Lake Union/Ship Canal Key Findings

Home , Fremont Cut, Lake Union, Montlake Cut, Portage Bay

Tim Clark June 10, 2015 King County CSO Water Quality Assessment and Monitoring Study

Summary of Key Concerns

• Water Quality – Issues: Bacteria, temperature, dissolved oxygen • Sediment Quality – Issues: Metals, PAHs, PCBs, butyltins, phthalates • Impacts of the Saltwater Intrusion – Issues: Resuspension of contaminated sediments, buildup of nutrients CSO WQA Study Areas

• Elliott Bay

• Lake Union/Ship Canal

• Duwamish Waterway Water Quality Monitoring Stations

• Monthly /bi-monthly April-October • 3 sites in greater Lake Union/Ship Canal in last 5 yrs • 2 sites discontinued in 2008 • KC data goes back to Gas Works 1970s and 80s. • 5 US ACOE sites since ~2000 • Temperature, conductivity, salinity

CSO and Stormwater Outfalls

• 7 KC CSOs • 2 controlled • 1 near-controlled • 4 to be controlled by 2030 • 26 Seattle CSOs • 17 controlled • 9 uncontrolled • 47 known stormwater outfalls

Water Quality: Productivity

• Lake Union is mesotrophic – Moderately productive • Spring and fall diatom blooms – Spring: Melosira & Stephanodiscus spp. – Fall: Tabellaria spp. – Productivity is limited by • Phosphorus • Sometimes nitrogen in summer – Abundance is limited by • Nutrients • Water Residence Time • Zooplankton? Water Quality: Standards • No violation of Ecology water quality standards for ammonia, metals, or organics. • Violations of bacteria standards often. – 303(d) listed • Lake Union/Ship Canal designated as Core Summer Salmonid Habitat (June 15 to September 15) • Exceedance of pH standards occasional (Std: 6.5 to 8.5). – Peaks associated with spring phytoplankton blooms. – Lows associated with summer hypolimnion • Temperature and dissolved oxygen levels threaten migrating salmonids. – Lakes do not have numeric standards – Relative to natural conditions, humans may not cause a(n) • Increase in 7-DADMax by 0.3 °C • Decrease in DO by 0.2 mg/L Water Quality: Temperature

• High summer temperatures may negatively impact migrating salmonids – 17°C - thermal stress – 21.5°C - migratory barrier and direct mortality • Near bottom/thermocline temperatures may accommodate salmonids – Potential oxygen deficiency and contaminants in hypolimnion Water Quality: Temperature

21.5°C – Barrier/Mortality

17°C – thermal stress

ACOE Fremont Bridge – 7-Day average of daily maximum (7-DADMax) Red – 5.5 m depth Blue – 9.4 m Black – 12.2 m depth Period of salmonid presence highlighted (June 15 to September 15) Water Quality: Dissolved Oxygen

>6 mg/L – Optimal for salmonids <4.25 mg/L – Stress salmonids <2 mg/L – Lethal to salmonids

KC SW Lake Union (Dexter) – twice-monthly profiles Red – Surface (<5 m) Blue – Mid-depths (5-10 m) Black – Bottom (>10 m) Period of salmonid presence highlighted Water Quality: Bacteria

2004-2013 Concentrations (Fremont + NE Lake Union – 2004-2008) Bacteria Number of Months in Violation of Ecology Standard West East (Downstream) (Upstream) Year Locks – Fremont – Dexter- SW NE Lake Montlake Cut Salmon Bay NW Lake Lake Union Union – Union Portage Bay 2004 10 0 0 0 0 2005 11 0 0 0 0 2006 9 4 0 0 0 2007 12 12 10 0 0 2008 2 0 0 0 0 2009 0 n.d. 0 n.d. 0 2010 1 n.d. 5 n.d. 0 2011 10 n.d. 9 n.d. 0 2012 2 n.d. 0 n.d. 0 2013 0 n.d. 0 n.d. 0 n.d. – no data Water Quality: Bacteria

Locks Dexter Montlake

Ecology Geomean Standard Water Quality Trends

• Increasing: – Surface temperature (1985-2013) • 0.029°C per year at SW Lake Union • Leads to stronger, longer stratification • Cooling trend in summer hypolimnion temperatures – 0.138° C per year • Decreasing: – Phosphorus (1985-2013) – Nitrogen (1993-2013) – Bacteria (1976-2013) Sediment Quality Primary Contaminants (In Order of Sediment Cleanup Objective Exceedances) • Nickel (widespread) • Bis(2-ethylhexyl)phthalate (BEHP/DEHP) • PCBs • Silver • PAHs – Majority are high molecular weight, especially fluoranthene and pyrene • Butyltins (TBT, MBT, DBT) • Arsenic, Mercury, Lead, DDE Sediment Highlights • Sediment near Dexter Ave CSO outfall in SW Lake Union had greatest number of exceedances. (15 of 32 criteria contaminants >SCO) • PAHs found throughout – Concentrations greatest near Gas Works in N LU • PCBs found throughout – Elevated in Portage Bay, Lake Union, and Fremont Cut • Large spike of DDT near 3rd Ave W CSO – 1,516 µg/kg-DW. All other sites <45 µg/kg-DW. Impacts of Saltwater Intrusion

• Typically: – Saltwater is confined to Salmon Bay – Little to no impact on stratification in Lake Union • Large saltwater intrusion in 2002 and 2013 – 2002: Malfunction of saltwater drain – 2013: False Lockings (repeated in 2014) • Increased lock operations • Shutdown of saltwater drain Impacts of Saltwater Intrusion Salinity

Dexter - SW Lake Union Area affected by saltwater intrusion (below 11 m) ~1.5*106 m (350 acres) of sediment

Impacts of Saltwater Intrusion Dissolved Oxygen and pH

Dexter - SW Lake Union

Dexter - SW Lake Union Impacts of Saltwater Intrusion Summary • Buildup of nutrients in saltwater layer (SRP & ammonia > 1 ppm – order of magnitude > typical summer values) – Reduction of iron, manganese in sediments. – No nitrification of ammonia under anoxic conditions. • Resuspension of contaminants from the sediments – Sustained anoxia – Depressed pH – Seiching of the saltwater layer • PAHs, carbazole, and dibenzofuran were identified in 2002. – PAHs detected in 2015. Other organic compounds not tested. Lake Union/Ship Canal • Water Quality – High summer temperature and low dissolved oxygen may threaten migrating salmonids – Bacteria counts are occasionally above standards, but concentrations have dropped over past 40 years • Sediment Quality – High PAHs, PCBs, metals, and phthalates may impede benthic species. Potential for movement through trophic levels for bioaccumulative chemicals. • Saltwater intrusion – May allow sediment recontamination of the water column through the alteration of physical conditions. – May elongate hypoxia/anoxic conditions and remove a cold- water refuge for salmonids