonia in Lake Union/Ship Canal and Union Bay...... E‐5 Figure E‐2. Sediment concentration relative to the CSL criterion for ammonia in Lake Union/Ship Canal and Union Bay...... E‐6 Figure E‐3. Sediment concentration relative to the SCO criterion for total sulfides in Lake Union/Ship Canal and Union Bay...... E‐7 Figure E‐4. Sediment concentration relative to the CSL criterion for total sulfides in Lake Union/Ship Canal and Union Bay...... E‐8 Figure E‐5. Sediment concentration relative to the SCO criterion for arsenic in Lake Union/Ship Canal and Union Bay...... E‐9 Figure E‐6. Sediment concentration relative to the CSL criterion for arsenic in Lake Union/Ship Canal and Union Bay...... E‐10 Figure E‐7. Sediment concentration relative to the SCO criterion for cadmium in Lake Union/Ship Canal and Union Bay...... E‐11 Figure E‐8. Sediment concentration relative to the CSL criterion for cadmium in Lake Union/Ship Canal and Union Bay...... E‐12 Figure E‐9. Sediment concentration relative to the SCO criterion for chromium in Lake Union/Ship Canal and Union Bay...... E‐13 Figure E‐10. Sediment concentration relative to the CSL criterion for chromium in Lake Union/Ship Canal and Union Bay...... E‐14 Figure E‐11. Sediment concentration relative to the SCO criterion for copper in Lake Union/Ship Canal and Union Bay...... E‐15 Figure E‐12. Sediment concentration relative to the CSL criterion for copper in Lake Union/Ship Canal and Union Bay...... E‐16 Figure E‐13. Sediment concentration relative to the SCO criterion for lead in Lake Union/Ship Canal and Union Bay...... E‐17 Figure E‐14. Sediment concentration relative to the CSL criterion for lead in Lake Union/Ship Canal and Union Bay...... E‐18 Figure E‐15. Sediment concentration relative to the SCO criterion for mercury in Lake Union/Ship Canal and Union Bay...... E‐19 Figure E‐16. Sediment concentration relative to the CSL criterion for mercury in Lake Union/Ship Canal and Union Bay...... E‐20 Figure E‐17. Sediment concentration relative to the SCO criterion for nickel in Lake Union/Ship Canal and Union Bay...... E‐21

King County E‐1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E‐18. Sediment concentration relative to the CSL criterion for nickel in Lake Union/Ship Canal and Union Bay...... E‐22 Figure E‐19. Sediment concentration relative to the SCO criterion for selenium in Lake Union/Ship Canal and Union Bay...... E‐23 Figure E‐20. Sediment concentration relative to the CSL criterion for selenium in Lake Union/Ship Canal and Union Bay...... E‐24 Figure E‐21. Sediment concentration relative to the SCO criterion for silver in Lake Union/Ship Canal and Union Bay...... E‐25 Figure E‐22. Sediment concentration relative to the CSL criterion for silver in Lake Union/Ship Canal and Union Bay...... E‐26 Figure E‐23. Sediment concentration relative to the SCO criterion for zinc in Lake Union/Ship Canal and Union Bay...... E‐27 Figure E‐24. Sediment concentration relative to the CSL criterion for zinc in Lake Union/Ship Canal and Union Bay...... E‐28 Figure E‐25. Sediment concentration relative to the SCO criterion for bis(2‐ethylhexyl) phthalate in Lake Union/Ship Canal and Union Bay...... E‐29 Figure E‐26. Sediment concentration relative to the CSL criterion for bis(2‐ethylhexyl) phthalate in Lake Union/Ship Canal and Union Bay...... E‐30 Figure E‐27. Sediment concentration relative to the SCO criterion for beta‐ hexachlorocyclohexane in Lake Union/Ship Canal and Union Bay...... E‐31 Figure E‐28. Sediment concentration relative to the CSL criterion for beta‐ hexachlorocyclohexane in Lake Union/Ship Canal and Union Bay...... E‐32 Figure E‐29. Sediment concentration relative to the SCO criterion for carbazole in Lake Union/Ship Canal and Union Bay...... E‐33 Figure E‐30. Sediment concentration relative to the CSL criterion for carbazole in Lake Union/Ship Canal and Union Bay...... E‐34 Figure E‐31. Sediment concentration relative to the SCO criterion for dibenzofuran in Lake Union/Ship Canal and Union Bay...... E‐35 Figure E‐32. Sediment concentration relative to the CSL criterion for dibenzofuran in Lake Union/Ship Canal and Union Bay...... E‐36 Figure E‐33. Sediment concentration relative to the SCO criterion for dibutyltin in Lake Union/Ship Canal and Union Bay...... E‐37 Figure E‐34. Sediment concentration relative to the CSL criterion for dibutyltin in Lake Union/Ship Canal and Union Bay...... E‐38 Figure E‐35. Sediment concentration relative to the SCO criterion for dieldrin in Lake Union/Ship Canal and Union Bay...... E‐39 Figure E‐36. Sediment concentration relative to the CSL criterion for dieldrin in Lake Union/Ship Canal and Union Bay...... E‐40

King County E‐2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E‐37. Sediment concentration relative to the SCO criterion for di‐n‐butyl phthalate in Lake Union/Ship Canal and Union Bay...... E‐41 Figure E‐38. Sediment concentration relative to the CSL criterion for di‐n‐butyl phthalate in Lake Union/Ship Canal and Union Bay...... E‐42 Figure E‐39. Sediment concentration relative to the SCO criterion for di‐n‐octyl phthalate in Lake Union/Ship Canal and Union Bay...... E‐43 Figure E‐40. Sediment concentration relative to the CSL criterion for di‐n‐octyl phthalate in Lake Union/Ship Canal and Union Bay...... E‐44 Figure E‐41. Sediment concentration relative to the SCO criterion for endrin ketone in Lake Union/Ship Canal and Union Bay. Note: endrin ketone was not detected – values shown are MDL...... E ‐ 4 5 Figure E‐42. Sediment concentration relative to the CSL criterion for endrin ketone in Lake Union/Ship Canal and Union Bay. Note: endrin ketone was not detected – values shown are MDL...... E‐46 Figure E‐43. Sediment concentration relative to the SCO criterion for monobutyltin in Lake Union/Ship Canal and Union Bay...... E‐47 Figure E‐44. Sediment concentration relative to the CSL criterion for monobutyltin in Lake Union/Ship Canal and Union Bay...... E‐48 Figure E‐45. Sediment concentration relative to the SCO criterion for pentacholorphenol in Lake Union/Ship Canal and Union Bay...... E‐49 Figure E‐46. Sediment concentration relative to the CSL criterion for pentacholorphenol in Lake Union/Ship Canal and Union Bay...... E‐50 Figure E‐47. Sediment concentration relative to the SCO criterion for phenol in Lake Union/Ship Canal and Union Bay...... E‐51 Figure E‐48. Sediment concentration relative to the CSL criterion for phenol in Lake Union/Ship Canal and Union Bay...... E‐52 Figure E‐49. Sediment concentration relative to the SCO criterion for tetrabutyltin in Lake Union/Ship Canal and Union Bay...... E‐53 Figure E‐50. Sediment concentration relative to the CSL criterion for tetrabutyltin in Lake Union/Ship Canal and Union Bay...... E‐54 Figure E‐51. Sediment concentration relative to the SCO criterion for total PCBs in Lake Union/Ship Canal and Union Bay...... E‐55 Figure E‐52. Sediment concentration relative to the CSL criterion for total PCBs in Lake Union/Ship Canal and Union Bay...... E‐56 Figure E‐53. Sediment concentration relative to the SCO criterion for total DDDs in Lake Union/Ship Canal and Union Bay...... E‐57 Figure E‐54. Sediment concentration relative to the CSL criterion for total DDDs in Lake Union/Ship Canal and Union Bay...... E‐58

King County E‐3 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E‐55. Sediment concentration relative to the SCO criterion for total DDEs in Lake Union/Ship Canal and Union Bay...... E‐59 Figure E‐56. Sediment concentration relative to the CSL criterion for total DDEs in Lake Union/Ship Canal and Union Bay...... E‐60 Figure E‐57. Sediment concentration relative to the SCO criterion for total DDTs in Lake Union/Ship Canal and Union Bay...... E‐61 Figure E‐58. Sediment concentration relative to the CSL criterion for total DDTs in Lake Union/Ship Canal and Union Bay...... E‐62 Figure E‐59. Sediment concentration relative to the SCO criterion for total PAHs in Lake Union/Ship Canal and Union Bay...... E‐63 Figure E‐60. Sediment concentration relative to the CSL criterion for total PAHs in Lake Union/Ship Canal and Union Bay...... E‐64 Figure E‐61. Sediment concentration relative to the SCO criterion for tributyltin in Lake Union/Ship Canal and Union Bay...... E‐65 Figure E‐62. Sediment concentration relative to the CSL criterion for tributyltin in Lake Union/Ship Canal and Union Bay...... E‐66 Table E‐1. Bioassay results for each site. Results of quality control (QC) tests noted and failures highlighted...... E‐67

King County E‐4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-1. Sediment concentration relative to the SCO criterion for ammonia in Lake Union/Ship Canal and Union Bay.

King County E‐5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-2. Sediment concentration relative to the CSL criterion for ammonia in Lake Union/Ship Canal and Union Bay.

King County E‐6 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-3. Sediment concentration relative to the SCO criterion for total sulfides in Lake Union/Ship Canal and Union Bay.

King County E‐7 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-4. Sediment concentration relative to the CSL criterion for total sulfides in Lake Union/Ship Canal and Union Bay.

King County E‐8 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-5. Sediment concentration relative to the SCO criterion for arsenic in Lake Union/Ship Canal and Union Bay.

King County E‐9 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-6. Sediment concentration relative to the CSL criterion for arsenic in Lake Union/Ship Canal and Union Bay.

King County E‐10 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-7. Sediment concentration relative to the SCO criterion for cadmium in Lake Union/Ship Canal and Union Bay.

King County E‐11 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-8. Sediment concentration relative to the CSL criterion for cadmium in Lake Union/Ship Canal and Union Bay.

King County E‐12 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-9. Sediment concentration relative to the SCO criterion for chromium in Lake Union/Ship Canal and Union Bay.

King County E‐13 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-10. Sediment concentration relative to the CSL criterion for chromium in Lake Union/Ship Canal and Union Bay.

King County E‐14 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-11. Sediment concentration relative to the SCO criterion for copper in Lake Union/Ship Canal and Union Bay.

King County E‐15 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-12. Sediment concentration relative to the CSL criterion for copper in Lake Union/Ship Canal and Union Bay.

King County E‐16 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-13. Sediment concentration relative to the SCO criterion for lead in Lake Union/Ship Canal and Union Bay.

King County E‐17 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-14. Sediment concentration relative to the CSL criterion for lead in Lake Union/Ship Canal and Union Bay.

King County E‐18 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-15. Sediment concentration relative to the SCO criterion for mercury in Lake Union/Ship Canal and Union Bay.

King County E‐19 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-16. Sediment concentration relative to the CSL criterion for mercury in Lake Union/Ship Canal and Union Bay.

King County E‐20 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-17. Sediment concentration relative to the SCO criterion for nickel in Lake Union/Ship Canal and Union Bay.

King County E‐21 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-18. Sediment concentration relative to the CSL criterion for nickel in Lake Union/Ship Canal and Union Bay.

King County E‐22 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-19. Sediment concentration relative to the SCO criterion for selenium in Lake Union/Ship Canal and Union Bay.

King County E‐23 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-20. Sediment concentration relative to the CSL criterion for selenium in Lake Union/Ship Canal and Union Bay.

King County E‐24 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-21. Sediment concentration relative to the SCO criterion for silver in Lake Union/Ship Canal and Union Bay.

King County E‐25 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-22. Sediment concentration relative to the CSL criterion for silver in Lake Union/Ship Canal and Union Bay.

King County E‐26 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-23. Sediment concentration relative to the SCO criterion for zinc in Lake Union/Ship Canal and Union Bay.

King County E‐27 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-24. Sediment concentration relative to the CSL criterion for zinc in Lake Union/Ship Canal and Union Bay.

King County E‐28 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-25. Sediment concentration relative to the SCO criterion for bis(2-ethylhexyl) phthalate in Lake Union/Ship Canal and Union Bay.

King County E‐29 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-26. Sediment concentration relative to the CSL criterion for bis(2-ethylhexyl) phthalate in Lake Union/Ship Canal and Union Bay.

King County E‐30 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-27. Sediment concentration relative to the SCO criterion for beta-hexachlorocyclohexane in Lake Union/Ship Canal and Union Bay.

King County E‐31 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-28. Sediment concentration relative to the CSL criterion for beta-hexachlorocyclohexane in Lake Union/Ship Canal and Union Bay.

King County E‐32 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-29. Sediment concentration relative to the SCO criterion for carbazole in Lake Union/Ship Canal and Union Bay.

King County E‐33 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-30. Sediment concentration relative to the CSL criterion for carbazole in Lake Union/Ship Canal and Union Bay.

King County E‐34 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-31. Sediment concentration relative to the SCO criterion for dibenzofuran in Lake Union/Ship Canal and Union Bay.

King County E‐35 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-32. Sediment concentration relative to the CSL criterion for dibenzofuran in Lake Union/Ship Canal and Union Bay.

King County E‐36 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-33. Sediment concentration relative to the SCO criterion for dibutyltin in Lake Union/Ship Canal and Union Bay.

King County E‐37 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-34. Sediment concentration relative to the CSL criterion for dibutyltin in Lake Union/Ship Canal and Union Bay.

King County E‐38 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-35. Sediment concentration relative to the SCO criterion for dieldrin in Lake Union/Ship Canal and Union Bay.

King County E‐39 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-36. Sediment concentration relative to the CSL criterion for dieldrin in Lake Union/Ship Canal and Union Bay.

King County E‐40 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-37. Sediment concentration relative to the SCO criterion for di-n-butyl phthalate in Lake Union/Ship Canal and Union Bay.

King County E‐41 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-38. Sediment concentration relative to the CSL criterion for di-n-butyl phthalate in Lake Union/Ship Canal and Union Bay.

King County E‐42 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-39. Sediment concentration relative to the SCO criterion for di-n-octyl phthalate in Lake Union/Ship Canal and Union Bay.

King County E‐43 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-40. Sediment concentration relative to the CSL criterion for di-n-octyl phthalate in Lake Union/Ship Canal and Union Bay.

King County E‐44 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-41. Sediment concentration relative to the SCO criterion for endrin ketone in Lake Union/Ship Canal and Union Bay. Note: endrin ketone was not detected – values shown are MDL.

King County E‐45 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-42. Sediment concentration relative to the CSL criterion for endrin ketone in Lake Union/Ship Canal and Union Bay. Note: endrin ketone was not detected – values shown are MDL.

King County E‐46 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-43. Sediment concentration relative to the SCO criterion for monobutyltin in Lake Union/Ship Canal and Union Bay.

King County E‐47 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-44. Sediment concentration relative to the CSL criterion for monobutyltin in Lake Union/Ship Canal and Union Bay.

King County E‐48 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-45. Sediment concentration relative to the SCO criterion for pentacholorphenol in Lake Union/Ship Canal and Union Bay.

King County E‐49 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-46. Sediment concentration relative to the CSL criterion for pentacholorphenol in Lake Union/Ship Canal and Union Bay.

King County E‐50 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-47. Sediment concentration relative to the SCO criterion for phenol in Lake Union/Ship Canal and Union Bay.

King County E‐51 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-48. Sediment concentration relative to the CSL criterion for phenol in Lake Union/Ship Canal and Union Bay.

King County E‐52 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-49. Sediment concentration relative to the SCO criterion for tetrabutyltin in Lake Union/Ship Canal and Union Bay.

King County E‐53 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-50. Sediment concentration relative to the CSL criterion for tetrabutyltin in Lake Union/Ship Canal and Union Bay.

King County E‐54 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-51. Sediment concentration relative to the SCO criterion for total PCBs in Lake Union/Ship Canal and Union Bay.

King County E‐55 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-52. Sediment concentration relative to the CSL criterion for total PCBs in Lake Union/Ship Canal and Union Bay.

King County E‐56 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-53. Sediment concentration relative to the SCO criterion for total DDDs in Lake Union/Ship Canal and Union Bay.

King County E‐57 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-54. Sediment concentration relative to the CSL criterion for total DDDs in Lake Union/Ship Canal and Union Bay.

King County E‐58 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-55. Sediment concentration relative to the SCO criterion for total DDEs in Lake Union/Ship Canal and Union Bay.

King County E‐59 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-56. Sediment concentration relative to the CSL criterion for total DDEs in Lake Union/Ship Canal and Union Bay.

King County E‐60 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-57. Sediment concentration relative to the SCO criterion for total DDTs in Lake Union/Ship Canal and Union Bay.

King County E‐61 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-58. Sediment concentration relative to the CSL criterion for total DDTs in Lake Union/Ship Canal and Union Bay.

King County E‐62 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-59. Sediment concentration relative to the SCO criterion for total PAHs in Lake Union/Ship Canal and Union Bay.

King County E‐63 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-60. Sediment concentration relative to the CSL criterion for total PAHs in Lake Union/Ship Canal and Union Bay.

King County E‐64 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-61. Sediment concentration relative to the SCO criterion for tributyltin in Lake Union/Ship Canal and Union Bay.

King County E‐65 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure E-62. Sediment concentration relative to the CSL criterion for tributyltin in Lake Union/Ship Canal and Union Bay.

King County E‐66 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table E-1. Bioassay results for each site. Results of quality control (QC) tests noted and failures highlighted. QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca CSL GWPLKUN GWP 47.6435 -122.3364 9/17/1985 10 Day TRUE TRUE TRUE TRUE Failure Mortality H. azteca MARCO90 W-3 47.6624 -122.3856 4/3/1990 10 Day TRUE NA FALSE FALSE Clear Mortality H. azteca Reference UNIMAR2 1 47.6466 -122.3404 1/29/1991 10 Day TRUE FALSE TRUE TRUE Failure Mortality H. azteca Reference UNIMAR2 2 47.6470 -122.3400 1/29/1991 10 Day TRUE FALSE TRUE TRUE Failure Mortality H. azteca Reference UNIMAR2 3 47.6460 -122.3409 1/29/1991 10 Day TRUE FALSE TRUE TRUE Failure Mortality H. azteca Reference UNIMAR2 4 47.6459 -122.3404 1/29/1991 10 Day TRUE FALSE TRUE TRUE Failure Mortality H. azteca Reference UNIMAR2 6 47.6460 -122.3394 1/29/1991 10 Day TRUE FALSE TRUE TRUE Failure Mortality H. azteca Reference UNIMAR2 7 47.6462 -122.3390 1/29/1991 10 Day TRUE FALSE TRUE TRUE Failure Mortality H. azteca Reference UNIMAR2 8 47.6426 -122.3407 1/29/1991 10 Day TRUE FALSE TRUE TRUE Failure Mortality H. azteca LUDD- Reference LKUNDRDK 47.6328 -122.3298 5/19/1992 10 Day TRUE FALSE TRUE TRUE SS1 Failure Mortality H. azteca LUDD- Reference LKUNDRDK 47.6341 -122.3302 5/19/1992 10 Day TRUE FALSE TRUE TRUE SS2 Failure Mortality

King County E‐67 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca LUDD- Reference LKUNDRDK 47.6354 -122.3301 5/19/1992 10 Day TRUE FALSE FALSE FALSE SS3 Failure Mortality H. azteca SEACOM94 SED1 47.6283 -122.3378 3/4/1994 10 Day TRUE NA FALSE FALSE Clear Mortality H. azteca SEACOM94 SED2 47.6283 -122.3378 3/4/1994 10 Day TRUE NA FALSE FALSE Clear Mortality H. azteca CSL SEACOM94 SED3 47.6283 -122.3378 3/4/1994 10 Day TRUE NA TRUE TRUE Failure Mortality H. azteca CSL TRI-STAR TS-A 47.6662 -122.3925 5/1/1997 10 Day TRUE NA TRUE TRUE Failure Mortality H. azteca CSL TRI-STAR TS-B 47.6662 -122.3928 5/1/1997 10 Day TRUE NA TRUE TRUE Failure Mortality H. azteca CSL TRI-STAR TS-C 47.6650 -122.3926 5/1/1997 10 Day TRUE NA TRUE TRUE Failure Mortality C. tentans SALIII97 4C2 47.6561 -122.3821 5/19/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans SCO SALIII97 4C2 47.6561 -122.3821 5/19/1997 10 Day TRUE TRUE FALSE TRUE Failure Mortality H. azteca SALIII97 4C2 47.6561 -122.3821 5/19/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans CSL SALIII97 4F2 47.6566 -122.3763 5/19/1997 10 Day TRUE TRUE TRUE TRUE Failure Growth

King County E‐68 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans CSL SALIII97 4F2 47.6566 -122.3763 5/19/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality H. azteca SALIII97 4F2 47.6566 -122.3763 5/19/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans SALIII97 7B2 47.6559 -122.3677 5/19/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans SCO SALIII97 7B2 47.6559 -122.3677 5/19/1997 10 Day TRUE TRUE FALSE TRUE Failure Mortality H. azteca CSL SALIII97 7B2 47.6559 -122.3677 5/19/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality C. tentans SALIII97 7C2 47.6540 -122.3651 5/19/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans CSL SALIII97 7C2 47.6540 -122.3651 5/19/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality H. azteca SALIII97 7C2 47.6540 -122.3651 5/19/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans SALIII97 2B2 47.6635 -122.3830 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans CSL SALIII97 2B2 47.6635 -122.3830 5/20/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality H. azteca SALIII97 2B2 47.6635 -122.3830 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality

King County E‐69 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans SCO SALIII97 2C2 47.6616 -122.3813 5/20/1997 10 Day TRUE TRUE FALSE TRUE Failure Growth C. tentans SALIII97 2C2 47.6616 -122.3813 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SALIII97 2C2 47.6616 -122.3813 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans CSL SALIII97 3B3 47.6639 -122.3937 5/20/1997 10 Day TRUE TRUE TRUE TRUE Failure Growth C. tentans SCO SALIII97 3B3 47.6639 -122.3937 5/20/1997 10 Day TRUE TRUE FALSE TRUE Failure Mortality H. azteca SCO SALIII97 3B3 47.6639 -122.3937 5/20/1997 10 Day TRUE TRUE FALSE TRUE Failure Mortality C. tentans SALIII97 3C3 47.6622 -122.3861 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans SALIII97 3C3 47.6622 -122.3861 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SALIII97 3C3 47.6622 -122.3861 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans SALIII97 4B2 47.6608 -122.3774 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans SALIII97 4B2 47.6608 -122.3774 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality

King County E‐70 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca SALIII97 4B2 47.6608 -122.3774 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans SALIII97 4B3 47.6609 -122.3756 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans CSL SALIII97 4B3 47.6609 -122.3756 5/20/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality H. azteca CSL SALIII97 4B3 47.6609 -122.3756 5/20/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality C. tentans SALIII97 4F4 47.6588 -122.3761 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans SALIII97 4F4 47.6588 -122.3761 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca CSL SALIII97 4F4 47.6588 -122.3761 5/20/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality C. tentans SALIII97 5B2 47.6622 -122.3837 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans SALIII97 5B2 47.6622 -122.3837 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SALIII97 5B2 47.6622 -122.3837 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans SALIII97 6A2 47.6606 -122.3731 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth

King County E‐71 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans SALIII97 6A2 47.6606 -122.3731 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SALIII97 6A2 47.6606 -122.3731 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans CSL SALIII97 6B3 47.6583 -122.3695 5/20/1997 10 Day TRUE TRUE TRUE TRUE Failure Growth C. tentans SCO SALIII97 6B3 47.6583 -122.3695 5/20/1997 10 Day TRUE TRUE FALSE TRUE Failure Mortality H. azteca SALIII97 6B3 47.6583 -122.3695 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans SALIII97 6C2 47.6581 -122.3737 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans SALIII97 6C2 47.6581 -122.3737 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SALIII97 6C2 47.6581 -122.3737 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans SALIII97 7A2 47.6572 -122.3676 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans SALIII97 7A2 47.6572 -122.3676 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SALIII97 7A2 47.6572 -122.3676 5/20/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality

King County E‐72 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans CSL SALIII97 1B3 47.6665 -122.3888 5/21/1997 10 Day TRUE TRUE TRUE TRUE Failure Growth C. tentans CSL SALIII97 1B3 47.6665 -122.3888 5/21/1997 10 Day TRUE TRUE TRUE FALSE Failure Mortality H. azteca SALIII97 1B3 47.6665 -122.3888 5/21/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans SALIII97 5A2 47.6655 -122.3925 5/21/1997 10 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans SALIII97 5A2 47.6655 -122.3925 5/21/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SALIII97 5A2 47.6655 -122.3925 5/21/1997 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans CSL SALIII97 8A2 47.6662 -122.3953 5/21/1997 10 Day TRUE TRUE TRUE TRUE Failure Growth C. tentans CSL SALIII97 8A2 47.6662 -122.3953 5/21/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality H. azteca CSL SALIII97 8A2 47.6662 -122.3953 5/21/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality C. tentans CSL SALIII97 8C3 47.6663 -122.3914 5/21/1997 10 Day TRUE TRUE TRUE TRUE Failure Growth C. tentans CSL SALIII97 8C3 47.6663 -122.3914 5/21/1997 10 Day TRUE TRUE TRUE TRUE Failure Mortality

King County E‐73 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca SCO SALIII97 8C3 47.6663 -122.3914 5/21/1997 10 Day TRUE TRUE FALSE TRUE Failure Mortality C. tentans Control LUUCSO00 535 47.6531 -122.3244 4/10/2000 10 Day FALSE TRUE FALSE FALSE Failure Growth C. tentans LUUCSO00 535 47.6531 -122.3244 4/10/2000 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SCO LUUCSO00 535 47.6531 -122.3244 4/10/2000 10 Day TRUE TRUE FALSE TRUE Failure Mortality C. tentans Control LUUCSO00 B535 47.6527 -122.3255 4/10/2000 10 Day FALSE TRUE FALSE FALSE Failure Growth C. tentans LUUCSO00 B535 47.6527 -122.3255 4/10/2000 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SCO LUUCSO00 B535 47.6527 -122.3255 4/10/2000 10 Day TRUE TRUE FALSE TRUE Failure Mortality C. tentans Control LUUCSO00 527 47.6432 -122.3338 4/11/2000 10 Day FALSE TRUE FALSE FALSE Failure Growth C. tentans LUUCSO00 527 47.6432 -122.3338 4/11/2000 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SCO LUUCSO00 527 47.6432 -122.3338 4/11/2000 10 Day TRUE TRUE FALSE TRUE Failure Mortality C. tentans Control LUUCSO00 A535 47.6530 -122.3247 4/11/2000 10 Day FALSE TRUE FALSE FALSE Failure Growth

King County E‐74 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans LUUCSO00 A535 47.6530 -122.3247 4/11/2000 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca SCO LUUCSO00 A535 47.6530 -122.3247 4/11/2000 10 Day TRUE TRUE FALSE TRUE Failure Mortality C. tentans Control LUUCSO00 C535 47.6511 -122.3275 4/13/2000 10 Day FALSE TRUE FALSE FALSE Failure Growth C. tentans LUUCSO00 C535 47.6511 -122.3275 4/13/2000 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca CSL LUUCSO00 C535 47.6511 -122.3275 4/13/2000 10 Day TRUE TRUE TRUE TRUE Failure Mortality C. tentans 21645- FWLKUN01 47.6456 -122.3136 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 2 Growth C. tentans 21645- Con. and FWLKUN01 47.6456 -122.3136 7/30/2001 10 Day FALSE FALSE FALSE FALSE 2 Ref. Failure Mortality H. azteca 21645- FWLKUN01 47.6456 -122.3136 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 2 Mortality C. tentans 21645- FWLKUN01 47.6497 -122.3153 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 3 Growth C. tentans 21645- Con. and FWLKUN01 47.6497 -122.3153 7/30/2001 10 Day FALSE FALSE FALSE FALSE 3 Ref. Failure Mortality H. azteca 21645- FWLKUN01 47.6497 -122.3153 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 3 Mortality

King County E‐75 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans 21645- FWLKUN01 47.6445 -122.3298 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 5 Growth C. tentans 21645- Con. and FWLKUN01 47.6445 -122.3298 7/30/2001 10 Day FALSE FALSE FALSE FALSE 5 Ref. Failure Mortality H. azteca 21645- FWLKUN01 47.6445 -122.3298 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 5 Mortality C. tentans 21645- FWLKUN01 47.6397 -122.3311 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 6 Growth C. tentans 21645- Con. and FWLKUN01 47.6397 -122.3311 7/30/2001 10 Day FALSE FALSE FALSE FALSE 6 Ref. Failure Mortality H. azteca 21645- FWLKUN01 47.6397 -122.3311 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 6 Mortality C. tentans 21645- FWLKUN01 47.6319 -122.3299 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 7 Growth C. tentans 21645- Con. and FWLKUN01 47.6319 -122.3299 7/30/2001 10 Day FALSE FALSE FALSE FALSE 7 Ref. Failure Mortality H. azteca 21645- FWLKUN01 47.6319 -122.3299 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 7 Mortality C. tentans 21645- FWLKUN01 47.6398 -122.3360 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 8 Growth C. tentans 21645- Con. and FWLKUN01 47.6398 -122.3360 7/30/2001 10 Day FALSE FALSE FALSE FALSE 8 Ref. Failure Mortality

King County E‐76 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca 21645- FWLKUN01 47.6398 -122.3360 7/30/2001 10 Day TRUE TRUE FALSE FALSE Clear 8 Mortality C. tentans 21645- FWLKUN01 47.6533 -122.2860 7/31/2001 10 Day TRUE TRUE FALSE FALSE Clear 1 Growth C. tentans 21645- Con. and FWLKUN01 47.6533 -122.2860 7/31/2001 10 Day FALSE FALSE FALSE FALSE 1 Ref. Failure Mortality H. azteca 21645- FWLKUN01 47.6533 -122.2860 7/31/2001 10 Day TRUE TRUE FALSE FALSE Clear 1 Mortality C. tentans 21645- FWLKUN01 47.6490 -122.3281 7/31/2001 10 Day TRUE TRUE FALSE FALSE Clear 4 Growth C. tentans 21645- Con. and FWLKUN01 47.6490 -122.3281 7/31/2001 10 Day FALSE FALSE FALSE FALSE 4 Ref. Failure Mortality H. azteca 21645- FWLKUN01 47.6490 -122.3281 7/31/2001 10 Day TRUE TRUE FALSE FALSE Clear 4 Mortality C. tentans 21689- CSL FWLKUN01 47.6300 -122.3331 8/14/2001 10 Day TRUE TRUE TRUE TRUE 1 Failure Growth C. tentans 21689- Con. and FWLKUN01 47.6300 -122.3331 8/14/2001 10 Day FALSE FALSE FALSE FALSE 1 Ref. Failure Mortality H. azteca 21689- SCO FWLKUN01 47.6300 -122.3331 8/14/2001 10 Day TRUE TRUE FALSE TRUE 1 Failure Mortality C. tentans 21689- FWLKUN01 47.6645 -122.3888 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 10 Growth

King County E‐77 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans 21689- Con. and FWLKUN01 47.6645 -122.3888 8/14/2001 10 Day FALSE FALSE FALSE FALSE 10 Ref. Failure Mortality H. azteca 21689- FWLKUN01 47.6645 -122.3888 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 10 Mortality C. tentans 21689- FWLKUN01 47.6467 -122.2760 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 11 Growth C. tentans 21689- Con. and FWLKUN01 47.6467 -122.2760 8/14/2001 10 Day FALSE FALSE FALSE FALSE 11 Ref. Failure Mortality H. azteca 21689- FWLKUN01 47.6467 -122.2760 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 11 Mortality C. tentans 21689- CSL FWLKUN01 47.6322 -122.3384 8/14/2001 10 Day TRUE TRUE TRUE TRUE 2 Failure Growth C. tentans 21689- Con. and FWLKUN01 47.6322 -122.3384 8/14/2001 10 Day FALSE FALSE FALSE FALSE 2 Ref. Failure Mortality H. azteca 21689- CSL FWLKUN01 47.6322 -122.3384 8/14/2001 10 Day TRUE TRUE TRUE TRUE 2 Failure Mortality C. tentans 21689- FWLKUN01 47.6395 -122.3388 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 5 Growth C. tentans 21689- Con. and FWLKUN01 47.6395 -122.3388 8/14/2001 10 Day FALSE FALSE FALSE FALSE 5 Ref. Failure Mortality H. azteca 21689- FWLKUN01 47.6395 -122.3388 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 5 Mortality

King County E‐78 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans 21689- CSL FWLKUN01 47.6444 -122.3414 8/14/2001 10 Day TRUE TRUE TRUE TRUE 6 Failure Growth C. tentans 21689- Con. and FWLKUN01 47.6444 -122.3414 8/14/2001 10 Day FALSE FALSE FALSE FALSE 6 Ref. Failure Mortality H. azteca 21689- FWLKUN01 47.6444 -122.3414 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 6 Mortality C. tentans 21689- FWLKUN01 47.6470 -122.3480 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 7 Growth C. tentans 21689- Con. and FWLKUN01 47.6470 -122.3480 8/14/2001 10 Day FALSE FALSE FALSE FALSE 7 Ref. Failure Mortality H. azteca 21689- FWLKUN01 47.6470 -122.3480 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 7 Mortality C. tentans 21689- FWLKUN01 47.6557 -122.3669 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 8 Growth C. tentans 21689- Con. and FWLKUN01 47.6557 -122.3669 8/14/2001 10 Day FALSE FALSE FALSE FALSE 8 Ref. Failure Mortality H. azteca 21689- FWLKUN01 47.6557 -122.3669 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 8 Mortality C. tentans 21689- FWLKUN01 47.6583 -122.3795 8/14/2001 10 Day TRUE TRUE FALSE FALSE Clear 9 Growth C. tentans 21689- Con. and FWLKUN01 47.6583 -122.3795 8/14/2001 10 Day FALSE FALSE FALSE FALSE 9 Ref. Failure Mortality

King County E‐79 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans RTCTAM02 LU-10 47.6424 -122.3343 3/13/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca RTCTAM02 LU-10 47.6424 -122.3343 3/13/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RTCTAM02 LU-7 47.6434 -122.3336 3/13/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca RTCTAM02 LU-7 47.6434 -122.3336 3/13/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RTCTAM02 LU-8 47.6432 -122.3392 3/13/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca RTCTAM02 LU-8 47.6432 -122.3392 3/13/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RTCTAM02 LU-9 47.6426 -122.3373 3/13/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca RTCTAM02 LU-9 47.6426 -122.3373 3/13/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RTCTAM02 LU-1 47.6444 -122.3371 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca RTCTAM02 LU-1 47.6444 -122.3371 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RTCTAM02 LU-2 47.6438 -122.3358 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality

King County E‐80 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca RTCTAM02 LU-2 47.6438 -122.3358 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RTCTAM02 LU-3 47.6443 -122.3389 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca RTCTAM02 LU-3 47.6443 -122.3389 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RTCTAM02 LU-4 47.6439 -122.3378 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca RTCTAM02 LU-4 47.6439 -122.3378 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RTCTAM02 LU-5 47.6434 -122.3366 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca RTCTAM02 LU-5 47.6434 -122.3366 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RTCTAM02 LU-6 47.6433 -122.3349 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality H. azteca RTCTAM02 LU-6 47.6433 -122.3349 3/14/2002 10 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans LU-H- CSL RJAC005 47.6442 -122.3383 7/16/2002 20 Day TRUE TRUE TRUE TRUE 1 Failure Growth C. tentans LU-H- CSL RJAC005 47.6442 -122.3383 7/16/2002 20 Day TRUE TRUE TRUE TRUE 1 Failure Mortality

King County E‐81 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca LU-H- Con. and RJAC005 47.6442 -122.3383 7/16/2002 28 Day FALSE FALSE FALSE FALSE 1 Ref. Failure Growth H. azteca LU-H- RJAC005 47.6442 -122.3383 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear 1 Mortality C. tentans LU-H- CSL RJAC005 47.6436 -122.3370 7/16/2002 20 Day TRUE TRUE TRUE TRUE 2 Failure Growth C. tentans LU-H- CSL RJAC005 47.6436 -122.3370 7/16/2002 20 Day TRUE TRUE TRUE TRUE 2 Failure Mortality H. azteca LU-H- Con. and RJAC005 47.6436 -122.3370 7/16/2002 28 Day FALSE FALSE FALSE FALSE 2 Ref. Failure Growth H. azteca LU-H- CSL RJAC005 47.6436 -122.3370 7/16/2002 28 Day TRUE TRUE TRUE TRUE 2 Failure Mortality C. tentans LU-L- CSL RJAC005 47.6422 -122.3355 7/16/2002 20 Day TRUE TRUE TRUE TRUE 10 Failure Growth C. tentans LU-L- CSL RJAC005 47.6422 -122.3355 7/16/2002 20 Day TRUE TRUE TRUE TRUE 10 Failure Mortality H. azteca LU-L- Con. and RJAC005 47.6422 -122.3355 7/16/2002 28 Day FALSE FALSE FALSE FALSE 10 Ref. Failure Growth H. azteca LU-L- RJAC005 47.6422 -122.3355 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear 10 Mortality C. tentans LU-L- RJAC005 47.6431 -122.3321 7/16/2002 20 Day TRUE TRUE FALSE FALSE Clear 11 Growth

King County E‐82 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans LU-L- CSL RJAC005 47.6431 -122.3321 7/16/2002 20 Day TRUE TRUE TRUE TRUE 11 Failure Mortality H. azteca LU-L- Con. and RJAC005 47.6431 -122.3321 7/16/2002 28 Day FALSE FALSE FALSE FALSE 11 Ref. Failure Growth H. azteca LU-L- RJAC005 47.6431 -122.3321 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear 11 Mortality C. tentans CSL RJAC005 LU-L-8 47.6430 -122.3405 7/16/2002 20 Day TRUE TRUE TRUE TRUE Failure Growth C. tentans CSL RJAC005 LU-L-8 47.6430 -122.3405 7/16/2002 20 Day TRUE TRUE TRUE TRUE Failure Mortality H. azteca Con. and RJAC005 LU-L-8 47.6430 -122.3405 7/16/2002 28 Day FALSE FALSE FALSE FALSE Ref. Failure Growth H. azteca RJAC005 LU-L-8 47.6430 -122.3405 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear Mortality C. tentans RJAC005 LU-L-9 47.6424 -122.3386 7/16/2002 20 Day TRUE TRUE FALSE FALSE Clear Growth C. tentans CSL RJAC005 LU-L-9 47.6424 -122.3386 7/16/2002 20 Day TRUE TRUE TRUE TRUE Failure Mortality H. azteca Con. and RJAC005 LU-L-9 47.6424 -122.3386 7/16/2002 28 Day FALSE FALSE FALSE FALSE Ref. Failure Growth H. azteca RJAC005 LU-L-9 47.6424 -122.3386 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear Mortality

King County E‐83 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans LU-M- CSL RJAC005 47.6441 -122.3401 7/16/2002 20 Day TRUE TRUE TRUE TRUE 3 Failure Growth C. tentans LU-M- CSL RJAC005 47.6441 -122.3401 7/16/2002 20 Day TRUE TRUE TRUE TRUE 3 Failure Mortality H. azteca LU-M- Con. and RJAC005 47.6441 -122.3401 7/16/2002 28 Day FALSE FALSE FALSE FALSE 3 Ref. Failure Growth H. azteca LU-M- RJAC005 47.6441 -122.3401 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear 3 Mortality C. tentans LU-M- CSL RJAC005 47.6437 -122.3390 7/16/2002 20 Day TRUE TRUE TRUE TRUE 4 Failure Growth C. tentans LU-M- CSL RJAC005 47.6437 -122.3390 7/16/2002 20 Day TRUE TRUE TRUE TRUE 4 Failure Mortality H. azteca LU-M- Con. and RJAC005 47.6437 -122.3390 7/16/2002 28 Day FALSE FALSE FALSE FALSE 4 Ref. Failure Growth H. azteca LU-M- RJAC005 47.6437 -122.3390 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear 4 Mortality C. tentans LU-M- RJAC005 47.6432 -122.3376 7/16/2002 20 Day TRUE TRUE FALSE FALSE Clear 5 Growth C. tentans LU-M- CSL RJAC005 47.6432 -122.3376 7/16/2002 20 Day TRUE TRUE TRUE TRUE 5 Failure Mortality H. azteca LU-M- Con. and RJAC005 47.6432 -122.3376 7/16/2002 28 Day FALSE FALSE FALSE FALSE 5 Ref. Failure Growth

King County E‐84 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca LU-M- RJAC005 47.6432 -122.3376 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear 5 Mortality C. tentans LU-M- RJAC005 47.6431 -122.3361 7/16/2002 20 Day TRUE TRUE FALSE FALSE Clear 6 Growth C. tentans LU-M- CSL RJAC005 47.6431 -122.3361 7/16/2002 20 Day TRUE TRUE TRUE TRUE 6 Failure Mortality H. azteca LU-M- Con. and RJAC005 47.6431 -122.3361 7/16/2002 28 Day FALSE FALSE FALSE FALSE 6 Ref. Failure Growth H. azteca LU-M- RJAC005 47.6431 -122.3361 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear 6 Mortality C. tentans LU-M- RJAC005 47.6433 -122.3348 7/16/2002 20 Day TRUE TRUE FALSE FALSE Clear 7 Growth C. tentans LU-M- CSL RJAC005 47.6433 -122.3348 7/16/2002 20 Day TRUE TRUE TRUE TRUE 7 Failure Mortality H. azteca LU-M- Con. and RJAC005 47.6433 -122.3348 7/16/2002 28 Day FALSE FALSE FALSE FALSE 7 Ref. Failure Growth H. azteca LU-M- RJAC005 47.6433 -122.3348 7/16/2002 28 Day TRUE TRUE FALSE FALSE Clear 7 Mortality C. tentans NLU- RTCPH202 47.6474 -122.3318 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 01 Mortality C. tentans NLU- CSL RTCPH202 47.6474 -122.3318 10/14/2002 20 Day TRUE TRUE TRUE TRUE 01 Failure Mortality

King County E‐85 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca NLU- RTCPH202 47.6474 -122.3318 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 01 Mortality C. tentans NLU- RTCPH202 47.6439 -122.3331 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 06 Mortality C. tentans NLU- RTCPH202 47.6439 -122.3331 10/14/2002 20 Day TRUE TRUE FALSE FALSE Clear 06 Mortality H. azteca NLU- RTCPH202 47.6439 -122.3331 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 06 Mortality C. tentans NLU- RTCPH202 47.6437 -122.3342 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 07 Mortality C. tentans NLU- RTCPH202 47.6437 -122.3342 10/14/2002 20 Day TRUE TRUE FALSE FALSE Clear 07 Mortality H. azteca NLU- RTCPH202 47.6437 -122.3342 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 07 Mortality C. tentans NLU- RTCPH202 47.6448 -122.3423 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 13 Mortality C. tentans NLU- RTCPH202 47.6448 -122.3423 10/14/2002 20 Day TRUE TRUE FALSE FALSE Clear 13 Mortality H. azteca NLU- RTCPH202 47.6448 -122.3423 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 13 Mortality C. tentans NLU- RTCPH202 47.6444 -122.3407 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 14 Mortality

King County E‐86 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans NLU- RTCPH202 47.6444 -122.3407 10/14/2002 20 Day TRUE TRUE FALSE FALSE Clear 14 Mortality H. azteca NLU- RTCPH202 47.6444 -122.3407 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 14 Mortality C. tentans NLU- RTCPH202 47.6459 -122.3421 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 15 Mortality C. tentans NLU- RTCPH202 47.6459 -122.3421 10/14/2002 20 Day TRUE TRUE FALSE FALSE Clear 15 Mortality H. azteca NLU- RTCPH202 47.6459 -122.3421 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 15 Mortality C. tentans NLU- RTCPH202 47.6451 -122.3403 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 17 Mortality C. tentans NLU- CSL RTCPH202 47.6451 -122.3403 10/14/2002 20 Day TRUE TRUE TRUE TRUE 17 Failure Mortality H. azteca NLU- RTCPH202 47.6451 -122.3403 10/14/2002 10 Day TRUE TRUE FALSE FALSE Clear 17 Mortality C. tentans NLU- RTCPH202 47.6470 -122.3317 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 02 Mortality C. tentans NLU- RTCPH202 47.6470 -122.3317 10/15/2002 20 Day TRUE TRUE FALSE FALSE Clear 02 Mortality H. azteca NLU- RTCPH202 47.6470 -122.3317 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 02 Mortality

King County E‐87 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass C. tentans NLU- RTCPH202 47.6457 -122.3319 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 04 Mortality C. tentans NLU- RTCPH202 47.6457 -122.3319 10/15/2002 20 Day TRUE TRUE FALSE FALSE Clear 04 Mortality H. azteca NLU- RTCPH202 47.6457 -122.3319 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 04 Mortality C. tentans NLU- RTCPH202 47.6445 -122.3334 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 05 Mortality C. tentans NLU- RTCPH202 47.6445 -122.3334 10/15/2002 20 Day TRUE TRUE FALSE FALSE Clear 05 Mortality H. azteca NLU- RTCPH202 47.6445 -122.3334 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 05 Mortality C. tentans NLU- RTCPH202 47.6434 -122.3353 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 08 Mortality C. tentans NLU- RTCPH202 47.6434 -122.3353 10/15/2002 20 Day TRUE TRUE FALSE FALSE Clear 08 Mortality H. azteca NLU- RTCPH202 47.6434 -122.3353 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 08 Mortality C. tentans NLU- RTCPH202 47.6433 -122.3371 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 10 Mortality C. tentans NLU- RTCPH202 47.6433 -122.3371 10/15/2002 20 Day TRUE TRUE FALSE FALSE Clear 10 Mortality

King County E‐88 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

QC QC Lati- Long- Test CSL SCO Study ID Site Date Control Reference Outcome tude itude Name Failure Failure Pass Pass H. azteca NLU- RTCPH202 47.6433 -122.3371 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 10 Mortality C. tentans NLU- RTCPH202 47.6446 -122.3389 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 12 Mortality C. tentans NLU- RTCPH202 47.6446 -122.3389 10/15/2002 20 Day TRUE TRUE FALSE FALSE Clear 12 Mortality H. azteca NLU- RTCPH202 47.6446 -122.3389 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 12 Mortality C. tentans NLU- RTCPH202 47.6456 -122.3396 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 16 Mortality C. tentans NLU- RTCPH202 47.6456 -122.3396 10/15/2002 20 Day TRUE TRUE FALSE FALSE Clear 16 Mortality H. azteca NLU- RTCPH202 47.6456 -122.3396 10/15/2002 10 Day TRUE TRUE FALSE FALSE Clear 16 Mortality

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King County E‐90 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

APPENDIX F: TISSUE CHEMISTRY Fish and shellfish tissue data are very limited for Lake Union/Ship Canal; few studies have been completed and most are not recent. This appendix briefly describes a 1991 Washington State Department of Ecology study of shellfish tissue from Lake Union and then presents tissue data collected by King County in 1997 and 2000–2001 from Lake Union/Ship Canal and compares them to Washington state human‐health standards.

1991 Ecology Study An earlier published report on fish tissue in Lake Union examined histopathology rather than chemistry (Ecology, 1991). Fish were caught during two sampling periods: (2) in June 1990 using a fyke net at Gas Works Park and at Navy Cove and (2) in September 1990 using a fyke net and electroshocking at Gas Works Park, Navy Cove, and Portage Bay. The liver, kidney, and gills of 157 fish were examined for abnormalities; the blood was also examined. (Navy Cove is located in southern Lake Union west of the Wooden Boat Center.) General findings were as follows:  Nuclear pleomorphism and non‐uniform vacuolation in the liver tissue were prominent in sculpins; these traits are frequently associated with chronic exposure to contaminants; liver preneoplasms were observed in two perch caught at Gas Works and Navy Cove. No other substantial liver lesions were observed.  Few lesions were observed in the kidneys and gills in all collected fish, and those observed were associated with parasitism or other infection.  The study recommended further examination of sculpin and brown bullhead because of their benthic habitat, tendancy to be non‐migratory, and observed liver lesions.

1997 and 2000–2001 King County Data In August 1997, King County collected largemouth bass, catfish, sucker, and crayfish from site 0527 in Lake Union southeast of Gas Works Park (King County, unpublished data, 2002). Tissues were analyzed for semivolatile organic compounds, PCBs, pesticides, and metals. Resident fish and edible crayfish tissue had roughly an order‐of‐magnitude greater concentration than juvenile Chinook salmon for PCBs, mercury, and tributyltin. All concentrations in the resident fish and crayfish, however, were below the Lowest Observable Effect Level for freshwater fish for these contaminants. This study did not follow standard sampling and quality assurance protocols, and its results are questionable.

During the salmonid migrations of 2000 and 2001, King County collected Chinook, sockeye, and coho salmon along Lake Union/Ship Canal, including below the Locks (Table F‐1). Their tissue was analzyed for PCBs, mercury, butyltins, tripentyltin, tripropyltin, 2,4,5,6‐ tetrachloro‐m‐xylene, and decachlorobiphenyl. Additionally, crappie, sucker, northern pike minnow, yellow perch, and smallmouth bass were caught in Lake Union and analyzed in winter 2000. The crappie tissue was tested for organic compounds only. As with the 1997

King County F‐1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal study, this study did not follow standard sampling and quality assurance protocols and its results are questionable.

Table F-1. King County salmonid tissue collection date, reference number, location, and characteristics. Mean Sample Date No. Collection Location Species Length Wild? Reference Range Caught (mm) West of Locks beneath Chinook 6/20/2000 3 ? ? WL_CH railroad bridge (class 0) 5/6/2001 – Lake Union (near Gas Sockeye 39 111 Yes LU_SE 6/26/2001 Works) 5/29/2001 Lake Union Chinook 23 104 Likely LU_CH1 6/12/2001& Lake Union (Gas Works Chinook 21 129 No LU_CH2 6/26/2001 & Montlake Cut) 6/15/2001 Locks (flumes) Chinook 3 ? No LKS_CH 6/26/2001 Montlake Cut Chinook 11 114 No MC_CH1 6/26/2001 Montlake Cut Chinook 1 90 Yes MC_CH2 7/31/2001 West of Locks Coho 1 230 Yes WL_CO

Comparison to Human Health Standards Several contaminants found in surface water and sediment could potentially bioaccumulate in the tissues of a variety of aquatic organisms such as fish and shellfish. Bioaccumulation in biota may affect not only the organism directly accumulating the contaminants but also consumers of those organisms including humans and a variety of wildlife species.

The Washington State Department of Health uses EPA’s Guidance for Assessing Chemical Contaminant Data for Use in Fish Advisories to determine health‐based comparison values (CVs) (EPA, 2000). CVs for metals in fish tissue were based on a consumption rate equal to two 8‐ounce meals per week or 59.7 g/day for non‐carcinogenic end points and were calculated for metals and organics using EPA’s chronic oral reference doses (RfDs) (Tables F‐2 and F‐3). RfDs represent an estimate of daily human exposure to a contaminant below which non‐cancer adverse health effects are unlikely and would not trigger a potential consumption advisory. CVs were calculated for non‐cancer endpoints associated with consumption of shellfish using the following equation:

CV non‐cancer = RfD * BW CR * CF Where: RfD = oral reference dose (mg/kg‐day). BW = mean body weight of the general population or subpopulation of concern (70 kg). CR = daily consumption rate based on two meals per week, 8 ounces per meal (59.7 g/d). CF = conversion factor (0.001 kg/g).

King County F‐2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table F-2. Oral reference doses (RfDs) used in calculating the comparison values for metals. Oral RfD RfD Source Metal Notes (mg/kg-day) Source Date Aluminum 1.0 NCEA 06/21/2001 Cadmium 0.001 IRIS 09/10/2014 Cadmium RfD for food was used. Chromium 0.003 IRIS 09/10/2014 Copper 0.04 HEAST 07/1/1997 Iron 0.3 NCEA 6/21/2001 RfD selected is applicable to Manganese 0.14 IRIS 09/10/2014 exposures via ingestion of food. Mercury 0.0001 IRIS 09/10/2014 As methylmercury Nickel 0.02 IRIS 09/10/2014 Selenium 0.005 IRIS 09/01/1991 Silver 0.005 IRIS 09/10/2014 Zinc 0.3 IRIS 09/10/2014

Table F-3. Oral reference doses (RfDs) used in calculating the comparison values for organics. Oral RfD RfD Source Analyte Notes (µg/kg-day) Source Date Aroclor 1254 0.02 IRIS 11/01/1996 Oral RfD Bis(2-Ethylhexyl) 20 IRIS 05/01/1991 Oral Rfd Phthalate Phenol 300 IRIS 09/30/2002 Oral RfD Tributyltin 0.3 IRIS 09/01/1997 Oral RfD

Metals Metal concentrations were generally lowest in largemouth bass, although these concentrations surpassed suckers in terms of arsenic and zinc and surpassed crayfish, catfish, and salmonids in terms of mercury (Tables F‐4 and F‐5). The pelagic habitat of the largemouth bass and their feeding strategy involve minimal ingestion of sediment containing high metal concentrations. Crayfish, a benthic species, showed the greatest concentrations of aluminum, arsenic, copper, iron, lead, manganese, nickel, and zinc.

Because of their lipophilic properties, methyl and elemental mercury tend to bioaccumulate in fish and increase with trophic levels. However, in the 1997 data, suckers had greater concentrations of these metals than largemouth bass. This anomaly may be attributed to the sampling location and the motility of largemouth bass compared to suckers. Serdar et al. (2000) concluded that nearshore mercury concentrations are greater than limnetic sediments in Salmon Bay. If this conclusion is transferrable to the rest of Lake Union, then these elevated concentrations should be found in species with nearshore habitats, such as suckers. A 1981 sample found a mercury concentration of 5.5 mg/kg‐DW at site 0532, a shallow nearshore site near site 0527. These data also suggest that largemouth bass do not primarily prey on suckers but on other species such as crayfish and catfish.

King County F‐3 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Table F-4. Metal concentrations in tissue at site 0527 (1997) in Lake Union and fish sampled in winter 2000. All values in mg/kg-ww. CV = comparison value. Large- Small- Sucker Sucker N Pike- Yellow Metal CV Catfish mouth Crayfish mouth (1997) (2000) minnow Perch Bass Bass Aluminum 1170 NA <0.99 2.41 <0.4 <0.4 <0.4 <0.4 <0.4 Arsenic NA 0.110 0.179 0.089 0.099 0.129 0.195 0.033 Chromium 1.17 NA 0.054 0.09 0.10 0.387 0.489 0.325 0.337 Copper 46.9 NA 0.343 9.38 0.416 0.310 0.340 0.222 0.255 Iron 352 NA 1.6 22.5 3.71 4.58 2.88 2.4 1.4 Lead NA <.02 0.074 <.02 0.019 <0.008 <0.008 <0.008 Manganese 164 NA 0.070 1.48 0.192 0.257 0.0681 0.0516 0.0595 Mercurya 0.117b 0.0384 0.104 0.091 0.302 0.199 0.758 0.292 0.177 Nickel 23.5 NA <.02 0.042 <.02 NA NA NA NA Selenium 0.585 NA 0.18 0.15 0.19 0.2 0.17 0.2 0.2 Zinc 352 NA 4.41 12.2 3.64 5.8 4.26 4.43 6.2 a. Total mercury measured. b. As methylmercury.

Table F-5. Total mercury concentrations in salmonids (2000-2001) by reference number. All values in mg/kg-ww. CV = comparison value. Metal CV WL_CH LU_SE LU_CH1 LU_CH2 LK_CH MC_CH1 MC_CH2 WL_CO Mercury 0.117b NA 0.0258 0.012 0.014 0.0158 0.011 NA 0.014 a a. Total mercury measured. b. As methylmercury.

For all salmonid samples, mercury concentrations were well below the CV and the concentrations in resident fish and crayfish populations (Table F‐5). While suckers are not commonly consumed by humans, some ingestion may occur. If this ingestion is at or above the estimated daily consumption rate of 59.7 g/day, then the non‐cancer endpoint is exceeded and human health may be jeopardized. In crayfish, the arsenic concentration was greater than the carcinogenic CV.

In the 2000 sampling, the tertiary predators (northern pikeminnow and smallmouth bass) had the greatest levels of arsenic and mercury; the benthic omnivores (suckers) contained the greatest amount of iron, lead, and manganese. Concentrations of aluminum, chromium, copper, and selenium were not discernible.

More than 95 percent of total mercury in fish tissue is in the organic monomethyl form (Bloom, 1992). Despite limited Lake Union samples and data regarding fish size, it appears that mercury concentrations in crayfish, piscivores, and benthic fish are greater in Lake Union than Lake Washington, assuming similar size classes. McIntyre (2004) found the following mean monomethylmercury concentrations in fish Lake Washington:  0.0234 mg/kg‐ww and 0.0120 mg/kg‐ww in large and small signal crayfish, respectively.  0.2605 mg/kg‐ww in smallmouth bass (largemouth bass were not sampled).

King County F‐4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

 0.0553 mg/kg‐ww in prickly sculpin, a benthic omnivore (suckers were not sampled).  0.0455 mg/kg‐ww in juvenile sockeye salmon.  0.4127 mg/kg‐ww and 0.0566 mg/kg‐ww in large and small northern pikeminnow, respectively.  0.2041, 0.0862, 0.0297 mg/kg‐ww in large, medium, and small yellow perch had, respectively.

McIntyre (2004) concluded that the primary source of mercury to Lake Washington is atmospheric deposition. The presence of larger concentrations in Lake Union/Ship Canal suggests another input of mercury in addition to atmospheric deposition.

Organics Similar to metals, the greatest concentrations of organics among the analyzed species were found in suckers. Exceptions to this were for dibutyltin in largemouth bass and phenol in crayfish (Table F‐6). In the 2000 sampling, the northern pikeminnow had the greatest concentration of PCBs. The other organics were less discernible, although dibutyltin concentrations appear to be greatest in smallmouth bass. Concentrations for tributyltin and PCB in suckers in 1997 differed greatly from those in 2000, possibly because of different sampling periods and locations.

PCB concentrations in fish tissue appear to be greater in Lake Washington than Lake Union, except for juvenile sockeyes which had similar in both lakes. This discrepancy may due to differences in the size and age of fish analyzed. There were greater concentrations of DDT metabolites in the Lake Union sucker than the Lake Washington sculpin; PCB concentrations were roughly equivalent. McIntyre (2004) found the following mean concentrations of total DDT and PCB in Lake Washington fish tissue:  63 mg/kg‐ww DDT and 371 µg/kg‐ww PCB in smallmouth bass (largemouth bass were not sampled).  9 mg/kg‐ww and 158 µg/kg‐ww in prickly sculpin, which is a benthic omnivore like suckers (suckers were not sampled).  24 mg/kg‐ww and 37 µg/kg‐ww in juvenile sockeye salmon.  258 mg/kg‐ww and 1071 µg/kg‐ww in large northern pikeminnow.  45 mg/kg‐ww and 140 µg/kg‐ww in small northern pikeminnow.  59 mg/kg‐ww and 191 µg/kg‐ww in large yellow perch.  49 mg/kg‐ww and 66 µg/kg‐ww medium yellow perch.  14 mg/kg‐ww 47 µg/kg‐ww in small yellow perch.

No organochlorines were detected in Lake Washington crayfish.

King County F‐5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Ecology (2010) concluded that concentrations of PCBs in the sediment of Lake Washington, ranging from 3.3 µg/kg‐DW to 57 µg/kg‐DW, are 98 percent responsible for the PCB concentrations in fish tissue and that concentrations of PCBs in the sediment are therefore potentially hazardous to human health via fish consumption. Concentrations of PCBs in Lake Union/Ship Canal sediment are zero to two orders of magnitude greater than that of Lake Washington, especially in the Lake Union basin and near the shore.

Further analysis is required to determine the levels of PCBs and other contaminants in fish tissue and to confidently compare them to Lake Washington and regional fish tissue data.

Table F-6. Organics concentrations at site 0527 in Lake Union (1997 and 2000). All values in µg/kg-ww. Only detected parameters provided. CV = comparison value; ND = nondetect; NA = not measured. Bolded values indicate exceedance of human health- based comparison values. 1997 2000 Large- Small- Analyte CV Cat- Cray- N Pike- Crap- Yellow mouth Sucker Sucker mouth fish fish minnow pie Perch Bass Bass 4,4'-DDD <1.2 <1.3 <1.3 5.16 NA NA NA NA NA 4,4'-DDE <1.2 <1.3 <1.3 9.47 NA NA NA NA NA Aroclor 1254 23.5 <12 <13 <13 22 50 307 29 7.4 8.6 Aroclor 1260 <12 <13 <13 33 51.5 176 13.1 <5 <5 Total PCB ND ND ND 55 152 483 42 7.4 8.6 Aroclors Bis(2- Ethylhexyl) 23,500 NA <16 22 <16 NA NA NA NA NA Phthalate Dibutyltin NA 11.3 2.27 2.41 1.4 2.62 7.28 NA NA Mono-butyltin NA <2.2 <2.2 3.6 <3.4 <2.9 <3.3 NA NA Phenol 350,000 NA <110 7880 <110 NA NA NA NA NA Tributyltin 352 NA 92.6 3.2 96.9 13.2 19.3 19.3 NA NA Total Solids 19.9 22.4 16.8 22.3 23.3 23.9 22.1 NA 20.8

Table F-7. Organics concentrations in salmonids 2000-01 by reference number. All values in µg/kg-ww. Only detected parameters provided. CV = Comparison Value. Bolded values indicate exceedance of human health-based comparison values. Analyte CV WL_CH LU_SE LU_CH1 LU_CH2 LK_CH MC_CH1 MC_CH2 WL_CO Aroclor 1254 23.5 NA 57.2 16.3 47.7 29.8 30 58 12.7 Aroclor 1260 NA 12.2 <4 <4 <4 <4 <7.8 <4 Total PCB NA 69.4 16.3 47.7 29.8 30 58 12.7 Aroclors 2,4,5,6- Tetrachloro-m- NA 3.77 7.01 8.52 7.67 10.0 16.1 7.25 xylene Decachloro- NA 8.67 11.3 10.2 10.1 11.1 19.5 9.26 biphenyl Tripentyltin NA 20.4 14.9 16.2 18.6 19.9 NA 39.0 Tripropyltin NA 22.8 16.5 17.0 17.4 19.9 NA 34.5 Total Solids NA 20.7 18.4 22.3 22.3 19.6 NA 13.4

King County F‐6 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

References

Bloom, N.S. 1992. On the chemical form of mercury in edible fish and marine invertebrate tissue. Canadian Journal of Fisheries and Aquatic Sciences 49: 1010‐1017.

Ecology. 1991. Lake Union fish histopathology study. Prepared by ML Landolt and RA Busch. Washington State Department of Ecology. Environmental Investigations and Laboratory Services Program. Olympia, WA.

Ecology. 2010. General characterization of PCBs in south Lake Washington sediments. Prepared by B. Era‐Miller, R. Jack (King County), and J. Colton (King County). Washington State Department of Ecology. Environmental Assessment Program. Olympia, WA.

EPA. 2000. National guidance: Guidance for assessing chemical contaminant data for use in fish advisories: Volume 2, risk assessment and fish consumption limits. Washington, DC.

McIntyre, J.K. 2004. Bioaccumulation of mercury and organochlorines in the food web of Lake Washington. Jenifer K. McIntyre, Master's thesis, University of Washington, Seattle, WA.

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King County F‐8 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

APPENDIX G: PHYTOPLANKTON IN LAKE UNION/SHIP CANAL From 1993 through 2005, the monthly phytoplankton community in Lake Union/Ship Canal was examined qualitatively by genera at the Locks, Fremont, Dexter, I‐5 Bridge (NE Lake Union–Portage Bay), and Montlake sites. From 2003 forward, quantitative biovolume measurements and cell counts by genera were taken at the Dexter site. The qualitative data from 1997 through 2005 were used to compare the sites, and the quantitative data from 2009 through 2013 at Dexter were used to more closely investigate the phytoplankton community in the system.

Qualitative Data (1997–2005) From All Sites The qualitative data consist of identified plankton genera and their level of dominance (primary dominant, secondary dominant, or present). To quantify and visually display the 1997–2005 phytoplankton communities, numeric values (3, 2, and 1) were assigned to the qualitative signifiers.

The most common phytoplankton genera observed are Fragilaria, Melosira, Cryptomonas, Asterionella, Ulothrix, Tabellaria, Actinastrum, Diatoma, Dinobryon, Ankistrodesmus, Sphaerocystis, Anabaena, Oocystis, Microcystis, Aphanizomenon, Pediastrum, and Anacystis. The most common families are therefore bacillariophyta (diatoms), cryptophyta, chlorophyta (green algae), cyanobacteria (blue‐green algae), and chrysophyta. Dinoflaggellates and euglena were seldom found.

Species richness is usually greatest in July and August (Figure G‐1). September species richness values are likely strongly influenced by the presence of a cyanobacteria bloom, the dominance of the blooming Tabellaria species, the timing of destratification and turnover, and the flushing rate of the system. Monthly species richness values are similar between sites. The Fremont site, however, has slightly greater richness between July and October. While the quantitative data do not allow for comparison of phytoplankton densities, Tomlinson et al. (1977) noted that a site in southwest Lake Union had the greatest phytoplankton densities and that Ship Canal stations had the lowest; the authors attributed this difference to the high flushing action in the canal, which disperses potential blooms.

Phytoplankton communities were generally consistent between the five monitoring sites (Figure G‐2). The calculated abundance shown in Figure G‐2 is the relative share for each phylum of the sum of the monthly quantified dominance qualifiers. For example, three diatom, two chlorophyte, and one cyanobacteria species were identified in a sample. One of the diatom species was determined to be primary dominant, and the cyanobacteria species was secondary dominant. The diatom phylum is thereby assigned a value of 5 (3+1+1), the chrolophyte phylum is assigned a value of 2 (1+1), and the cyanobacteria phylum is assigned a value of 2. Thus, the relative abundances are 0.56, 0.22, and 0.22 for diatoms, chlorophytes, and cyanobacteria, respectively. This method skews toward diverse phyla

King County G‐1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

that are not necessarily dominant. This phenomenon is seen in late summer when species richness increases for phyla other than diatoms; the diatoms are typically dominant but not diverse.

The diversity and population of heterotrophic dinoflagellates and facultative heterotrophic chysophytes increase in the early summer as organic carbon becomes more plentiful in the water column following the spring productivity bloom. Similarly, cyanobacteria diversity and population increase in the summer, peaking in the latter part of the season as dissolved nitrogen (ammonia and nitrate/nitrite) becomes more limiting to phytoplankton. The ability of certain cyanobacteria (for example, Aphanizomenon, Anabaena) to fix molecular nitrogen gives them an advantage over other photoautotrophic species under nitrogen‐ limited conditions. Additionally, cyanobacteria can “luxury” uptake phosphorus, allowing them to hoard the often limiting orthophosphate (Wetzel, 2001).

King County G‐2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure G-1. Monthly phytoplankton species richness in Lake Union/Ship Canal (1997-2005).

King County G‐3 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Figure G-2. Relative phylum abundance in Lake Union/Ship Canal. King County G‐4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Qualitative Data (1997–2005) and Quantitative Data (2009–2013) from the Dexter Site The annual variation seen in the 1997–2005 qualitative data is echoed in 2009–2013 quantitative data from the Dexter site in Lake Union (Figure G‐3). Cryptophyte and chrysophyte biovolume typically peaked in April, cyanobacteria biovolume was greatest between June and November, and dinoflagellate biovolume was greatest in the late summer. A large increase in diatom biovolume, predominately Melosira and Stephanodiscus species, occurred in March, followed by high variability and a summertime dominance of Fragilaria. In August and September, a bloom of Tabellaria was evident.

The apparent dominance of diatoms shown in Figure G‐3 is largely skewed to the large size of diatoms relative to other phytoplankton phyla. For example, a single Tabellaria fenestrata cell is over 4,000 µm3/mL and a single Aphanothece spp. cell is under 5 µm3/mL. On a cell count basis, cyanobacteria compose between 10 and 90 percent of the phytoplankton in the summer, with diatoms comprising the majority of the remainder and cryptophyta and chlorophyta populations comprising a smaller, comparable portion. In the winter, diatoms, cryptophyta, or cyanobacteria have the greatest cell densities. Dominance may depend on ambient temperature, precipitation‐influenced turbidity, nutrient availability, and zooplankton grazing intensity.

In the early summer, between May and July, there is a period when biovolume and cell density are near wintertime values (Figure G‐4). This is likely due to the exhaustion of bioavailable nutrients in the euphotic zone and grazing by zooplankton such as Daphnia pulex. As cyanobacteria densities increase, this period ends. In many lakes, this period is termed the “clear water phase.” However, in Lake Union/Ship Canal, Secchi transparency depth is at its minimum in May. This departure may be due to the coincident peak flow of the Cedar River in May. A site in Lake Washington also has a transparency minimum in May.

Data Limitations  Sampling for cyanotoxins such as microcystin and anatoxin would provide insight on the threat to swimmers and other lake users presented by the late summer blooms of cyanobacteria.  Very little is known about the composition and magnitude of and the predation pressures on the zooplankton populations of Lake Union. Without this knowledge, it is difficult to say whether the algae blooms generally decline from lack of nutrients or from grazing pressure. Further, quantitative information is needed of predation on zooplankton and its effects on the floral‐faunal balance.

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Figure G-3. Monthly mean phytoplankton biovolumes at the Dexter site in Lake Union by phylum 2009-2013.

Figure G-4. Monthly mean diatom genera biovolumes at the Dexter site in Lake Union (2009-2013).

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Figure G-5. Monthly phytoplankton biovolume at the Dexter site in Lake Union (2009-2013).

References

Tomlinson, R.D., R.J. Morrice, E.C.S. Duffield, and R.I. Matsuda. 1977. A baseline study of the water quality, sediments, and biota of Lake Union. Municipality of Metropolitan Seattle. Seattle, WA.

Wetzel, R.G. 2001. Limnology: Lake and River Ecosystems. Academic Press. San Diego, CA.

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APPENDIX H: SALTWATER INTRUSION INTO LAKE UNION/SHIP CANAL The intrusion of salt water into Lake Union/Ship Canal is a unique characteristic of the system. Salt water introduced via the operation of the Hiram Chittenden Locks (Locks) passes through the shallow canal system and typically pools in the Lake Union basin but may sometimes reach as far as Portage Bay and Lake Washington (Seckel and Rattray, 1953; Tomlinson et al., 1977).

Evidence suggests that saltwater intrusion may release chemicals from Lake Union/Ship Canal sediments, but no direct studies have been completed to substantiate this phenomenon. Tomlinson et al. (1977) found elevated levels of phosphorus and dissolved zinc during saltwater intrusion, indicating that the highly contaminated sediments of Lake Union may threaten aquatic biota as the saltwater intrusion instigates the release of the sediment‐bound chemicals into the ambient water. In summer 2002, a large pulse of salt water entered Lake Union/Ship Canal and persisted until May of the following year (Figure H‐1). Sampling done during this period suggests that the prolonged saltwater layer led to buildup of metals, nutrients, and organic compounds in the hypolimnion in south Lake Union.

The following sections describe the extent and effects of this 2002 event, a 2013–2014 experiment of “false lockings” at the Locks, and the possible impacts of saltwater intrusion on the water available to dilute incoming sources of contamination.

Description of the 2002 Saltwater Intrusion Salinity values at the U.S. Army Corps of Engineers (USACE) site in northwest Lake Union (FBLW) suggest that the large pulse of salt water entered Lake Union in late May and June 2002 (Figure H‐2). The salt water began to enter the Lake Union basin on May 29 (USACE, unpublished data), after establishment of the thermocline in mid‐May. The salt layer at Dexter in south Lake Union persisted at 14 m until late March/early April 2003 and for a longer period near the sediments. Data from site FBLW indicate that additional pulses of salt water did not enter the system after the initial intrusion.

The salt water filled the southwestern basin of the lake but did not contribute as substantially to its northeastern basin (Figure H‐2(b)), possibly because of the baffling by the natural sill dividing the two basins and the greater turbulence in the northeastern basin caused by inflow from Lake Washington. Seckel and Rattray (1953) previously observed this pattern.

Routine monitoring data during the 2002 saltwater intrusion showed that increased temperature, sustained anoxia, and depressed pH occurred conterminously (Figures H‐3, H‐4, and H‐5). These conditions and the increased ionic strength associated with salt water may impact the speciation and bioavailability of sediment contaminants (Aggett and

King County H‐1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Kriegman, 1988; Bourg, 1988; Gambrell et al., 1991; Environment Canada, 2001; EPA, 2005; Bidwell and Gorrie, 2006; Zalizniak et al., 2006).

The cause of the pulse is unknown. It may have been a malfunction in the saltwater drain at the Locks that allowed salt water to accumulate in Salmon Bay east of the Locks and move upstream into the Lake Union basin (Kent Easthouse, personal communication, 2014).

Impacts on Metals, Nutrients, and Organic Compounds During the 2002 saltwater intrusion, a project to monitor dissolved metals, total metals, and organic compounds in Lake Union was nearing completion. Relevant sampling dates for dissolved and total metals were March 27, May 6, and July 3, 2002. The saltwater intrusion was evident at the Dexter site in southwest Lake Union only during the July date (Table H‐1). Organic compounds were sampled on March 19, June 10, and September 24, December 9, 2002, and March 3, 2003. Figures H‐6, H‐7, H‐8, and H‐9 graphically present the data for some of the analytes shown in Table H‐1.

Initially, the saltwater layer had a neutral pH (7.0), high dissolved oxygen (DO) (7.5 mg/L), and low suspended solids (1.7 mg/L) and turbidity (1.8 NTU) (Table H‐1; Figure H‐7). A little over a month after the intrusion, the salt layer had become anoxic (DO = 0.89 mg/L) and acidic (pH = 6.1) and suspended solids and turbidity had increased. After two months, suspended solids and turbidity had greatly increased relative to initial conditions. Turbidity continued to increase through the end of 2002; total suspended solids (TSS) concentrations peaked in October and then began to decline, potentially because of the settling of larger particles and decreases in algal debris loading from above. The saltwater layer remained anoxic and acidic throughout its duration.

Surprisingly, the January 2003 sample found a return to clearer conditions in terms of turbidity and TSS concentrations at depth but DO and salinity at the 14‐m depth were 0.35 mg/L and 4.5 ppt, respectively, suggesting continued stratified conditions. A mixing event may have occurred between the two sampling dates that distributed a portion of the saltwater layer throughout the water column. After the event, the dense saltwater may have reestablished at depth in Lake Union and the density gradient was reestablished.12

12 On December 25 and 27, 2002, northerly wind gusts reaching 20.1 and 23.2 m/s (45 and 52 mph), respectively, were observed at SeaTac International Airport (NCDC, 2014). The December 27, 2002, event was termed a Minor Windstorm (Read, 2004).

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a b

Figure H-1. Time-depth isopleths of salinity at Dexter in (a) 2001 and 2002 and in (b) 2002 and 2003during the saltwater intrusion.

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a FBLW

b GWLW

Figure H-2. Salinity at site FBLW in NW Lake Union (12.2-m depth near the Fremont Bridge) and site GWLW in NE Lake Union (11.0-m depth) in 2002 during the saltwater intrusion. Note that monitoring at GWLW ended in September 2002 and did not begin again until May 2013.

King County H‐4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal W Lake Union in (a) 2001 and 2002 and (b) 2002 and and (b) 2002 and and 2002 in (a) 2001 Union W Lake b b the saltwater intrusion. the saltwater intrusion. g 2003 during the saltwater intrusion. the saltwater 2003 during and 2003 durin and 2003 a a Figure H-3. at Dexter in S of temperature isopleths Time-depth Figure H-4. (b) 2002 and and 2002 2001 Union in (a) in SW Lake at Dexter oxygen dissolved of isopleths Time-depth

King County H‐5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal ion in (a) 2001 and 2002 and in (b) 2002 2002 2001 and ion in (a) b 2003 during the saltwater intrusion. the saltwater 2003 during a

Figure H-3. in SW Lake Un Dexter pH at of isopleths Time-depth

King County H‐6 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal between the two dates. An empty box signifies that An empty between the twodates. 2002 alue below the MDL. The dashed line between 5/6/2002 alue The dashed line between belowthe 5/6/2002 MDL. two dates. The slashed line btween two slashed line The 5/20/2002 and dates. organic compounds at the bottom of the Dexter site in NW Lake site in NW Lake bottom of the Dexter the at organic compounds al stratification between the intrusion. “<###” signifies a v signifies a “<###” intrusion. 11.9 11.8 10.4 3.65 7.5 0.89 0.4 0.35 0.37 0.17 0.0142 0.0082 <0.005 0.009 0.313 0.161.44 <0.40.55 1.21.25 0.58 2.86 2.2 2.9 2.6 15 0.685 0.65 4.8 oxygen, nutrients, metals, and oxygen, 1.3 3.1 3.54 1.7 2.3 16.6 3/19 3/27 4/1 4/15 5/6 5/20 6/3 6/10 6/19 7/1 7/3 7/15 8/5 8/20 0.84 1.0 1.2 1.8 3.9 29.0 Union during the 2002 saltwater the 2002 Union during and 5/20/2002 signifies that therm signifies that and 5/20/2002 6/3/2002 signifies that the saltwater wedge reached Lake Union Union Lake wedge reached saltwater the that 6/3/2002 signifies sampling date. on that measured wasnot the analyte

pHTotal Phosphorus (mg/L) 7.58 7.8 8.07 7.8 6.71 7 6.05 6.1 6.31 6.2 6.58 Analyte Sampling Depth (m)Salinity (ppt)Dissolved Oxygen (mg/L) 13 14 14 14.1 13.9 0.05 14.2 0.04 14 0.04 0.07 14 13.5 5.2 14 14 5.4 13.6 5.6 14.1 14 5.2 5.5 5.1 Total Nitrogen (mg/L)TSS (mg/L) (NTU) Turbidity 0.344 0.313 0.36 0.801 1.92 Total Aluminum (µg/L)Dissolved Arsenic (µg/L) 18.3 <100 3.1 Dissolved Chromium (µg/L) Dissolved Copper (µg/L) Total Iron (µg/L)Dissolved Lead (µg/L)(µg/L) Nickel Dissolved (µg/L) Zinc Dissolved 2-Methylnapthalene <0.025Acenapthene (µg/L) <0.094Acenapthylene <50 (µg/L) <0.0094Anthracene <0.0094(µg/L) Caffeine (µg/L) <0.20Carbazole (µg/L) <0.0094Dibenzofuran (µg/L)Fluoranthene (µg/L) 85 <0.0094 <0.024 0.036Fluorene (µg/L) <0.0094Naphthalene (µg/L)Phenanthrene (µg/L) <0.0094Pyrene <0.024(µg/L) <0.0094 <0.0094 <0.094 <0.0094 <0.0094 <0.0094 0.74 <0.0094 <0.024 0.0327 889 <0.0094 <0.0094 <0.0094 <0.024 <0.0094

Nutrients

Metals Organics Physical Parameters & & Parameters Physical Table H-1. dissolved Salinity,

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) eriod. p ling depth for conventionals in April, 2003. 0.47 0.8241.52 <0.0094 2.63 <0.024 0.6450.0120.0280.1060.264 0.7150.0360.242 0.022 0.0440.248 0.206 0.515 <0.094 0.0405 <0.0094 0.428 <0.0094 0.404 <0.024 <0.0094 <0.0094 <0.0094 <0.0094 2002 2003 0.0899 0.0815 0.0645 14 13.9 13.8 14 14 14 14 13.5 13.9 13.9 14.1 14.2 14 9/4 9/165.4 10/7 5.2 9/246.4 11/4 6.66 5 12/3 6.8 12/9 1/6 5 6.4 2/4 5.1 6.5 3/3 3/20 4/7 4.5 6.4 4/22 4.6 6.5 4.4 6.5 3.3 6.53 0.16* 7.6 0.05* 7.3 2.3717.838.8 2.59 30.4 45.7 3.06 22.3 4.56 53.3 5.6 60.6 0.035 0.285 1.6 0.272 1.1 1.4 1.1 3.7 1.6 0.32 4.5 1.3 0.58 0.71 0.34 0.59 0.73 0.83 0.52 0.76 6.21 8.5 8.11 0.253 1.1 1.02 2.61 0.0204 0.0143 0.0115 0.0161 Note metals were not were in this time not measured were not Note metals (

TSS (mg/L) (NTU) Turbidity 2-Methylnapthalene Carbazole (µg/L) Total Nitrogen (mg/L) Sampling Depth (m) Salinity (ppt) Dissolved Oxygen (mg/L) pH Total Phosphorus (mg/L) Acenapthene (µg/L) Acenapthylene (µg/L) (µg/L) Anthracene (µg/L)Caffeine Dibenzofuran (µg/L) Fluoranthene (µg/L) Fluorene (µg/L) Naphthalene (µg/L) Phenanthrene (µg/L) samp the Pyrene (µg/L)below present was ppt 4.7 approximately of salinity *A 0.0239 0.0297 <0.0094 Analyte

Nutrients

Organics Physical Parameters & & Parameters Physical

Table H-1. Continued.

King County H‐8 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal on lids concentrations, turbidity, and pH at Dexter in SW Lake Uni SW Lake in and pHDexter turbidity, at lids concentrations, during the 2002 salwater intrusion. salwater during the 2002

Figure H-6. so and total suspended salinity, oxygen, Dissolved

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phosphorus, arsenic, arsenic, phosphorus, ater intrusion. Note that , total phosphorus, dissolved arsenic, dissolved copper, and arsenic, dissolved dissolved , total phosphorus, Lake Union during the 2002 salw the 2002 Union during Lake ssolved oxygen, zinc salinity, ssolved dissolved chromium at Dexter SW dissolved copper, and chromium are displayed on a log-scale. on a log-scale. displayed chromium are copper, and Figure H-7. of di Concentrations

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nd phenanthrene at Dexter in SW nd phenanthrene orus, arsenic, copper, and chromium are displayed on and chromium are displayed copper, arsenic, orus, eine, carbazole, dibenzofuran, a r intrusion. Note that phosph intrusion. Note that r ssolved oxygen, salinity, caff oxygen, salinity, ssolved Lake Union during the 2002 salwate Union during the 2002 Lake a log-scale. a log-scale. Figure H-8. of di Concentrations

King County H‐11 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

orus, arsenic, copper, and chromium are displayed on and chromium are displayed copper, arsenic, orus, pthylene, anthracene, fluoranthene, and pyrene at Dexter in SW at Dexter and pyrene fluoranthene, anthracene, pthylene, r intrusion. Note that phosph intrusion. Note that r a log-scale. a log-scale. Lake Union during the 2002 salwate Union during the 2002 Lake Figure H-9. Figure H-9. acena salinity, oxygen, of dissolved Concentrations

King County H‐12 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Metals and Nutrients Limited analysis comparing July 3, 2002, metals concentrations to concentrations in samples collected earlier in 2002 shows increases in dissolved arsenic, barium, calcium, chromium, cobalt, copper, lead, magnesium, molybdenum, nickel, and zinc (Table H‐1; Figure H‐7). The July 2002 concentrations were higher than July concentrations in previous years (1999, 2000, and 2001) for arsenic, chromium, copper, lead, nickel, and zinc (Table H‐2). This difference may be due to the concentrations inherently present in the intruding salt water, to the sustained anoxia and low pH in the hypolimnion caused by the saltwater intrusion, and/or to terrestrial loading of these metals. Because the metals are predominantly in the dissolved fraction and epilimnetic values were substantially lower, terrestrial loading is not the likely prevailing source in 2002.13

To assist in determining the source of the metals, data from site KSQU01 were investigated. The site is located at Shilshole Bay and the mouth of the marine portion of Salmon Bay downstream from the Locks (249160 Northing, 1253227 Easting). Its maximum and median values are reported in Table H‐2. Given the observed concentrations and the large amount of dilution that must occur during Locks operations, saltwater intrusion does not appear to be the primary source of the elevated metals concentrations in Lake Union’s hypolimnion. Therefore, the principal driver of elevated metals concentrations is the onset of strong stratification resulting in hypolimnetic anoxia, the accompanying depression of pH, and seiching‐caused sediment resuspension. The resuspension of metals as the saltwater wedge travels through Salmon Bay may be an additional source of metals.

Table H-2. Comparison of analyte concentrations during different intensities of saltwater intrusion and the maximum 2000–2002 values detected at the Shilshole Bay site. 7/1 & Shilshole Shilshole Analyte 7/6/99 7/3/00 7/3/01 7/3/02 Maximum Median Salinity (ppt) 0.06 0.06 0.32 5.5 24.8 19.5 Dissolved oxygen (mg/L) 0.34 0.33 0.17 0.40 10.2 9.5 Potential range of days of 1 - 30 28 -48 15 - 34 12 - 30 NA NA anoxia before sample pH 7.0 7.0 6.5 6.1 >7.3 >7.3 Total phosphorus (mg/L) 0.0754 0.0428 0.0282 0.0090 0.0800 0.0548 Total nitrogen (mg/L) 0.707 0.520 0.551 0.801 NA NA Total aluminum (µg/L) <100 <100 <100 3.1 NA NA Dissolved arsenic (µg/L) 2.5 1.9 1.0 4.8 1.04 0.85 Dissolved chromium (µg/L) <0.4 <0.4 <0.4 2.2 0.13 0.042 Dissolved copper (µg/L) 1.5 1.7 2.09 2.9 2.46 1.31 Total iron (µg/L) 1080 555 694 889 NA MA Dissolved lead (µg/L) <0.2 <0.2 <0.2 0.74 0.016 0.012 Dissolved nickel (µg/L) 0.83 0.80 0.94 2.6 0.45 0.42 Dissolved zinc (µg/L) 3.47 4.86 8.32 15 5.01 3.25

13 Arsenic, chromium, copper, lead, nickel, and zinc were primarily observed in the dissolved fraction (60 to > 99 percent); dissolved aluminum was not detected (MDL = 2 µg/L).

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The impact of the prolonged anoxia and depressed pH on metals concentrations in 2002 cannot be determined because the monitoring program was discontinued. A buildup, however, of phosphorus, nitrogen, turbidity, and suspended solids is apparent during the stratification period (Table H‐1, Figures H‐10 and H‐11, and total phosphorus also shown in Figure H‐8). This buildup is expected to continue until mixing and the reintroduction of oxygenated waters occur.

As with TSS and turbidity, the January 2003 sampling found a return to lower total phosphorus and nitrogen concentrations at depth despite continued stratified conditions. These nutrients, too, may have been distributed and diluted during the December windstorms. After the mixing, total phosphorus and nitrogen concentration may not have rebounded because the sediments were well exhausted during the previous stratification, high flow conditions flushed the released nutrients from the system, and low biologic activity in the epilimnion prevented the uptake and resulting deposition of the nutrients.

Organics Figures H‐8 and H‐9 display the concentrations of detected organic compounds over the course of the 2002 saltwater intrusion. The figures also show DO and salinity. On March 19 prior to the saltwater intrusion and thermal stratification, caffeine was the only organic compound detected in Lake Union (Table H‐1). On the next sampling date on June 10 after thermal stratification and the saltwater intrusion had reached Lake Union, caffeine remained the only organic compound detected at a concentration similar to that detected in March. This indicates that the saltwater wedge did not introduce detectable levels of organic compounds.

The next sampling for organics occurred on September 24 after two to three months of hypolimnetic anoxia. On this date, many PAHs, caffeine, and carbazole were detected. On December 9, the same compounds were detected. For some compounds (acenapthene, anthracene, carbazole, dibenzofuran, fluorine, naphthalene, and phananthrene), the concentrations had increased substantially from September 24. On March 3, 2003, caffeine was the only organic compound detected. As discussed above, the compounds may have been redistributed in the water column or bound to large particles and fallen out of the water column during winter windstorms that caused brief hypolimnetic oxidation.

The concentrations of the organic compounds more closely follow the turbidity levels than TSS concentrations (Table H‐1). The organic compounds detected are hydrophobic (low water solubility) and are therefore unlikely to be found in the aqueous phase. Instead, they sorb preferentially to organic carbon‐rich particles in the sediments and water column. It is likely that the elevated organic compounds seen in Lake Union are bound to small particles (< 1.5 µm) not captured in TSS measurements. Filtering samples through a smaller pore size (such as 0.45 µm used for dissolved metals analysis) may provide some insight into the phase (whether aqueous or sorbed) of the organic compounds detected.

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The source of these particles bound to organic compounds cannot be definitely determined, but given the elevated concentrations of PAHs and carbazole in the sediments in southwest Lake Union, lake sediments are a likely source. Disturbance of the sediments by internal seiches may cause their resuspension (Gloor et al., 1994; Pierson and Weyhenmeyer, 1994). Input from the water above the saltwater layer is another potential source of contaminated particles. These inputs from above would pass more slowly through the saltwater layer than the fresh water above because of the density, allowing a buildup at the surface and within the saltwater layer.

U.S. Army Corps of Engineers False Lockings Experiments USACE is investigating potential methods to address salinity, temperature, and DO issues in Lake Union/Ship Canal. The investigation is pursuant to Section 7 of the Endangered Species Act concerning effects of operation and maintenance of the Lake Washington Ship Canal on threatened Puget Sound Chinook salmon, Puget Sound steelhead, and Coastal/Puget Sound bull trout and on designated critical habitat for Chinook and bull trout (USACE, 2012).

An expert panel submitted nine recommendations, including false lockings, to USACE in 2012. These recommendations seek to decrease summer water temperatures and increase summer DO concentrations for the benefit of migrating salmonids. The temperature of Lake Union/Ship Canal is continuously above optimum temperatures for salmonids during the summer months. The introduction of cooler seawater (approximately 15–17°C) may potentially decrease the temperatures of Salmon Bay. USACE is quantitatively examining the feasibility and benefits of these recommendations.

In 2013 and 2014, USACE performed in situ investigations of the effects of false lockings that resulted in substantial saltwater intrusions. For this experiment, USACE set daily quotas for the number of lock openings; these quotas were met whether boats were present or not. Additionally, the saltwater drain was turned off for set intervals (USACE, 2014). The 2013 saltwater intrusion persisted until February 2014, reaching a maximum salinity of 4 ppt at Dexter in southwest Lake Union in July 2013. The introduction of saltwater did marginally cool the near bottom water in Salmon Bay (USACE, 2014). The 2014 saltwater intrusion reached a maximum of 6.5 ppt at Dexter in August 2014 and remains within the deep holes of Lake Union as of May 2015.

King County H‐15 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal b b ons at Dexter in SW Lake Union in (a) 2001 and 2002 and 2002 and and Union in (a) 2001 Dexter in SW Lake ons at ations at Dexter in SW Lake Union in (a) 2001 and and Union in (a) 2001 Dexter in SW Lake at ations the saltwater intrusion. intrusion. saltwater the (b) 2002 and 2003 during the saltwater intrusion. the saltwater 2003 during and (b) 2002 2002 and (b) 2002 and 2003 during 2003 2002 and (b) 2002 and a a Figure H-10 Figure H-10 concentrati orthophosphate of isopleths Time-depth Figure H-11. Figure H-11. concentr of total phosphorus isopleths Time-depth

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Impacts on the Lake Volume Available for Dilution As surface runoff and discharges from stormwater and CSO outfalls enter the lake, they typically become well mixed throughout the system as the result of wind and flow action unabated by density gradients. With the presence of a saltwater layer, however, the volume of water available to dilute these inputs is reduced. Typically, the saltwater layer does not persist during the periods of high precipitation (fall through spring). An intense summertime saltwater intrusion, as seen in 2002, 2013, and 2014, can lead to stratified conditions persisting for an extended period, limiting the volume available for diluting inputs from stormwater and CSO outfalls.

The depth of the saltwater layer depends on the quantity of salt water that enters through the Locks. The layer does not typically come any nearer than 9 m to the surface because of the maintained depth of the canal channels. At the Dexter site in southwest Lake Union, the saltwater layer can typically be found below 10 m, which, based on the lake’s bathymetry, suggests that the entirety of the Lake Union basin sediments excluding those nearshore are inundated with salt water. This layer in Lake Union has a volume of 5.21*106 m3, which is 22 percent of the lake’s total volume. In the presence of stratified conditions, loaded contaminants in Lake Union’s surface could thus be approximately 128 percent of the concentration that would exist under unstratified conditions.

Recommend Studies Further analysis of the saltwater intrusion into Lake Union/Ship Canal is necessary to understand its impacts on the release of metals, organic compounds, and nutrients from the sediments. The analyses should answer the following questions:  What chemical species are released from the sediments during saltwater intrusion and at what quantity?  What is the fate of contaminants released during saltwater intrusion conditions? Do they remain or leave the system?  What are the impacts of increased salinity, prolonged anoxia, and depressed pH on the benthic and pelagic communities? Does sediment toxicity increase?

References

Aggett, J., and M.R. Kriegman. 1988. The extent of formation of arsenic (III) in sediment interstitial waters and its release to hypolimnetic waters in Lake Ohakuri. Water Research 22: 407‐411.

Bidwell, J.R., and J.R. Gorrie. 2006. The influence of salinity on metal uptake and effects in the midge Chironomus maddeni. Environmental Pollution 139: 206‐213.

Bourg, A.C.M. 1988. “Metal in aquatic and terrestrial systems: sorption, speciation, and mobilization” in Chemistry and Biology of Solid Waste. W Salomons, and U Förstner (eds.). Berlin, Springer‐Verlag, pp. 3‐32.

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Environment Canada. 2001. Priority substances list assessment report. Road salt. Canadian Environmental Protection Act, 1999. Environment Canada, Health Canada, Minister of Public Works and Government Services 2001, Ottawa, Ontario.

EPA. 2005. Technical resource document on monitored natural recovery. Prepared by Battelle. EPA/600/R‐14/083. Columbus, OH.

Gambrell, R.P., J.B. Wiesepape, W.H. Patrick, and M.C. Duff. 1991. The effects of pH, redox, and salinity on metal release from contaminated sediment: Water, Air, and Soil Pollution 57: 359‐367.

Gloor, M., A. Wuest, and M. Munnich. 1994. Benthic boundary mixing and resuspension induced by internal seiches. Hydrobiologia 284: 59‐68.

Pierson, D.C., and G.A. Weyhenmeyer. 1994. High resolution measurements of sediment resuspension above an accumulation bottom in a stratified lake. Hydrobiologia 284: 43‐57.

Read, W. December 27, 2002, minor wind storm. Office of the Washington State Climatologist. Accessed October 23, 2014. http://www.climate.washington.edu/stormking/December272002.html

Seckel, G.R. and M. Rattray Jr. 1953. Studies on Lake Washington ship canal. University of Washington Department of Oceanography. Technical Report 15.

Tomlinson, R.D., R.J. Morrice, E.C.S. Duffield, and R.I. Matsuda. 1977. A baseline study of the water quality, sediments, and biota of Lake Union. Municipality of Metropolitan Seattle, Seattle, WA.

USACE. 2012. Lake Washington Ship Canal Water Quality Science Panel Final recommendations report. US Army Corps of Engineers, Seattle District. Seattle, WA.

USACE. 2014. Lake Washington Ship Canal false locking study 2013: Temperature, salinity, and dissolved oxygen monitoring. U.S. Army Corps of Engineers, Seattle District, Hydraulics and Hydrology Branch, Water Management Section. Seattle, WA.

Zalizniak, L., B.J. Kefford, and D. Nugegoda. 2006. Is all salinity the same? I. The effect of ionic compositions on the salinity tolerance of five species of freshwater invertebrates. Marine and Freshwater Research 57: 75‐82.

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APPENDIX I: LITERATURE REVIEW

Study Area Characteristics and Uses CH2M Hill. 1975. Water circulation studies of Lake Washington. Prepared for the City of Seattle and the Municipality of Metropolitan Seattle.

City of Seattle. 2010. Shoreline Characterization Report. City of Seattle Department of Planning and Development. Seattle, WA.

Driggers, VV, Jr. 1964. Tracer dye studies in Lake Union and Bellingham Bay. Master ofScience thesis, University of Washington.

Ficken, RE. 1986. Seattle’s Ditch: The Corps of Engineers and the Lake Washington Ship Canal. Pacific Northwest Quarterly.

Jones and Stokes. 2001. Reference Biological Assessment Continued Operation and Maintenance of the Lake Washington Ship Canal. Prepared for U.S. Army Corps of Engineers, Seattle District, Seattle, Washington. Bellevue, Washington. August 2001.

King County. 2003. Sammamish/Washington Analysis and Modeling Program. Results of a Human Use Survey for Shoreline Areas of Lake Union, Lake Washington, and Lake Sammamish. Prepared by Parametrix, Inc. for King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, WA.

King County. 2009. Greater Lake Washington Watershed Human Helath Risk Assessment: Problem Formulation, Tier 1 and Tier 2. Prepared by Richard Jack and Jenée Colton, Water and Land Resources Division, Seattle, WA.

King County. 2011. Lake Washington/ Cedar/ Sammamish Watershed (WRIA 8) Land Cover Change Analysis. Prepared for WRIA8 Technical Committee by King County Water and Land Resources Division, Department of Natural Resources and Parks. Seattle, WA.

Montlake Landfill Work Group. 1999. Montlake Landfill Information Summary. Prepared by King County Departmetn of Public Health, University of Washington, Washington State Department of Ecology, and Washington State Department of Health. Seattle, WA.

Tobin, CC. 1986. Lake Union and Ship Canal Historical Use Study. Prepared for City of Seattle Lake Union/Ship Canal/Shilshole Bay Water Quality Management Program. Seattle, WA.

Toft, J, and C Simenstad, C Young, and L Stamatiou. 2003. Inventory and Mapping of City of Seattle Shorelines along Lake Washington, the Ship Canal and Shilshole Bay. 33pp.

King County I‐1 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Prepared for Seattle Public Utilities. Published by School of Aquatic and Fishery Sciences, University of Washington. Seattle, WA.

Troost, KG. 2011, Geomorphology and shoreline history of Lake Washington, Union Bay, and Portage Bay, Technical Memorandum, SR‐520 I‐5 to Medina Bridge Replacement and HOV Project, Prepared for Washington State Department of Transportation, Federal Highway Administration, September 2011, 92p.

Water Quality ACOE. 2004. Lake Washington Ship Canal Water Quality Monitoring and Analysis Plan. US Army Corps of Engineers, Seattle District, Hydrology and Hydraulics Section. Seattle, WA.

ACOE. 2014. Lake Washington Ship Canal False Locking Study 2013: Temperature, Salinity, and Dissolved Oxygen Monitoring . U.S. Army Corps of Engineers, Seattle District, Hydraulics and Hydrology Branch, Water Management Section. Seattle, WA.

Arhonditsis, GB, MT Brett, CL DeGasperi, and DE Schindler. 2004. Effects of climatic variability on the thermal properties of Lake Washington. Limnology and Oceanography 49: 256–270

Brandenberger, J. and A. James. 2013. Contaminants of emerging concern in the Salish Sea. The Encyclopedia of Puget Sound. Accessed 6/12/2014. http://www.eopugetsound.org/articles/contaminants‐emerging‐concern‐salish‐sea

City of Seattle, 1987. Lake Union/Ship Canal/Shilshole Bay Water Quality Management Program Data Summary Report Addendum, City of Seattle, Office for Long‐range Planning, Seattle, WA.

Collias, E, and G Seckel. 1954. Lake Washington Ship Canal Data, Special Report #2, Office of Naval Research, Contract N8onr‐520/III, Project NR 083012, Apr. 1954 .

Ecology. 2008. Trend Monitoring for Chlorinated Pesticides, PCBs, PAHs, and PBDEs in Washington Rivers and Lakes. Washington State Department of Ecology Environmental Assessment Program, Olympia, WA.

Herrera and Brown and Caldwell. 1994. Lake Union Water Quality/Environmental Assessment Project. Vol. 1, executive and technical summary; Vol. 2, project report; and Vol. 3, stormwater and basin maps. Herrera Environmental Consultants and Brown and Caldwell Consultants, Seattle, WA.

King County. 2003. Sammamish/Washington Analysis and Modeling Program. Lake Washington Existing Conditions Report. Prepared by Tetra Tech ISG, Inc and Parametrix, Inc. for King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, WA.

King County I‐2 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

King County. 2013. Estimating PCB and PBDE Loadings to the Lake Washington Watershed. Prepared for: U.S. Environmental Protection Agency Region 10; Submitted by: Richard Jack and Jenée Colton, King County Water and Land Resources Division, Seattle, WA.

Metro. 1993. Lake Union data compilation and review. Municipality of Metropolitan Seattle, Seattle, WA.

Rattray, M. Jr., GR SeckeI and CA Barnes. 1954. Salt budget in the Lake Washington Ship Canal system. Journal of Marine Research 13: 263‐275.

Rattray, M, Jr. and SR Shetye. 1982. Penetration and dilution of saline water between Lake Union and Lake Washington. University of Washington Department of Oceanography. Technical Report.

Seckel, GR and M Rattray Jr. 1953. Studies on Lake Washington ship canal. University of Washington Department of Oceanography. Technical Report 15.

Smith, V, and T Thompson. 1925. The Control of Sea Water Flowing into the Lake Washington Ship Canal. Industrial and Engineering Chemistry, Vol. 17, No. 10, 1084‐ 1087. October 1925.

Smith, V, and T Thompson. 1927. Salinity of the Lake Washington Ship Canal, Bulletin No. 41, University of Washington Engineering Experimental Station,Seattle, WA.

Smith, V and T Thompson. 1927. Occurrence of Hydrogen Sulfide in the Lake Washington Ship Canal. Industrial and Engineering Chemistry, Vol. 19, No. 7, 822‐823. July 1927.

Tomlinson, RD, RJ Morrice, ECS Duffield, and RI Matsuda. 1977. A baseline study of the water quality, sediments, and biota of Lake Union. Municipality of Metropolitan Seattle, Seattle, WA.

Sediment Quality Crecelius, EA. 1975. The geochemical cycle of arsenic in Lake Washington and its relation to other elements. Limnology and Oceanography 20: 441‐451

Ecology. 1986. Application of the Triad Approach to Freshwater Sediment Assessment: an Initial Investigation of Sediment Quality Near Gas Works Park, Lake Union. Prepared by Bill Yake, Dale Norton, and Margaret Stinson. Washington Department of Ecology, Olympia, WA.

King County I‐3 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Ecology. 2000. Concentrations of Chemical Contaminants and Bioassay Response to Sediments in Salmon Bay, Seattle Results of Phase III Sampling. Prepared by Dave Serdar, James Cubbage, and Dave Rogowski. Washington State Department of Ecology Environmental Assessment Program, Olympia, WA.

Ecology. 2003. Sediment Toxicity Near Gas Works Parks, Lake Union, Seattle. Prepared by R Jack. Washington State Department of Ecology. Environmental Assessment Program. Olympia, WA.

King County. 2001. Lake Union Sediment Study Sampling and Analysis Plan. King County, Department of Natural Resources and Parks. Modeling, Assessment, and Analysis Group. Seattle, WA.

King County. 2004. A Sediment Triad Analysis of Lakes Sammamish, Washington, and Union. King County Department of Natural Resources and Parks, Science Section, Seattle, WA.

Parametrix, Inc. 1992. Metro Toxic Sediment Remediation Project. Draft Final Report. Parametrix, Inc. Seattle, Washington.

Rogowski, D. 2000. Saltwater Intrusion in Salmon Bay and Lake Union Sediments. Washington State Department of Ecology. Olympia, WA.

Shannon & Wilson, Inc. 2008. Shallow Sediment Characterization Report. ACOE 2005‐ 00969 Permit Conditions. Prepared for Seattle Parks and Recreation Department. Seattle, WA.

Turney, GL and DF Goerlitz. 1990. Organic Contamination of Ground Water at Gas Works Park, Seattle, Washington. Groundwater Monitoring and Remediation 10: 187‐198.

Wakeham, SG, J Forrest, CA Masiello, Y Gélinas, CR Alexander, and PR Leavitt. 2004. Hydrocarbons in Lake Washington sediments. A 25‐year retrospective in an urban lake. Environmental Science & Technology 38: 431‐439.

Habitat and Wildlife ACEOE. 1999. Lake Washington Ship Canal, Section 1135 Smolt Passage Restoration Project, Biological Assessment. US Army Corps of Engineers Seattle District. CENWS‐ EC‐TB‐ER. Lake Washington Ship Canal Section 1135, Smolt Passage Restoration Project. May 16, 1999.

ACOE. 2012. Lake Washington Ship Canal Water Quality Science Panel Final Recommendations Report. US Army Corps of Engineers, Seattle District. Seattle, WA.

King County I‐4 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Barton, SB. 2000. Programmatic Biological Assessment for the Lake Washington Ship Canal – Supporting Hydraulic Analysis. U.S. Army Corps Of Engineers, Seattle District, Seattle, Washington. July 5, 2000.

Beauchamp, D. A., C. J. Sergeant, M. M. Mazur, J. M. Scheuerell, D. E. Schindler, M. D. Scheuerell, K. L. Fresh, D. E. Seiler, and T. P. Quinn. 2004. Spatial– temporal dynamics of early feeding demand and food supply for sockeye salmon fry in Lake Washington. Transactions of the American Fisheries Society 133:1014–1032.

Bennett and Cubbage, 1992. Effects of Polycyclic Aromatic Hydrocarbons (PAHs) in Sediments from Lake Washington on Freshwater Bioassay Organisms and Benthic Macroinvertebrates. Washington State Department of Ecology, Olympia, WA.

City of Seattle. 2000. Final Cedar River Watershed Habitat Conservation Plan. For the Issuance of a Permit to Allow Incidental Take of Threatened and Endangered Species. Seattle Public Utilities, Seattle, WA.

City of Seattle. 2003. “Lake Union/Lake Washington Ship Canal System” in Seattle’s Urban Blueprint for Habitat Protection and Restoration. Prepared by City of Seattle’s Salmon Team, Seattle, WA.

City of Seattle. 2012. Restoration and Enhancement Plan: City of Seattle Shoreline Master Plan. Prepared by Anchor QEA, LLC. Seattle, WA.

City of Seattle and ACOE. 2008. Synthesis of salmon research and monitoring, investigations conducted in the western Lake Washington Basin. Prepared by City of Seattle Public Utilities and US Army Corps of Engineers. Seattle, WA.

Ecology. 1991. Lake Union Fish Histopathology Study. Prepared by ML Landolt and RA Busch. Washington State Department of Ecology. Environmental Investigations and Laboratory Services Program. Olympia, WA.

Ecology. 2012. Biological Evaluation: Northlake Shipyard Sand Blast Grit Dredging – Interim Action. Washington State Department of Ecology, Seattle, WA

Fayram, AH. 1996. Impacts of largemouth bass (Micropterus salmoides) and smallmouth bass (Micropterus dolomieui) predation on populations of juvenile salmonids in Lake Washington. Masters thesis. University of Washington. Seattle, WA.

Fresh, K, E Warner, RA Tabor, and D Houck. 2000. Migratory behavior of adult Chinook Salmon spawning in the Lake Washington watershed in 1998 and 1999 as determined with ultrasonic telemetry. King County Wastewater Treatment Division, Seatle, WA.

King County I‐5 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

GLWTC. 2001. Greater Lake Washington Technical Committee. Reconnaissance Assessment‐Habitat Factors that Contribute to the Decline of Salmonids. Draft. Prepared for the Greater Lake Washington Steering Committee. Seattle, WA.

Kahler, T, M Grassley, and D Beauchamp. 2000. A summary of the effects of bulkheads, piers and other artificial structures and shorezone development on ESA‐listed salmonids in lakes. Washington Cooperative Fish & Wilde Research Unit, University of Washington, School of Fisheries, Seattle, WA.

Kerwin, J. 2001. Salmon and Steelhead Habitat Limiting Factors Report for the Cedar – Sammamish Basin (Water Resource Inventory Area 8) Washington Conservation Commission, Olympia, WA

King County. 2004. Major Lakes Phytoplankton Study: Comparison of Composite Sampling Techniques. Curtis DeGasperi, King County Water and Land Resources Division, Department of Natural Resources and Parks, Seattle, WA.

King County. 2010. Technical Memorandum, Habitat Project Opportunities: 2012 CSO Control Program Review. King County Wastewater Treatment Division, Seattle, WA.

LaLiberte D, and RD Ewing. 2006. Effect on Puget Sound Chinook Salmon Of NPDES Authorized Toxic Discharges As Permitted by Washington Department of Ecology.

Mantua, N, I Tohver and A Hamlet. 2010. Climate change impacts on streamflow extremes and summertime stream temperature and their possible consequences for freshwater salmon habitat in Washington State. Climatic Change, 102: 187‐223.

McIntyre, JK. 2004. Bioaccumulation of mercury and organochlorines in the food web of Lake Washington. Jenifer K. McIntyre, Master's thesis, University of Washington, Seattle, WA.

O’Neill, S.M. and J.E. West. 2001. Exposure of Pacific herring (Clupea pallasii) to persistent organic pollutants in Puget Sound and the Georgia Basin. In: Droscher, T. (ed). Proceedings of the 2001 Puget Sound Research Conference.

Peck, K.A., D.P. Lomax, O.P. Olson, S.Y. Sol, P. Swanson, and L.L. Johnson. 2010. Development of an enzyme‐linked immunosorbent assay for quantifying vitellogenin in Pacific salmon and assessment of field exposure to environmental estrogens. Environmental Toxicology and Chemistry 30(2):477‐486.

Pentec. 2010. Juvenile Salmon Use in Lake Union In Relation to Floating Home Complexes, Seattle, Washington. Prepared for Floating Homes Association; Prepared by Pentec Environmental,Seattle, WA.

King County I‐6 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Quinn, TP, CJ Sergeant, AH Beaudreau, and DA Beauchamp. 2012. Spatial and temporal patterns of vertical distribution for three planktivorous fishes in Lake Washington. Ecology of Freshwater Fish, 21: 337‐348.

R2 Resource Consultants . 2005. PIT Tagging of Juvenile Salmon Smolts in the Lake Washington Basin: Fourth Year (2003) Pilot Study Results and Synopsis of 2000– 2003 Findings. Prepared for US Army Corps of Engineers. Redmond, WA.

R2 Resource Consultants . 2007. PIT Tagging of Juvenile Salmon Smolts in the Lake Washington Basin: Fifth and Sixth Year (2004–2005) Pilot Study Results. Prepared for US Army Corps of Engineers. Redmond, WA.

Ross, P.S. 2006. Fireproof killer whales (Orcinus orca): Flame‐retardant chemicals and the conservation imperative in the charismatic icon of British Columbia, Canada. Canadian Journal of Fisheries and Aquatic Science 63:224‐234.

Ross, P.S., S.J. Jeffries, M.B. Yunker, R.F. Addison, M.G. Ikonomou, and J.C. Calambokidis. 2004. Harbor seals (Phoca vitulina) in British Columbia, Canada, and Washington State, USA, reveal a combination of local and global polychlorinated biphenyl, dioxin, and furan signals. Environmental Toxicology and Chemistry 23(1):157‐165.

Stinson, MD, and DL Eaton. 1983. Concentrations of lead, cadmium, mercury, and copper in the crayfish (Pacifasticus leniusculus) obtained from a lake receiving urban runoff. Archives of Environmental Contamination and Toxicology 12: 693–700.

Tabor, RA, MT Celedonia, F Mejia,RM Piaskowski, DL Low, B Footen, and L Park. 2004. Predation of juvenile Chinook salmon by predatory fishes in three areas of the Lake Washington basin. US Fish and Wildlife Service, Western Washington Fish and Wildlife Office, Lacey, WA.

Tabor, RA, HA Gearns, CM McCoy III, and S Camacho. 2006. Nearshore Habitat Use by Juvenile Chinook Salmon in Lentic Systems of the Lake Washington Basin, Annual Report, 2003 and 2004. US Fish and Wildlife Service,Western Washington Fish and Wildlife Office, Lacey, WA.

Tabor, RA, BA Footen, KL Fresh, MT Celedonia, F Mejia, DL Low, and L Park. 2007. Predation of juvenile Chinook salmon and other salmonids by smallmouth bass and largemouth bass in the Lake Washington basin. North American Journal of Fisheries Management 27:1174‐1188.

Toft, JD, AS Ogston, SM Heerhartz, JR Cordell, and EE Flemer. 2013. Ecological response and physical stability of habitat enhancements along an urban armored shoreline. Ecological Engineering 57: 97‐108.

USFW. 2008. Movement and Habitat Use of Junevile Chinook Salmon and Two Predatory Fishes in Lake Washington and the Lake Wahington Ship Canal: 2004‐2005 Acousitc

King County I‐7 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Tracking Studies. Prepared by MT Celedonia, ST Sanders, RA Tabor, DW Lantz, and I Grettenberger. US Fish and Wildlie Service. Lacey, WA.

USFW. 2011. Movement and Habitat Use of Chinook Salmon Smolts in the Lake Wahington Ship Canal: 2007‐2008 Acousitc Tracking Studies. Prepared by Cledonia, MT, Z Li, ST Sanders, RA Tabor, T Lee, S Damm, DW Lantz, and BE Price. US Fish and Wildlie Service. Lacey, WA.

Water Resource Inventory Area 8 Steering Committee (WRIA 8). 2005. Lake Washington/Cedar/Sammamish Watershed Chinook Salmon Conservation Plan. Seattle, WA.

Sources of Water Quality Concern and Corrective Actions ACOE. 2011. Final Environmental Assessment: Lake Washington Ship Canal Small Lock Monolith Repair, Seattle, King County, Washington. US Army Corps of Engineers Seattle District, Seattle, WA.

City of Seattle. 2000. Seattle public utilities CSO characterization project. City of Seattle, Seattle Public Utilities, Seattle, WA.

City of Seattle. 2009. Green stormwater operations and maintenance manual. City of Seattle, Seattle Public Utilities, Seattle, WA.

City of Seattle. 2010. 2010 CSO Reduction Plan Amendment. City of Seattle, Seattle Public Utilities. Seattle, WA.

City of Seattle. 2012. City of Seattle 2012 NPDES phase I municipal stormwater permit stormwater management program. City of Seattle, Seattle Public Utilities, Seattle, WA.

City of Seattle. 2013. Integrated plan: Briefing memorandum for April 29, 2013, expert panel meeting. City of Seattle, Seattle Public Utilities, Seattle, WA.

City of Seattle. 2014. 2014 NPDES phase I municipal stormwater permit stormwater management program. City of Seattle, Seattle, WA.

City of Seattle. 2014. Volume 3. Draft Integrated Plan. City of Seattle, Seattle, WA.

City of Seattle. 2014. Draft Executive Summary for The Plan to Protect Seattle’s Waterways. City of Seattle, Seattle Public Utilities. Seattle, WA.

Ecology. 2007. Oil spills in Washington State: A historical analysis. Revision of Publication No. 97‐252. Washington Department of Ecology, Spill Management Program, Olympia, WA.

King County I‐8 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Ecology. 2009. Oil Spill Risk in Industry Sectors Regulated by Washington State Department of Ecology Spills Program for Oil Spill Prevention and Preparedness. Prepared by Environmental Research Consulting. Washington State Department of Ecology. Olympia, WA.

Ecology. 2012. Stormwater management manual for Western Washington (five volumes). Publication No. 12‐10‐030. Washington State Department of Ecology, Water Quality Program, Olympia, WA.

GeoEngineers. 2013. Supplemental Investigation Work Plan, Gas Works Park Site, Seattle, Washington. Prepared for Puget Sound Energy. Seattle, WA.

King County. 2009. Comprehensive Sediment Quality Summary Report for CSO Discharge Locations. King County Wastewater Treatment Division. Seattle, WA.

King County. 2011. 2012 Comprehensive combined sewer overflow control program review, green stormwater infrastructure alternatives. Technical Memorandum 801. King County, Department of Natural Resources and Parks, Wastewater Treatment Division, Seattle, WA.

King County. 2011. CSO Sediment Quality Characterization: Final Sampling and Analysis Plan. King County Department of Natural Resources and Parks, Wastewater Treatment Division. Seattle, WA.

King County. 2012. 2012 King County Long‐term Combined Sewer Overflow Control Plan Amendment. King County Wastewater Treatment Division. Seattle, WA.

King County. 2012. Post Construction Monitoring Plan for King County CSO Controls. Prepared by Karen Huber, King County Wastewater Treatment Division, Seattle, WA.

King County. 2012. 2012 Stormwater Management Program. King County Department of Natural Resources and Parks, Water and Land Resources Division, Seattle, WA.

King County. 2012. Technical Memorandum 750: Sediment Deposition and Contamination Potential from Treated CSO Discharges. King County Wastewater Treatment Division. Seattle WA.

King County. 2013. Combined sewer overflow control program: 2012 annual report. King County Department of Natural Resources and Parks, Wastewater Treatment Division, Seattle, WA.

Metro. 1988. Final combined sewer overflow control plan ‐ plan for secondary treatment facilities and combined sewer overflow control: An amendment to Metro’s comprehensive water pollution abatement plan. Municipality of Metropolitan Seattle, Seattle, WA.

King County I‐9 October 2017 Water Quality Assessment and Monitoring Study: Analysis of Existing Data on Lake Union/Ship Canal

Metro 1992. Feasibility study CSO Control for Lake Union and Denny Regulator. Assessment of several engineering alternatives for CSO control and ranking of alternatives. Municipality of Metropolitan Seattle, Seattle, WA.

Metro 1993. University regulator CSO control project. Lake Union baseline environmental characterization. Municipality of Metropolitan Seattle, Seattle, WA.

WSDOT. 2011. SR 520, I‐5 to Medina: Bridge Replacement and HOV Project Environmental Impact Statement. Washinton State Department of Transportation, Seattle, WA.

WSDOT. 2011. JARPA Attachment I, Final Aquatic Mitigation Report: SR 520, I‐5 to Medina: Bridge Replacement and HOV Project. Washinton State Department of Transportation, Seattle, WA.

WSDOT. 2011. JARPA Attachment I, Final Wetland Mitigation Report: SR 520, I‐5 to Medina: Bridge Replacement and HOV Project. Washinton State Department of Transportation, Seattle, WA.

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