Revised Final Remedial Design Report River Mile 13.5 Sediment Study Area River Mile 13.5 Lower Willamette River Portland, Oregon
September 2, 2015
Prepared for: Portland General Electric Company 121 SW Salmon Street Portland, Oregon 97204
Prepared by:
111 SW Columbia, Suite 1500 Portland, Oregon 97201-5814
Job No. 60411869 25698205.02020 CONTENTS
1.0 INTRODUCTION ...... 1-1 1.1 Report Organization ...... 1-1 2.0 BACKGROUND ...... 2-1 2.1 Site Description ...... 2-1 2.2 Site History at RM 13.5 ...... 2-1 2.2.1 Historical Site Use ...... 2-2 2.2.2 Historical and Potential On-Going Sources, Upland Source Control ...... 2-2 2.3 Remedial Action Objectives and Remedial Goals ...... 2-3 2.4 Description of Existing Conditions at RM 13.5 ...... 2-3 2.4.1 Nature and Extent of Impacted Sediment ...... 2-4 2.4.2 Geotechnical Characteristics of RM 13.5 ...... 2-5 2.4.3 Fluvial Setting and Bathymetry ...... 2-6 2.4.4 Ecological Characteristics of Study Area ...... 2-6 2.4.5 River Use ...... 2-7 2.4.6 Engineering Constraints ...... 2-8 2.5 Target Area...... 2-8 3.0 BASIS OF DESIGN ...... 3-1 3.1 Isolation Cap Thickness ...... 3-1 3.1.1 Isolation Layer ...... 3-1 3.1.2 Armor Layer Design ...... 3-2 3.1.3 Construction Tolerances ...... 3-6 3.2 Construction Considerations ...... 3-7 3.2.1 Debris ...... 3-7 3.2.2 Material Placement Considerations ...... 3-8 3.2.3 Engineering Controls and Water Quality Turbidity Monitoring ...... 3-9 3.2.4 Green Remediation Strategies ...... 3-10 3.3 Impacts to Community ...... 3-11 3.3.1 Reduction in the Risk to Human Health and Ecological Receptors...... 3-11 3.3.2 Adherence to Floodplain Management Requirements ...... 3-12 3.3.3 Impacts to the Community during Construction ...... 3-12 3.3.4 Waterway Use Impacts ...... 3-13 4.0 PRE-IMPLEMENTATION REQUIREMENTS ...... 4-1 4.1 Permitting Requirements ...... 4-1 4.2 Project Monitoring Plans ...... 4-1 4.2.1 Construction Health and Safety Plan ...... 4-1 4.2.2 Construction Quality Assurance Plan ...... 4-2 4.3 Pre-Implementation Data Requirements...... 4-2
CONTENTS
4.3.1 Bathymetric Survey ...... 4-3 4.3.2 Diver Survey ...... 4-3 5.0 IMPLEMENTATION OF REMEDIAL DESIGN ...... 5-1 5.1 Project Management and Implementation Oversight ...... 5-1 5.2 Mobilization...... 5-2 5.2.1 Isolation Cap Material Verification ...... 5-2 5.2.2 Equipment and Material Staging ...... 5-2 5.2.3 Utility Clearance ...... 5-3 5.2.4 Installation of Engineering Controls ...... 5-3 5.3 Debris Removal ...... 5-4 5.3.1 Debris and Object Recovery ...... 5-4 5.3.2 Waste Management ...... 5-4 5.4 Cap Installation ...... 5-5 5.4.1 Material Placement ...... 5-5 5.4.2 Water Quality Monitoring During Construction ...... 5-6 5.4.3 Sediment Cores and Confirmation Surveys ...... 5-6 5.5 Restoration ...... 5-7 5.5.1 Removal of Engineering Controls ...... 5-7 5.5.2 Post-Construction Cap Monitoring and Maintenance ...... 5-7 5.5.3 Construction Completion Report ...... 5-8 5.5.4 Long-Term Monitoring and Maintenance Plan ...... 5-8 6.0 PROJECT SCHEDULE ...... 6-1 7.0 REFERENCES ...... 7-1
CONTENTS
TABLES Table 1 Infrastructure and Taxlot Summary Table 2 Remedial Action Objectives and Goals Table 3 Cleanup Levels Table 4 Surface Sediment Results Table 5 Subsurface Sediment Results Table 6 Summary of Grain Size Data Table 7 SWAC Values Table 8 Permissible Shear and Velocity for Selected Capping Materials Table 9 Summary of Monitoring Requirements
FIGURES Figure 1 Site Plan Figure 2 Site Overview Figure 3 RM 13.5 Surface Sediment Areas above Screening Criteria & Mean Upriver Background Concentrations Figure 4 RM 13.5 Subsurface Sediment Areas above Screening Criteria & Mean Upriver Background Concentrations Figure 5 PGE RM 13.5 Remedial Action Schedule
APPENDICES Appendix A Calculations A-1a Fluvial Analysis A-1b No Rise Study for RM 13.5 A-2 Propeller Wash A-3a Ship Generated Wave Height A-3b Hudson’s Equation for Armor Stone Weight A-4 SiteWise™ Summary for Sustainability Appendix B Design Figures Appendix C Construction Quality Assurance Plan Appendix D Forms Appendix E Inspection Monitoring and Maintenance Plan
ACRONYMS AND ABBREVIATIONS
ADCP acoustic Doppler current profiler BMP best management practice bss below sediment surface CCR Construction Completion Report cfs cubic feet per second CHASP Construction Health and Safety Plan City City of Portland CL cleanup level cm centimeter COC constituent of concern Corps U.S. Army Corps of Engineers CQAP Construction Quality Assurance Plan cy cubic yard DDD dichlorodiphenyldichloro-ethane DDE dichlorodiphenyldichloro-ethylene DDT dichlorodiphenyltrichloro-ethane DDx sum of DDD, DDE, and DDT DEQ [Oregon] Department of Environmental Quality DFR daily field report DSL [Oregon] Department of State Lands dw dry weight ESA Endangered Species Act ESU Evolutionarily Significant Unit FEMA Federal Emergency Management Agency FS Feasibility Study ft foot FWS [U.S.] Fish and Wildlife Service IMMP Inspection Monitoring and Maintenance Plan IWCC in-water construction contractor kg kilogram LCR Lower Columbia River MSL mean sea level MUBC mean upriver background concentration n Manning’s roughness coefficient NAD North American Datum NAVD North American Vertical Datum ng nanogram NOAA National Oceanic and Atmospheric Administration OLW ordinary low water OMSI Oregon Museum of Science and Industry
ACRONYMS AND ABBREVIATIONS
PAH polycyclic aromatic hydrocarbon PCB polychlorinated biphenyl PCC Portland City Charter pcf pounds per cubic foot PGE Portland General Electric psf pounds per square foot QA/QC quality assurance and quality control RAO Remedial Action Objective RD Remedial Design RG Remedial Goal RI Remedial Investigation RM River Mile ROD Record of Decision SAP Sampling Analysis Plan SF square feet SWAC surface weighted area concentration TEQ total equivalency factor TOC total organic carbon TSS total suspended solids µg/kg micrograms per kilogram USGS U.S. Geological Survey
SECTIONONE Introduction
1.0 INTRODUCTION AECOM has prepared this Final Remedial Design (RD) Report, on behalf of Portland General Electric Company (PGE), to provide design, construction, and post-construction monitoring details for the remedial action selected for impacted river sediment in a discrete area at river mile (RM) 13.5 in the lower Willamette River (river). Remediation will be achieved by construction of an in-situ isolation cap over contaminated sediments and is designed to prevent exposure to human and ecological receptors and to reduce the mobility of contaminants in the underlying sediment. The RD Report was developed in accordance with the Oregon Department of Environmental Quality (DEQ) No. LQVC-NWR-12-07 Order on Consent issued July 16, 2012 (DEQ 2012). The rationale for the remedial action at RM 13.5 is described in the Record of Decision (ROD), prepared by the DEQ. This Final RD Report focuses only on the implementation of the remedial action described for the RM 13.5 Study Area. The remedial design for the RM 13.1 Study Area is expected to be completed in 2016 and will be presented separately. The RD components for the RM 13.5 Study Area presented in this RD Report address risk associated with elevated concentrations of total polychlorinated biphenyls (PCBs), dioxins/furans, pesticides, and polycyclic aromatic hydrocarbons (PAHs) (URS 2014). The Final RD Report describes the project history and background, engineering and geotechnical considerations, fluvial analysis, chemical evaluations, and permitting requirements for the isolation cap design at the RM 13.5 Study Area. The report is based on information available at the time of its preparation. Remedial design components specified in the Final RD Report may undergo changes as the permitting processes advance and/or if the pre-existing conditions (existing sediment surface elevation, sediment type, etc.) at the RM 13.5 Study Area are found to differ significantly from the current available information by the time the remedy is implemented. Copies of the approval and permit documents will be submitted under a separate cover letter before construction begins at RM 13.5. This RD report incorporates results from the following previously prepared reports for RM 13.5: Preliminary Assessment for RM 13.1 – 13.5 Drainage Areas (URS 2010a) Portland General Electric Willamette River Sediment Investigation (URS 2010b) Final Sediment Remedial Investigation Report River Miles 13.1 and 13.5, Willamette River, Portland, Oregon (URS 2011) Final Feasibility Study for River Miles 13.1 and 13.5, Willamette River, Portland, Oregon (URS 2014) Biological Assessment River Mile 13.5 Remedial Action, Multnomah County, Oregon (AECOM 2015a) Draft Remedial Design Report for River Mile 13.5 Study Area, River Mile 13.5, Willamette River, Portland, Oregon (AECOM 2015b)
1.1 Report Organization The remainder of the report is organized into the following sections: Section 2 describes the background, including the historical and current uses and characteristics for the RM 13.5 Study Area.
1-1 SECTIONONE Introduction
Section 3 describes the basis of design for the remedial action in RM 13.5 Study Area, which includes an isolation cap, and describes the isolation cap thickness, considerations for construction of the cap, and potential impacts of the remedial action to the community. Section 4 describes the project preparation tasks for implementing the remedial action at RM 13.5, including the permitting requirements, the project planning documents, and the pre- implementation data used to finalize the remedial design before project implementation. Section 5 identifies and describes the remedial activities to be implemented at the RM 13.5 Study Area, including mobilization, debris removal and isolation cap installation activities, and restoration activities including post-remedy monitoring. Ancillary tasks, including project management and reporting, are also described in Section 5. Section 6 provides the anticipated schedule for the project implementation. Section 7 lists the references for documents cited in the report text.
1-2 SECTIONTWO Background
2.0 BACKGROUND The remedy implementation for sediment at RM 13.5 will cap impacted sediment to prevent exposure to and mobility of the impacted sediment. PGE’s remedial activities in Downtown Reach (RM 13.1 and RM 13.5) are being phased over 2 years to effectively manage the remedial process, quality, and cost.
2.1 Site Description The RM 13.5 Study Area encompasses 94,852 square feet (SF) (2.18 acres) on the east side of the lower Willamette River, in the Downtown Reach Area of Portland, Oregon (Figure 1). The Study Area is located in Multnomah County. The majority of the Study Area is located below the ordinary low water (OLW) line and is owned by the Oregon Department of State Lands (DSL). The upland properties above the OLW include tax lots 200 and 203, owned by the Oregon Museum of Science and Industry (OMSI); and tax lot 202, owned by TriMet. The upland area is covered with asphalt, buildings, or landscaping. The Eastbank Esplanade, a pedestrian walking path, is located along the top of the riverbank through this area. The eastern bank adjacent to the Study Area is steeply graded and covered in riprap with no direct public access. The riprap shoreline grades steeply to the river bottom, which consists of fine granular sand with some gravel and woodchips in the sediment in the vicinity of the Study Area. Stormwater runoff from the upland properties is controlled and ground infiltrates or is discharged to either the City of Portland (City) or the TriMet stormwater system. Utilities and associated easements are present within the southern half of the Study Area, including two NW Natural gas lines, one active and one inactive; a City water line; an active City stormwater outfall, identified as ABU956; and an active TriMet outfall, identified as AQK79. The Tilikum Crossing Bridge is located overhead across the southern half of the Study Area. The constituents of concern (COCs) that are the risk drivers within the sediment in the Study Area include total PCBs, total dioxins/furans total equivalency factor (TEQ mammalian), and total DDx (sum of dichlorodiphenyldichloroethane [DDD], and its breakdown products dichlorodiphenyldichloroethylene [DDE] and dichlorodiphenyltrichloroethane [DDT]) (URS 2011). The COCs are present throughout the Study Area, and greater than 87 percent of the Study Area’s surface sediment is above the mean upriver background concentrations (MUBCs) in the surface sediment. The recommended remedy within the Study Area includes installation of an isolation cap over the Target Area (Figure 2) where the risk-driver COCs are co-located within the surface sediment. The Target Area consists of 48,547 SF (1.11 acres) within the northern portion of the Study Area where the isolation cap will be placed (Figure 2). The area is north of (outside of) the existing NW Natural gas line easement for the 20-inch active natural gas line.
2.2 Site History at RM 13.5 The Study Area is located on the eastern shore of the lower Willamette River in downtown Portland, Oregon, near RM 13.5 (Figure 1). The RM 13.5 Study Area was one of nine Focus Areas identified by the DEQ during the 2008 Downtown Portland Sediment Evaluation (DEQ 2009) study. A preliminary assessment conducted in 2010 identified the most likely sources of contamination to the site as the upland properties within the RM 13.5 drainage area, as well as potential releases during historical overwater activities. Impaired sediment and surface water from upstream sources were also identified as potential historical sources of contamination at the project area.
2-1 SECTIONTWO Background
In 2011, PGE prepared a Remedial Investigation Report (RI) (URS 2011) to determine if contaminants found in surface and subsurface sediments, including PCBs, dioxins/furans, pesticides, and some metals (copper, lead, mercury, zinc), exist at concentrations potentially posing an unacceptable risk to human health and ecological receptors. Based on the results of the RI, PGE prepared a Feasibility Study (FS) (URS 2014) report to describe the remedial action alternatives developed, screened, and evaluated to determine the appropriate cleanup action for RM 13.5. The Final FS recommended installation of an isolation cap as the proposed remedial action for the RM 13.5 Study Area.
2.2.1 Historical Site Use Historically, the Study Area bordered industrial upland properties with water-dependent and shoreline uses. The former Station L southern yard was an upland property owned by PGE, and electrical equipment was stored and operated from the mid-1930s to the 1970s. Historical spills to or within the project area may have occurred during the industrial use of these upland areas and associated in-water uses, which included boat building and log rafting (from approximately 1890 until the mid-1950s) and unloading fuel from a historical docking facility (from approximately 1957 to 1994).
2.2.2 Historical and Potential On-Going Sources, Upland Source Control Potentially complete and ongoing sources of contamination to RM 13.5 may include the following: Stormwater solids and RM 13.5 drainage area southern properties: Potentially contaminated stormwater and/or solids (e.g., soil, sediment, etc.) from roadways and railways may be transported into City Outfall ABU956, which directly discharges to the Study Area, as shown on Figure 2. An infiltration trench, approximately 100 feet (ft) long, was installed at the end of S.E. Caruthers Street during infrastructure improvements made to the ABU956 outfall system in 1997. Several recent improvements, including installation of bioswales within the drainage system, have been made to the stormwater management systems in the vicinity of RM 13.5 to accommodate the Portland to Milwaukie Light Rail project (Tilikum Crossing). However, the majority of the storm drainage discharging to ABU956 in the RM 13.5 Study Area does not have stormwater control measures in place. Also, the southern properties within the RM 13.5 drainage area may be releasing contaminants into the City Outfall ABU956 stormwater system, which subsequently discharges to the river. There are no current or, to PGE’s knowledge, prescribed discharge controls for City Outfall ABU956.
Potential spills/releases from over-water activities at Tilikum Crossing or the Portland Spirit dock may discharge directly to the river.
Contamination from sediment transport from upstream non-point sources may be transported downriver and impact the RM 13.5 Study Area. Two outfall pipes, City Outfall ABU956 and TriMet Outfall AQK795 (shown on Figure 2), currently discharge to the RM 13.5 Study Area (Table 1). The TriMet outfall pipe, Outfall AQK795, receives drainage from a series of bioswales adjacent to the Portland Opera House. Previous upland remedial activities at the former Station L have included the removal of soils from several areas where contaminant concentrations exceeded regulatory standards. In-water sediment remediation was also completed at the former Station L in 1991, in a study area located to the north of the
2-2 SECTIONTWO Background
RM 13.5 Study Area. The in-water remedy at Station L included dredging to remove the highest concentration of PCBs (maximum concentration of 21 parts per million), followed by the installation of a multi-layer isolation cap that was constructed of sand, gravel, and riprap that reached a maximum thickness of 6 ft in some areas. Monitoring and sediment cap maintenance for the Station L isolation cap is ongoing through 2020. At the RM 13.5 Study Area, the incomplete and/or insignificant pathways include groundwater migration, bank erosion, air deposition, and erosion/transport of “local” contaminated sediments immediately surrounding the Study Area (URS 2014). The remedial activities described in the Final RD Report are not intended to address the potential uncontrolled sources of recontamination to the surface sediment of the isolation cap placed in the Study Area from upstream or upgradient sources, as they fall outside the scope of work and are not PGE’s responsibility. Failure to address the potential uncontrolled sources of recontamination may compromise the effectiveness of the remedial work at reducing risks in the surface sediment. However, the isolation cap provides long-term protectiveness focused on reducing the risk of exposure from underlying contaminated sediment.
2.3 Remedial Action Objectives and Remedial Goals Table 2 presents the narrative remedial action objectives (RAOs) developed for the RM 13.5 Study Area, along with the narrative remedial goal (RG) for each RAO. The RGs focus on the results needed to achieve the RAO and consider applicable statutory and regulatory requirements, risk-based concentrations, upstream background concentrations for the risk drivers at RM 13.5, analytical detection limits standard guidance, and best practices for the industry. The risk drivers include total PCBs, dioxins/furans (TEQ protective of mammals), and total DDx. When applicable, the numeric expression of the RG is the site-specific cleanup level (CL); the CLs for the project are listed in Table 3. The CLs for the RM 13.5 Study Area were selected for the risk-driver COCs, including total PCBs, dioxins/furans TEQ, and total DDx. They include point-based action levels developed for discrete sediment sampling locations and study area-wide surface weighted average concentrations (SWACs), considering the human health and ecological receptors (URS 2011). Risk-based CLs developed for RAO 1 are based on the area-wide sampling (SWACs), as directed by DEQ (URS 2014) and are presented in Table 3. Best management practices (BMPs) will be used to achieve the other RAOs. The RAOs, described in Table 2, will be met immediately after the remedy is implemented at RM 13.5 (Time 0). Long-term monitoring will be conducted to confirm remedy protectiveness and compliance with RAOs over time.
2.4 Description of Existing Conditions at RM 13.5 The following subsections describe the existing conditions at the RM 13.5 Study Area, including the nature and extent of contamination, the geotechnical characteristics of the Study Area, the river use and ecological characteristics within the Study Area, the fluvial conditions, and the engineering constraints present in the RM 13.5 Study Area.
2-3 SECTIONTWO Background
2.4.1 Nature and Extent of Impacted Sediment For a more in-depth description of the nature and extent of impacted sediments, please refer to the RI (URS, 2011) and FS (URS 2014). The results of sediment sampling indicate the constituent concentrations are generally co-located with one another in the Study Area. The COCs present in the RM 13.5 Study Area will strongly adsorb to sediment due to their high sediment organic carbon-water partitioning coefficients values (URS 2014). The risk-driver COCs in the surface sediment include PCBs, dioxins/furans, and pesticides. A subset of these are the risk-driver chemicals, total PCBs, dioxins/furans (TEQ protective of mammals), and total DDx, which account for most of the exceedances and risk in the RM 13.5 Study Area. The RD footprint is based on the risk-driver chemicals. These risk drivers will tend to bind to sediment where elevated total organic carbon (TOC) concentrations are present and become less bioavailable. The average TOC value in the surface sediment at the RM 13.5 Study Area is 2.8 percent (range 0.58 to 9 percent) (URS 2014). Tables 4 and 5 summarize the surface and subsurface sample concentrations for the risk-driver COCs in the RM 13.5 Study Area. Surface sediment is defined as the sediment that extends 1 ft below the water/sediment interface (below sediment surface [bss]). The highest concentrations of total PCBs as Aroclors in surface sediment occurred at DPSC-G041 (134 micrograms per kilogram [µg/kg] dry weight [dw]) at 7.8 times the CL), with concentrations generally decreasing further downriver. The highest concentration of total PCBs as Aroclors in subsurface sediment was detected at DPSC-C022 (610 µg/kg dw). The highest concentrations of total dioxins/furans in the surface and subsurface sediment were detected at sampling location IPC-S022 (20.0 nanograms per kilogram [ng/kg] and 19.3 ng/kg, respectively, 10 times higher than the CL). The highest concentration of total DDx in surface sediment was detected at IPC-C019 (14.9 µg/kg dw, 5 times higher than the CL), located in the southern portion of the Study Area, in close proximity to the existing NW Natural 20-inch gas pipeline. The concentrations of total DDx increased with depth in the middle of the northern portion of the Study Area, with the highest concentration of total DDx detected in subsurface sediment sample DPSC-C022 (70.6 µg/kg dw), collected between approximately 3 and 5 ft bss. The estimated vertical extent of contamination has not been confirmed because of difficult coring in material and woody debris encountered at depth; the deepest sample collected during the RI/FS was about 6 ft. The areal extent of contaminated surface sediment above the CLs (based on interpolation by Thiessen polygons) is approximately 82,375 SF (1.89 acres [size of study area is approximately 2.18 acres]). The surface sample locations with one or more risk-driver COC concentrations above the MUBCs for the RM 13.5 Study Area are shown on Figure 3. The Thiessen polygon areas for the surface samples with risk- driver COCs above the MUBCs for RM 13.5 comprise 87 percent of the Study Area’s surface area. The subsurface sediment sample locations with risk-driver COCs above the MUBC in RM 13.5 are shown on Figure 4. The Thiessen polygon areas for subsurface samples above the MUBCs comprise the entire 94,852 SF (2.18 acres) Study Area. Site-specific SWACs were generated for the RM 13.5 Study Area risk-driver COCs using the data for all the surface sediment samples collected from a depth of less than or equal to 1 ft (30 centimeters [cm]) bss (URS 2014). The baseline SWAC values for the Study Area are presented in Table 6 for the risk driver COCs, including total PCBs, dioxins/furans (TEQ), and total DDx.
2-4 SECTIONTWO Background
2.4.2 Geotechnical Characteristics of RM 13.5 The geotechnical characteristics of the river bottom sediment and the adjacent riverbank are described in the following sections for RM 13.5. Geotechnical Characteristics of the River Bottom Sediments The river bottom elevation grades from the adjacent shoreline, at an elevation of approximately 9 ft North American Vertical Datum (NAVD) 88 (ordinary mean water elevation) to the lowest elevation of approximately -30 ft NAVD 88 at the northwestern boundary of the Study Area (Figure 2). The grain size distribution of four surface and three subsurface samples collected during the FS indicates the bedded sediment is predominantly silt with sand in the RM 13.5 Study Area (Table 6). Surface sediment is described by American Society of Testing Materials standard classification as a slightly clayey silt with sand and trace gravel with an average of 59 percent fines (sum of silt and clay fractions). Subsurface sediment is generally the same but slightly finer grained with an average of 66 percent fines. The sand fraction ranges from about 20 to 40 percent among the samples. Nonetheless, the low plasticity and low cohesion of the sediment indicates that the sediment may behave as non-plastic to low-plastic (non-cohesive) fine granular sand. The average total organic content measured in the sediment at RM 13.5 is 2.8 percent and 2.9 percent in the surface and subsurface sediment samples, respectively. The average moisture content of sediment samples is 55 percent. The average dry density is 65 pounds per cubic ft (pcf). The specific gravity in the surface sediment sample is 2.70, slightly higher than the specific gravity of 2.60 reported in the subsurface sediment sample. Friction angles obtained from the sediment samples ranged from approximately 33 to 43 degrees, while cohesion values ranged from 0 to 168 pounds per square foot (psf). At sample location RM13.5-G6, the angle of friction increased with depth from approximately 30 degrees to 40 degrees, and the cohesion decreased from 168 psf to 0 psf between the sampling intervals. The laboratory results further support the characterization of relatively low cohesive strength and granular nature of the sediment at RM 13.5. The unconfined compressive strength for the sediment tested resulted in a strength value of approximately 2.5 pounds per square inch. Based on this data, the cap consolidation is estimated to be between 0.75 inches (1.9 cm) to 1.5 inches (3.8 cm) after placement of the isolation cap, as presented in the Final FS, Appendix G (URS 2014). Geotechnical Characteristics of Adjacent Riverbank The riverbank adjacent to the RM 13.5 Study Area is generally characterized by steep riverbank slopes averaging 69 percent. The maximum slope measured at the RM 13.5 Study Area is greater than 100 percent (or 1 ft horizontal to 1 ft vertical [1H:1V]). No sandy beaches are present at RM 13.5; instead, the adjacent river shoreline is covered with large cobbles and riprap generally greater than 12 inches in diameter. The isolation cap starts at the toe of this riprap slope. Based on site reconnaissance along the riverbank during the FS Data Gap Investigation (URS 2013), slopes appear to be stable and are expected to remain stable based on the following observations: No areas of surface sloughing were observed where the slope surface was visible. Large portions of the slope faces are covered with berry bush and scrub brush, providing limited local reinforcement against sloughing.
2-5 SECTIONTWO Background
Upland reinforcement along the crest of the riverbank consists of concrete walkway and root structures of small trees and large shrubs. Recent excavation and installation of retaining structures, including landslide piers for the new Tilikum Crossing Bridge, serves to increase the overall stability of the slopes along the river bank.
2.4.3 Fluvial Setting and Bathymetry The surface water level in the Willamette River in the vicinity of the Study Area ranged from approximately 2.08 ft mean sea level (MSL) (7.1 ft NAVD 88) to 16.71 ft MSL (21.68 ft NAVD 88) (Morrison street gage, U.S. Geological Survey [USGS] 14211720) for measurements collected during the past 20 years. The highest surface water level occurred in February 1996 (420,000 cubic feet per second [cfs]) during the 1996 flood event. The lowest monthly discharge recorded during the past 20 years was 7,101 cfs in August 2001. The predicted 100-year flow in the Willamette River is 375,000 cfs and the corresponding water surface elevation is 31.73 ft NAVD 88 (URS 2014). The river discharge varies seasonally. The surface water level in the Willamette River is tidally influenced and is also affected seasonally by the recharge from stormwater and groundwater and flow within the Columbia River system. The median annual discharge for the Willamette River, recorded at the Morrison Street Bridge gage, is 26,600 cfs. The ordinary mean river surface water elevation within the Study Area is approximately 9 ft NAVD 88 at the adjacent riverbank. The maximum depth to the river is 39 ft, during ordinary mean water conditions, at a distance of approximately 80 ft west of the riverbank at the northwestern extent of the isolation cap area. At this location of the river, the river is approximately 1,400 to 1,500 ft wide and flows northwest. The river velocities at the RM 13.5 Study Area were collected during acoustic Doppler current profiler (ADCP) surveys conducted at RM 13.5 on July 26, 2013. The results of the ADCP survey indicated the surface velocities increased from the upstream transect toward the downstream transect. The average velocities in the RM 13.5 Study Area ranged from 0.5 ft per second near the riverbank to an average velocity of 0.7 ft per second near the western boundary of the Study Area. The surface velocity is similar to the velocity at the bottom of the river. The low velocities in the river in the Study Areas are conducive to a depositional environment. Under average flow conditions within the river, scour is not anticipated within the Study Area. The maximum near-shore (50 ft from the riverbank) velocities are predicted to be 4 to 5 ft per second within the study area. The maximum offshore velocities, predicted to be up to 7 ft per second during the 100-year event, were calculated to occur toward the center of the river. Maximum shear stresses for the same event were predicted to be under 0.34 psf. The erosive velocity and resulting shear stresses for RM 13.5 are presented in Hydrodynamic and Erosion Modeling at Study Areas RM 13.1 and RM 13.5 (Appendix B, URS 2014). The fluvial analysis is included herein as Attachment A-1.
2.4.4 Ecological Characteristics of Study Area A variety of plant, fish, bird, and mammalian species use the Willamette River, with the greatest diversity of fish (31 native fish species) in Oregon occurring in the Willamette River (Parametrix 2010). Numerous special status species use, or likely use, the Willamette River in some fashion. Special status is defined as a species (or its habitat) with regulatory protection under the federal Endangered Species Act (ESA), Oregon ESA, Oregon State Sensitive Species List, or Magnuson-Stevens Fisheries Conservation and
2-6 SECTIONTWO Background
Management Act, or that is identified as a Species of Concern by the Oregon Biodiversity Information Center. Due to the presence of special status species, the Willamette River is considered a sensitive environment as defined by Oregon Administrative Rule 340-122-115(50). The lower Willamette River (downstream of Willamette Falls) is considered critical habitat (rearing and migration) for lower Columbia River (LCR) and upper Willamette River steelhead distinct population segment (DPS) and Chinook salmon Evolutionarily Significant Units (ESUs). Critical habitat has been proposed for the LCR coho salmon ESU, but the designation has not been adopted. Although the portion of the Willamette River within the vicinity of the RM 13.5 Study Area has both deep water and shallow water components, the shallow water areas that are required for juvenile salmonid development and migration are limited by the lack of shallow water habitat complexity, absence of riparian vegetation, and heavy shoreline modification (i.e., dredging and replacement of the natural shoreline with rock revetment/riprap) to support commercial shipping. The greatest extent of shallow water habitat in the vicinity of the RM 13.5 Study Area is located along the western riverbank, opposite the RM 13.5 Study Area and adjacent to the Zidell property (Zidell 2012). Deep water habitat in the lower Willamette River is typically used by adult salmonids for upstream migration. Juvenile salmonids may use deeper water areas during out-migration and rearing, though they typically are found within the upper 10 ft of the water column. River traffic tends to limit the functionality and suitability of deepwater areas for juvenile salmonids (Parametrix 2010). Based on the draft Biological Assessment for the RM 13.5 Study Area (AECOM 2015a), five species of salmon and steelhead listed as “Threatened” under the ESA and managed by the National Oceanic and Atmospheric Administration Fisheries Service (NOAA Fisheries) are present within the lower Willamette River. Several plant and bird species were also identified as endangered or threatened under the jurisdiction of the U.S. Fish and Wildlife Service (FWS). The Biological Assessment reported that the individual and combined effects of all actions permitted are not expected to permanently impair currently properly functioning habitats, appreciably reduce the functioning of already impaired habitats, or retard the long-term recovery of properly functioning conditions.
2.4.5 River Use The Willamette River supports a full range of navigation, fishing, and recreational uses. Navigation uses range from non-motorized small boats (e.g., sailboats, canoes, kayaks, etc.) to ocean-going vessels. Fishing uses are supported from both limited public access points on the riverbanks, public docks, and from small watercraft. The Willamette River is open to both sport and subsistence (including Native American) fishing. Commercial fishing is allowed, although it is restricted to specific species and specific times of the year. In addition to boating and fishing recreation, the Willamette River is used for a range of recreational purposes, including water-contact recreation (e.g., swimming, water skiing, tubing, skurfing, etc.), sightseeing, birding, etc. Warnings against water contact recreation are issued by the City whenever rainfall is predicted or has occurred in amounts that could cause overflows from the Combined Sewer Overflow system. Willamette River banks above ordinary high water support a full range of urban recreational uses (e.g., walking, biking, and sightseeing). A company called Portland Spirit provides scenic river cruises from their private dock in the vicinity of RM 13.5. The Portland Spirit operation has five vessels actively using their docking facility. The vessel with the largest draw is the Portland Spirit, a 98 ft custom yacht with 3.67 ft diameter propellers and a maximum water draw of 8 ft. The vessels generally operate at a low speed and have a low torque. OMSI,
2-7 SECTIONTWO Background located just downstream of RM 13.5 and upstream of RM 13.1, rents a portion of their dock to anchor jet boats operated by Willamette Jet Boat Excursions.
2.4.6 Engineering Constraints Engineering constraints include utilities, overwater structures, limited access, limited in-water work windows, and transportation loading space for importing sand cap material. Several utilities are present within the in-water RM 13.5 Study Area (Table 1 and Figure 2), including the following: An active 20-inch-diameter pressurized gas pipeline An inactive 12-inch gas pipeline A 36-inch City water pipeline The gas pipelines are owned by NW Natural Gas Company and are constructed of metal piping inside a concrete sleeve. The 20-inch-diameter pressurized gas pipeline was installed in 1972 under an easement with the Oregon DSL. The pipeline was installed using a clamshell dredge for the excavation. The spoils were placed on the downstream edge of the excavation and used as backfill over the pipeline. The pipeline is buried approximately 6 ft bss. Currently, the pipeline crossing the Willamette River is under an easement that extends 100 ft on each side of the pipe centerline. Special work requests are needed from NW Natural to conduct work in the right-of-way altering the existing sediment surface; excavation within the easement is not allowed. Work within the NW Natural’s pipeline easement could cause consolidation of the underlying sediment, resulting in stress or damage to the existing pipeline. Therefore, as a precautionary measure, no work will be performed within the NW Natural pipeline easement. The inactive gas pipeline and City water line are outside the area to be capped. During installation of the sediment cap, no vessels will spud or anchor within 20 ft of the NW Natural pipeline. Due to the presence of a heavily used pedestrian and bike path at the top of a very steep and generally inaccessible bank along the entire length of the Study Area, access to RM 13.5 would be limited to over- water. In addition, the work will need to be completed in accordance with the approved work permits within the in-water work windows for the Willamette River, which extend from July 1 through October 31 and from December 1 through January 31.
2.5 Target Area One of the project RAOs for the RM 13.5 Study Area is to reduce the overall SWAC for the COCs and thereby reduce the overall risk to human health and ecological receptors (RAO 1). The Target Cleanup Area footprint for the isolation cap was determined for this RAO through an iterative exercise of extending the isolation cap over individual Thiessen polygon areas (above the CLs) and recalculating the resulting SWAC for each risk driver until the optimal Target Area was identified. The goal was to reduce the predicted SWAC for the Study Area to near or below the CLs while considering the existing environmental constraints in the Study Area. The existing engineering constraints are described in Section 2.4.6. The optimal Target Area for the isolation cap consists of 48,547 SF (1.11 acres) within the northern portion of the Study Area where the isolation cap will be placed (Figure 3). This area is located north of (outside of) the existing utility easements, including the NW Natural gas line easement for the 20-inch active natural gas line. Table 7 presents the baseline SWACs for the risk driver COCs, including total PCBs, dioxins/furans, and total DDx within the RM 13.5 Study Area and the estimated post-remedy SWAC immediately after active
2-8 SECTIONTWO Background remediation of the Target Area. Post-remedy SWACs are predicted to be very similar to the MUBCs. The estimated post-remedy SWAC values are calculated from the sum of a series of products of normalized Thiessen polygon areas and associated sediment concentrations. The post-remedy SWAC was calculated only for those polygons remaining outside of the cap Target Area where no remediation (installation of an isolation cap) is proposed, the baseline sediment concentrations were used (determined by sampling locations). The SWACs reflect Portland Harbor rules, including non-detected analyte group totals at the highest method detection limit.
2-9 SECTIONTHREE Basis of Design
3.0 BASIS OF DESIGN The selected remedial alternative at the RM 13.5 Study Area consists of placing an isolation cap over the Target Area, approximately 48,547 SF (1.11 acres), as described in Section 2.5. The purpose of the isolation cap is to prevent receptor exposure to the impacted sediments and also reduce migration (mobility) of the COCs in the underlying sediment within RM 13.5. The conceptual design components were presented in the Final FS (URS 2014). The isolation cap will be extended from the riverbank, from the toe of the rip-rap slope, across the river bottom to the limits of the Target Area. In general, fill slopes for the isolation sand layer and overlying gravel would be no steeper than 3 ft horizontal to 1 ft vertical (3:1) to maintain cap stability. The isolation cap Final Engineering Design plans are presented in Appendix B. Once the permits are issued for the RM 13.5 construction activities (see Section 4.1, below), the design drawings will be finalized for construction and submitted to DEQ under a separate cover letter. The following sections provide the specific details of the isolation cap design, specifically including the following: Isolation cap thickness Construction considerations Impacts to the community
3.1 Isolation Cap Thickness The isolation cap thickness is based on the following design components: Thickness required to achieve long-term chemical isolation of the contaminants Size of armor layer required to resist erosion Construction tolerances and allowances The initial thicknesses of each layer were based on a review of literature and guidance from similar sites. An appropriate thickness was refined for sand and gravel material based on site conditions and chemical breakthrough modeling to satisfy the site-specific design components.
3.1.1 Isolation Layer A cap isolation model (URS 2014) was used to estimate the time to achieve steady state flux conditions in the isolation cap layer and to predict the breakthrough time from the underlying sediment for select constituents into the upper 4-inch (10 cm) biologically active zone for the sand isolation layer (URS 2014). 1 The cap isolation model used a 1.96 ft (60 cm) chemical isolation layer of sand placed across the capped area. The sand would be natural Columbia River dredge sand, clean bank sand, or washed sand free of roots and other loose organic matter, trash, debris, snow, ice, or frozen materials with a minimum fraction of organic carbon of 0.1 percent with not greater than 10 percent passing the #200 sieve. The model assumed a reduction in the initial cap thickness due to the maximum predicted consolidation of 1.5 inches (3.81 cm) after placement. In addition, the overall thickness of the isolation layer may be reduced by up to 4 inches (10 cm) (URS 2014) due to mixing with the underlying bedded sediment during
1 Although the draft FS for Portland Harbor describes surface sediment as 30 cm based on active mixing zone depths, a 10 cm depth was used for cap modeling because the armor layer is 20 cm and will prevent vertical mixing.
3-1 SECTIONTHREE Basis of Design placement and still remain protective for the duration predicted in the isolation model at the surface of the sand layer of the isolation cap; however, sediment mixing is expected to be less than 1.2 inches (3 cm) based on observations at Zidell (Zidell 2012), where similar types of bedded sediment were encountered during the cap construction. The isolation cap model conservatively assumes the pore water concentrations in the sediment below the cap will remain at the concentration modeled without any depletion or degradation over time. The results also conservatively assume no natural deposition would occur above the placement of the sand isolation layer. Also, the cap model assumes the overlying armor layer does not provide any chemical isolation. Additional details of the cap isolation model are presented in Appendix G of the Final FS (URS 2014). The results of the modeling indicate a design life of the isolation layer ranging between 500 to 1,000 years for PCBs. The lowest estimate for the design life was calculated by using the maximum concentration of PCBs (Aroclor 1254) detected in surface sediment. The breakthrough time (time to reach 1 percent of the steady state concentration) for other constituents of potential concern and constituents of potential ecological concern were evaluated in the FS (URS 2014) and range from approximately 220 years to over 1,000 years, considering the most reasonable starting concentration and model input values for the surface sediment at RM 13.5. Among site constituents of potential concern, heptachlor epoxide, an insecticide metabolite with a lower organic carbon partition coefficient than the risk-driver COCs, resulted in the lowest estimated time to breakthrough of approximately 220 years, at which time the predicted pore water concentration within the upper 4 inches (10 cm; point of compliance) of the sand isolation layer is estimated to be 0.01 µg/kg, which is less than the MUBC of 6 µg/kg. The most likely breakthrough times for the other risk-driver COCs, using the mean input concentrations at RM 13.5, is approximately 1,000 years. In general, recontamination of the isolation layer would not occur from the underlying sediment or pore- water contribution during the expected design life of the cap, and a 1.96 ft (60 cm) isolation sand layer is sufficient for protection of surface sediment. The predicted reduction in the cap thickness related to potential mixing with underlying sediment and cap consolidation following placement (reducing cap thickness to 1.67 ft [51 cm]) will reliably limit risk to human health and environmental receptors in the future. A Long-Term Cap Inspection Monitoring and Maintenance Plan (IMMP) is described in Section 5.5.4 below. The IMMP indicates that cap monitoring and maintenance will be required on an as-needed basis in perpetuity. The IMMP describes a pro-active maintenance and repair program that provides long-term cap protection.
3.1.2 Armor Layer Design The purpose of the armor stone layer is to provide protection against erosional forces for the isolation cap. Three types of armor layer (over varying depth intervals) will be placed at RM 13.5, as determined by the type and magnitude of erosive force likely to impact each area/elevation of the cap: Cap Armor. The cap armor layer will be placed above the chemical isolation layer to provide resistance to erosion of the underlying chemical isolation layer. The cap armor will be placed below an elevation of +3 ft NAVD 88. The recommended armor layer consists of clean, coarse gravel, graded between 0.5 inches and 2.5 inches (1.3–6.3 cm) in diameter (median diameter of 1.5 inches [3.8 cm]) for protection from river scour and propeller wash. The gravel fill for the
3-2 SECTIONTHREE Basis of Design
armor layer will be placed across the sand isolation layer to an average thickness of 0.66 ft (20 cm) at a maximum design slope of 3H:1V. Shoreline Armor. The shoreline armor will be a 0.66 ft (20 cm) layer placed above the chemical isolation layer to provide resistance to erosion of the underlying chemical isolation layer along the shoreline. The shoreline armor will be placed above an elevation of +3 ft NAVD 88, abutting the existing rip-rap shoreline. The recommended armor layer consists of clean, coarse 2.5-inch (6.3 cm) angular gravel; this stone diameter will be protective of the infrequent vessel-generated wakes that will affect this elevation during low water conditions. The shoreline armor will extend beyond the eastern and southern extent of the sand isolation layer at a slope of 2H:1V. Toe Armor. Toe armor will be approximately 2.62 ft (~80 cm) thick at its thickest point and will consist of 3-inch (~8 cm) diameter stone. The toe armor will be placed in deep water just beyond the extent of the isolation cap to provide a structural base for cap stability and to provide erosion protection at the toe of the cap. The toe armor will be placed at a maximum slope of 2H:1V. The cap armor gravel design considered several factors that might induce cap erosion including waves, vessels, and current. Several different modeling scenarios were conducted to determine the armor stone diameter requirements to ensure long-term stability. Water Currents Design requirements for normal water currents and extreme flow events (100-year return interval) were determined based on the fluvial model results for the minimum stable particle diameters in the river during a 100-year flood event. The Hydrologic Engineering Centers River Analysis System (HEC-RAS) model, developed by the U.S. Army Corps of Engineers (Corps), was used to conduct the far-field, one- dimensional hydraulic analysis of the Willamette River. MIKE 21, a two-dimensional, free-surface flow modeling system, was used to calculate the near-field, flow velocity and bed shear stresses at RM 13.5. Under normal ebb tide conditions within the river, the velocities vary at RM 13.5 between 0.4 and 0.6 ft per second with a reasonable uncertainty in the mean velocity of 0.10 ft to 0.15 ft per second. The permissible shear stresses to resist scour under normal river conditions would be similar to those of fine colloidal sand, indicating there is currently a depositional environment in the RM 13.5 Study Area. Although small increases in the existing sediment surface elevation were documented between bathymetric surveys conducted in June 23, 2013, and in February 24, 2015, the increase in elevation was within the tolerance of the survey accuracy. No evidence of scour was present within the Study Area between these two bathymetric surveys. The fluvial model results are included as Appendix A-1a. The fluvial model was developed to predict the maximum velocity, or shear stress for which a particle of a given grain size would remain stable, where exceeding the velocity and shear stress could result in particle erosion within the river during a 100-year flood event. The predicted 100-year flow in the Willamette River is 375,000 cfs and the corresponding water surface elevation is 32.2 ft NAVD 88 (URS 2014). The results indicate the largest flood velocities are near the middle of the navigation channel and decrease near the shoreline. The maximum predicted river bottom velocities were 2.87 ft per second, as determined from the fluvial analysis approximately 60 ft from the shoreline within the cap target area (Appendix A-1a) where the cap armor will be placed. Table 8 presents conservative values for the permissible shear stress associated with different material types. Stable gravel armor for these river conditions should have a gradation between 1 to 2 inches. Table
3-3 SECTIONTHREE Basis of Design
8 shows a permissible velocity of 4 to 5 ft per second generates shear stresses between 0.33 to 0.67 psf, with the maximum of this range occurring near the center of the river in the Study Area. In this area, a mean gravel size of 1.5 inches (graded from 0.5 inches to 2.5 inches) was selected for the cap armor, where the velocities were approximately 2.87 ft per second. The predicted river bottom velocities (at an elevation of approximately -30 ft NAVD 88) closer to the center of the river are approximately 4 to 5 ft per second, as determined from the fluvial analysis conducted approximately 160 ft from the shoreline across the outer extents of the cap area (AECOM 2015c). For this area of the river, a larger toe armor, consisting of up to 3-inch (~8 cm) rock, will be placed. Capping guidance indicates the armor layer thickness should be a minimum of two times the diameter of the largest stone, resulting in a minimum armor layer thickness of 5 inches (~13 cm). An additional safety factor of 1.6 has been applied to bring the overall cap armor layer to a design thickness of 0.66 ft (20 cm). The armor layer size was selected to provide protection during a 100-year flood event. Additional monitoring and maintenance may be needed following 100-year flood events to ensure movement of the armor layers has not occurred, as well as assess the need for repairs. Since the smallest fraction of the gravel armor layer is 0.5 inch, some motion of the finer fraction may occur during 100-year flood conditions. However, under normal operating conditions, the cap armor layer gradation will be adequate for up to 100-year flood river velocities and limit the loss of the underlying chemical isolation layer. For added protection along the toe of the isolation cap that is nearer the middle of the river, the cap will key into a band of armor protection at the toe of slope to prevent lateral movement of the cap towards lower river elevations. Vessel Propeller Wash To ensure the cap armor layer design is protective of propeller wash, predictive equations were used to estimate the bottom velocity caused by propeller wash of several vessels operating in the area; specifically, commercial vessels operated by Portland Spirit Cruises. The propeller wash evaluation is included in Appendix A-2. The evaluation indicates a median stone diameter of approximately 0.5 inches (i.e., gravel) placed with a conservative thickness of 3 inches will resist anticipated propeller wash present in the Study Area. Therefore, the cap armor stone size (median stone diameter of 1.5 inch) and thickness (0.66 ft) is adequate to resist erosion caused by propeller wash conditions within the river. Institutional controls such as signage, restrictions to anchoring, and other controls are not recommended because the risk to the cap effectiveness is low, and long-term maintenance and repair BMPs will be implemented following construction of the isolation cap. Vessel-generated Waves The basis of design for sizing the shoreline armor also considered the potentially erosive forces of surface waves generated from a passing vessel. Two methods (Gates and Herbich [1977] and Sorensen [1997]) were used to estimate wake heights for vessels typically present along this stretch of the river. The first is typically used for self-propelled vessels, and the second is typically used for power-assisted vessels (wake shapes and propagations are different). Using output from these equation-based models, the Hudson’s equation was used to determine the stability of the shoreline armor stone with respect to wake generated wave forces along the shoreline (Corps 1995); these analyses are presented in Appendix A-3a and A-3b.
3-4 SECTIONTHREE Basis of Design
Several vessels operating in the vicinity of RM 13.5 were considered to determine the design wake height for the shoreline armor. Three vessel types were selected for analysis, each with at least one vessel transit per day. The largest known vessel traveling within the river is the Portland Spirit (commercial passenger vessel), which has a length of 150 ft, beam of 35 ft, and operational draft of 8 ft. The Portland Spirit typically docks near the RM 13.5 cap area, traveling within 200 ft of the cap area at a maximum velocity of 3 knots to the dock area, and typically completes between 3,000 and 4,000 trips per year. The Portland Spirit is estimated to produce an average wake height of 0.2 ft in the vicinity of RM 13.5 based on the Gates and Herbich (1977) equation, an appropriate method for self-propelled vessel wakes in deep water. The City of Portland fire rescue boat (fire boat) was the second vessel type evaluated. This vessel operates primarily in the navigation channel and has a length of 50 ft, beam of 15 ft, and draft of 4 ft. Based on conversations with the Harbormaster, the fire boat operates at minimum speed during routine patrols (once per day) to keep the wake well below 1 ft in height. Much less frequently, the boat may travel up to approximately 10 knots when responding to emergency calls; the City is responsible for any damage caused by the fire boat wake, and therefore the crew takes great care to minimize the vessel wakes (Ray Pratt, personal correspondence, August 17, 2015). Using an estimated speed of 10 knots, the fire boat would produce a maximum wake height of 1.3 ft. Under normal daily transit conditions, the maximum wake height would be closer to 0.7 ft. The Gates and Herbich method was used for self-propelled vessels operating in deeper water. Material barges (e.g., Ross Island sand and gravel material barges) were the third vessel type evaluated. Material barges more frequently operate within the navigation channel approximately 300 ft from the nearest edge of the cap area and generally have a maximum length of 100 ft, beam of 40 ft, and draft of 5 ft. Material barges are estimated to produce a maximum wake height of 0.7 ft, based on the dimensions of the largest anticipated barge moving at the highest anticipated velocity of 8 knots; this wake height was developed using the Bhowmik et. al method (Sorenson, 1997) applicable for towed barge vessels. Based on the various vessel types evaluated, the maximum estimated wake height near the RM 13.5 cap area is 1.3 ft, generated by the fire boat when responding to emergency calls. However, given the infrequent occurrence of emergency calls, the probability of occurrence is low, overly conservative, and not representative of typical conditions for the site. Instead, a design wake height of 0.7 ft was selected to account for the more frequent passage of material barges; this wake height accounts for the maximum barge size and speed in this reach of the river. The shoreline area will be inspected for stability as part of the long-term IMMP for the site. For armor stone sizing, the Hudson’s equation rock stability coefficient was selected to represent a minimum of two layers of angular armor stone and non-breaking wave conditions at RM 13.5. The calculations estimate a median rock weight of 0.63 pounds (equivalent to approximately a 2.1-inch rock) is sufficient to prevent significant armor layer movement due to a wake height of 0.7 ft. The shoreline armor design weight selected for RM 13.5 is 1 pound (equivalent to a maximum 2.5-inch stone [Corps 1984]). A more conservative rock size was not selected for RM 13.5 for the following reasons:
3-5 SECTIONTHREE Basis of Design
The Hudson’s equation provides a highly conservative estimate of armor stone size required to protect a shoreline. Armor size requirements are calculated assuming a repeated storm generated design waves over long periods of time, and assumes the armor layer must remain stable (rigid) at all times. Conversely, the RM 13.5 shoreline armor will be infrequently impacted by vessel wakes (e.g., 2-5 wakes per vessel), and occasional slight movement of the armor material is acceptable without undermining armor stability (best professional engineering judgment). Visual inspection of the Zidell cap (across the river from RM 13.5) indicates stability for their rounded gravel layer with a median diameter of 1.5 inches. The Zidell gravel layer (habitat layer) was installed over the same elevation range as the proposed shoreline armor layer for RM 13.5 on a shallow slope, and has remained stable since constructed in 2011. It has not experienced erosion. The proposed shoreline armor at RM 13.5 is larger in diameter and more angular than the gravel layer at Zidell, and therefore it should provide even more stability. The RM 13.5 shoreline armor will only be exposed during low water periods (e.g., summer months) and subjected to vessel-based wakes only during this time. Visual inspection of the Zidell shoreline shows that most of the erosion is occurring further up the slope at around ~+9 ft elevation (higher water periods). At RM 13.5, a robust rip-rap layer is present at this higher elevation. Deep-draft vessels infrequently use the navigation channel upriver of the Morrison Street Bridge at RM 12.8, because the navigation channel is not maintained throughout the Downtown Reach. The long-term monitoring and maintenance program requires visual inspection of the armor to evaluate armor stability and ensure the material remains protective against erosional forces over the long term. The IMMP is briefly described in Section 5.5.4.
Other Potential Erosive Factors Other potentially erosive factors that could affect cap stability include bioturbation and wind-generated waves. Bioturbation is defined as the disturbance and mixing of surface sediment by benthic organisms. Bioturbation depths are typically estimated by the type of species expected to colonize capping material and density. Bioturbation depth is often similar to either the depth of the biologically active zone or the active mixing zone depth determined for a site. A common method of conservatively estimating the lower extent of bioturbation is to examine those organisms present or likely to be present at the site. However, since RM 13.5 cap material will be fully armored, bioturbation of the isolation cap material is not expected. Erosion from wind-generated waves is determined by wave propagation due to winds, the size of the wave, and the length or fetch of the water body in which the wave is traveling. The project area is primarily exposed to wind-generated waves from the north-northwest in the summer months (low water level). Given the complexity of the water body geometry and the presence of many structures in the downtown reach of the river, a restricted fetch is expected. Based on visual observations across the river and along other shoreline areas, wind-generated waves are not expected to have a significant adverse effect on the shoreline armor at RM 13.5.
3.1.3 Construction Tolerances The sand fill for the isolation layer will be placed to an average thickness of 1.97 ft (60 cm) with an allowable margin of error of up to 10 percent (6 cm), resulting in a minimum allowable thickness of the
3-6 SECTIONTHREE Basis of Design isolation cap sand layer of 1.77 ft (54 cm) thick. The isolation cap thickness will not have an average overall thickness below the minimum thickness (1.77 ft) over more than 10 percent of the isolation cap area. No areas of the isolation cap sand later will be below an absolute minimum thickness of 1.67 ft (50 cm, which includes the estimate for consolidation and is the minimum thickness needed for chemical isolation). The gravel fill for the shoreline and cap armor layer will be placed to an average thickness of 0.66 ft (20 cm). The gravel armor layer will also have an allowable error in height during placement of up to 10 percent (2 cm) of the design elevation, resulting in a minimum thickness of 0.6 ft (18 cm) and a maximum thickness of 0.72 ft (22 cm). An electronic positioning system must be used to accurately locate and track the material placement during the construction of the isolation cap. The need for additional corrective maintenance to achieve the desired thickness following the installation of the cap will be determined from intermediate construction surveys and on an as-needed basis. Initial verification of the isolation capped area and total height of the cap material (before and after placement of armor layer) will be conducted by bathymetric surveys during installation. Cap thickness will be confirmed by sediment coring after placement of lift 1 and lift 2 of the isolation cap material. One final sediment core will be collected following placement of the gravel armor layer. The construction tolerance takes into account several processes such as chemical breakthrough times, flood control, consolidation of either the cap or underlying material, sediment core recovery, and bathymetry measurement accuracy.
3.2 Construction Considerations The isolation cap construction details were considered to improve the overall effectiveness of the cap. Specific details for the following components of the isolation cap construction were evaluated in more detail: the presence of existing debris in the proposed isolation cap area the material placement considerations engineering controls and water quality turbidity monitoring green remediation strategies
3.2.1 Debris Debris and objects were identified using the multi-beam survey with the backscatter analyzed during the June 23, 2013, multi-beam bathymetric survey (URS 2014). A follow-up debris survey was conducted by SolmarHydro on February 24, 2015. Larger debris items, including large woody debris, concrete, and rock outcroppings, were identified during the 2015 survey. Large debris within the cap footprint can potentially reduce the effectiveness of the cap by breaching the cap and causing additional scour at the surface. Large debris is considered to be anything with a height extending above the sediment surface of approximately 1 ft (30 cm) or more, and/or resting on the sediment surface and larger than 1 ft in any dimension. Identification of the surficial debris was confirmed via diver camera survey conducted between March 24 to March 26, 2015, to verify the dimensions and position of the identified debris. The results of these surveys are summarized in Appendix B, Figure F04.
3-7 SECTIONTHREE Basis of Design
It is necessary to identify and remove miscellaneous large debris protruding from or resting on the surface that may affect the long-term effectiveness of the isolation cap, before the isolation cap is placed. Items that are identified that extend more than 1 ft the sediment surface and that remain loose on the sediment surface (contact boundary between surface water and sediment) and not partially buried will be removed. Care must be taken during removal of the debris and objects to minimize suspension of sediment around or on the debris and objects. During removal, large debris extending above the sediment surface at a height greater than 1 ft will be cut at the mud line and the aboveground portion will be removed. The equipment used to remove the large debris must have sufficient reach and maneuverability to operate from a work barge (e.g., articulated claw, cable suspended crane, etc.). The large debris removal activities may require specialized equipment or diver assistance. The presence of small debris, wood chips, and piles below the sediment surface will add stability to the sediment below the cap (USEPA 2005); no debris removal is required for debris that is below the sediment surface.
3.2.2 Material Placement Considerations The cap material will be placed using a mechanical enclosed clam-shell bucket. To limit suspension and mobilization of the sediment, the clam-shell will be lowered and raised through the water column at a rate of no more than 1 ft per second to limit the potential for spillage and disturbance of riverbed sediments. During implementation, the bucket will be cracked open and allowed to spread evenly across the placement grid. It is anticipated that the sand and armor layer would be placed at a rate of approximately 400 to 800 cubic yards (cy) per day, based on experience at other local project sites including the Zidell project site (Zidell 2012). The actual production rate may vary; material placement may be slower near the riverbank where access is limited and repositioning may be more frequent. Potential weather delays and potential mechanical issues may require extra time. The clam-shell bucket will be equipped with a GPS to ensure accurate placement of the material. Corps guidance suggests a cap layer thickness of no more than 12 inches in a single application, to prevent uneven consolidation of the underlying material. Therefore, the cap placement will require a minimum of three lifts: two for the sand and one for the armor layer. Initial verification of the capped area and total height of the cap material (before and after placement of armor layer) will be conducted by bathymetric surveys during installation. Cap thickness will be confirmed by sediment coring after placement of lift 1 and lift 2 of the isolation cap material. Short-term effectiveness and constructability relies on gradual consolidation and increased bearing strength of the underlying material. The sediment at RM 13.5 has high water content and low shear strength, which requires slow daily production rates to avoid displacement or re-suspension of the underlying sediment. Slower production rates will also allow the cap materials to settle naturally between lifts and allow the weight of the cap to be spread across the sediment below the cap footprint to limit compression of the underlying sediment. Shortened fall distances are also important to avoid mobilizing the underlying sediment during placement. The primary consolidation of the cap material is expected to occur within hours after the material is placed. Building the cap gradually will increase the bearing strength across the entire area of the cap. The underlying material is expected to consolidate 0.7 to 1.5 inches (1.9 to 3.8 cm) following placement, assuming a relative density of the sediment to the overburden pressure of 0.25 to 0.3 percent (URS 2014). The stability of the cap also depends on the slope of the placed materials. Sediment caps generally placed on slopes no greater than 2.75H:1V are predicted to be stable (Palermo et al. 1998). Gentle slopes will
3-8 SECTIONTHREE Basis of Design also reduce the potential for sliding. The angle of friction at the RM 13.5 Study Area is estimated to be between 33 degrees and 43 degrees determined from plots of shear versus normal stress in the FS (URS 2014). Therefore, the design slope within RM 13.5 is conservatively specified to be 3H:1V, where achievable. Placement of additional material will be required in some areas of the cap to achieve the final specified slope and grade. Gas ebullition generation as a result of organic materials decomposing below the cap may occur but should be minimal at RM 13.5. Gas generation is unlikely to affect the stability of the cap because the permeability of the coarse sand and the gravel armor materials specified for the isolation cap will allow gas to dissipate naturally through the cap. The time required for complete consolidation of the subsurface is expected to be several months due to the presence of organic content within the subsurface sediment in RM 13.5.
3.2.3 Engineering Controls and Water Quality Turbidity Monitoring Debris removal in the RM 13.5 Study Area has the potential to produce floating debris, such as wood, as materials are brought to the surface. A floating debris boom will be installed around the work area to control potential floating debris generated during the debris removal activities. The 12-inch floating boom will be equipped with a standard mesh drop screen approximately 24 inches wide to capture and contain potential floating debris generated during the removal activities. All floating debris will be recovered from the upgradient side of the boom before the boom is removed. The removed debris will be consolidated with the other large debris generated during the removal activities for characterization and off-site disposal. Suspension of sand and sediment can happen in several ways during the construction phase of the remedial activities at RM 13.5, resulting in an increase in the total suspended solids (TSS) concentration in the surface water. In general, increases of TSS may occur from the following activities: Liberation of sediment from the objects during debris removal activities Loss of clean sand from the clam-shell while it is being lowered through the water column for placement Loss of clean sand while it is being placed above the sediment for construction of the isolation layer Re-suspension and mobilization of underlying sediment while clean sand is being placed above it The presence of fine-grained sediments in RM 13.5 indicates a normally low-energy environment where the river current velocities are low enough to allow fine particles to settle out of the water column. The normal river velocities in this area are between 0.5 and 0.7 ft per second at the river bottom, approximately half of the permissible velocity for fine non-colloidal sand cap material (Table 8). BMPs, including slow and gradual placement of the isolation cap materials, will be used to limit re-suspension and mobilization of the sediment as described in Section 3.2.2 above. The BMPs that will be used during material placement are described in Section 5.4 below. Elutriate tests were conducted to evaluate the potential for water quality effects during in-water work activities. The results of the standard elutriate test conducted during the FS sediment sampling event (URS 2014) indicated that an increase in the TSS concentration in the surface water did not result in an increase in the dissolved phase COC concentrations in surface water. However, increases in the TSS content in the water column would result in an increase
3-9 SECTIONTHREE Basis of Design in the turbidity of the water and an increase in the related risks to the aquatic system. Routine monitoring of the turbidity can provide information on naturally occurring trends in the turbidity compared to potential increases resulting from the construction activities. Therefore, turbidity monitoring will be required during the construction activities, in accordance with the permit, as an indicator of the water quality. The turbidity monitoring will be conducted in accordance with the permit requirements that meet Section 404 and 401 of the Clean Water Act. Turbidity monitoring requirements for the remediation work have been provided by NOAA Fisheries in a Biological Opinion addressing project activities (NOAA 2015). The turbidity requirements will be incorporated into the Nationwide Permit number 38 Decision Document issued by the Corps for the project. NOAA Fisheries requires collection of grab turbidity measurements for compliance every 2 hours during active construction at a representative upgradient and downgradient monitoring station (Table 9): The upgradient monitoring station will be located 175 ft upriver of the cap area. The downgradient monitoring station will be located 100 ft downgradient of the cap area. The downgradient monitoring station results must be up to and no higher than 10 percent higher than the upgradient (background) monitoring station results for compliance throughout construction. NOAA Fisheries also requires that work must be stopped and NOAA Fisheries must be notified if there are turbidity measurement results that exceed the compliance criteria of the compliance monitoring station reading measuring up to and no higher than 10 percent above the background measurement (in NTUs) . The monitoring requirements presented by NOAA Fisheries will be incorporated by the Corps into the final permit requirements, which may include additional turbidity monitoring requirements from the DSL and the DEQ. Appendix C also provides detailed monitoring requirements. The DSL will issue a General Authorization Eligibility Verification Form to document compliance with the Oregon State Removal-Fill Law (ORS 196.795-990). Copies of these approval documents will be submitted under a separate cover letter before construction begins at RM 13.5.
3.2.4 Green Remediation Strategies The procedures and goals for green remediation strategies will be established during the pre-construction meeting, with the input of the in-water construction contractor (IWCC), with the overall goal of reducing the green-house gas emissions, energy consumption, risk of accidents and injuries to workers, and waste generation during the construction. Some of these procedures may include operational hours of generators, boat idles, contents of tailgate safety meetings, and ways to improve safe work practices. SiteWise™ Tool (NAVFAC 2013) was used to predict the metrics for greenhouse gas emissions, total energy used, water consumption (on-site and total), mono-nitrogen oxides, sulfur oxides, and particulate matter up to 10 µm in size emissions and the potential for worker accident risk of injury that will be generated during implementation of the remedial action. The predicted results for these environmental footprint metrics are included in Appendix A-4. The actual metrics will be tracked during construction to determine the final actual environmental footprint and to evaluate and optimize processes during construction in an effort to reduce the environmental footprint. Sustainability-specific information will be recorded on the Daily Field Reports (DFRs) and used to track the environmental footprint throughout construction activities. This information will include hours of equipment operation, number of workers
3-10 SECTIONTHREE Basis of Design on-site each day, volume of material placed, and other resources, such as volume of water or waste generated on a daily basis. Optimization strategies will be implemented during construction to reduce greenhouse gas emissions, energy consumption, and waste generation, and may include the following:
Using clean and/or alternative fuels, such as ultra low-sulfur diesel or biofuel, and solar power to the maximum extent possible. Conducting daily equipment inspections and preventative maintenance for equipment to minimize downtime and reduce additional mobilization related to equipment repair. Minimizing equipment idling time to the maximum extent possible. Reducing daily travel for the crew by locating the staging area near the construction activities and implementing a car-pooling program. Minimizing waste generation by recycling recovered debris to the maximum extent possible and minimizing travel related to waste disposal. The actual metrics will be calculated following implementation using SiteWise and compared to the predicted metrics.
3.3 Impacts to Community The installation of an isolation cap may create short- and long-term impacts the community and surrounding area. Mitigation of potential impacts considered in the isolation cap design included reducing the risks to human health and ecological receptors; adhering to floodplain management requirements for no-rise; monitoring during construction to minimize the potential for construction- related impacts to the surrounding community; and limiting waterway use impacts.
3.3.1 Reduction in the Risk to Human Health and Ecological Receptors The main objective of the isolation cap is to achieve a reduction in the SWACs and reduce the overall risk to human health and ecological receptors. The project post-remedy SWACs were estimated and presented in the Final FS (See Appendix D in URS 2014). The resulting SWACs were developed considering installation of the cap over the most impacted areas within RM 13.5. No work will occur within the NW Natural gas line easement. As a result, sediments with COC concentrations above the screening criteria will be left unprotected in the easement area. To account for this limitation, the remedial action level (per DEQ request) was changed from the point-based concentration to the SWAC-based concentration. The resulting SWACs after the isolation cap is installed will be decreased by 89 percent from the baseline SWACs, calculated for total PCBs as Aroclors, total dioxins/furans TEQ for mammals, and total DDx. The baseline and predicted post-construction SWACs are presented in Table 7. The installation of the isolation cap will result in an immediate reduction of the SWACs in the sediment to concentrations protective of human health and ecological receptors. The total PCBs SWAC in the RM 13.5 remedial footprint is projected to decrease 89 percent from baseline SWAC of 50.6 µg/kg to 5.47 µg/kg total PCBs. The SWAC for total dioxins/furans is projected to be reduced from the baseline SWAC of 3.22 ng/kg to 0.86 ng/kg. The SWAC for total DDx is projected to be reduced below the MUBCs. The cap installation is an overall benefit to the human and ecological community.
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3.3.2 Adherence to Floodplain Management Requirements Since the isolation cap will be installed within the floodplain, an evaluation is required to ensure the standards of the floodplain management requirements are being met. A Federal Emergency Management Agency (FEMA) No-Rise study was performed to evaluate the floodway encroachment potential resulting from the isolation cap design. The results of the no-rise analysis are presented in the City of Portland No Rise Study Hydraulic Analysis Summary Report for RM 13.5 (AECOM 2015c) included as Appendix A- 1b. The FEMA No Rise requirement means there is no impact on 100-year flood elevations, floodway elevation, or floodway widths, which is defined by the City as increase in elevation of less than 0.005 ft. A pre-project conditions model was created to match the effective conditions model provided by FEMA. A proposed conditions model was developed from this pre-project conditions model. A comparison of these two models shows that the project will not increase the 100-year floodplain elevations in the project area or adjacent Willamette River reaches. An existing conditions model was developed for RM 13.5 and assumed a Manning’s roughness coefficient (n) value for the channel of 0.03, consistent with previous modeling done in the river. The analysis considered an isolation cap thickness of 2.62 ft or 80 cm (60 cm sand, covered by 20 cm of gravel). USGS Water Supply Paper 2339 (Arcement and Schneirder 1989) provides guidance on selecting Manning’s n values. For the armor gravel selected for the isolation cap, between 2 and 64 millimeters (0.08 to 2.5 inches), a Manning’s n value range from 0.028 to 0.035 is provided. The more conservative value of 0.035 was used in the analysis. The addition of the cap and scour protection increases the water surface elevation by less than 0.005 ft at the project site. A sensitivity analysis was conducted assuming the Manning’s n value for existing conditions was 0.025 resulting in a greater change in Manning’s n between existing and proposed conditions. The increase in water surface elevation due to the project was still less than the applicable standard of 0.005 ft. Flood storage compensation (balanced cut and fill) is required per the Portland City Charter (PCC) 24.50.060.F.8. As identified in the PCC, fill placed below the design flood elevation (32.2 ft NAVD 88) must be balanced with an equal or greater amount of soil material removal. Cut and fill quantities below the design flood elevation will need to be calculated and reported on the final as-built drawings for RM 13.5 plans. A flood hazard variance (PCC 24.50.070) was requested by PGE for use of the PGE Harborton Restoration project site, located at RM 3.2, as the location for the balancing cut. The RM 13.5 and Harborton projects both occur in the Willamette River FIRM Flood Zone AE, as required by PCC 24.50.060.F.8. The Harborton project will require the removal of approximately 180,000 cy of fill and native soils from within the 100-year floodplain of the Willamette River, well in excess of the estimated fill anticipated for the RM 13.5 isolation cap. The variance has been approved by the City in the Land Use Decision.
3.3.3 Impacts to the Community during Construction Work will be conducted within the waterway throughout the construction activities. The primary impacts to the community will be the presence of large work platforms and vessels in the waterway and the potential for construction noise and dust. The spudding locations within the RM 13.5 Study Area will be outside the cap area and coordinated with the boat captains operating boats from the Portland Spirit dock, to maintain an open waterway for the commercial vessels ingress and egress from the dock. Additionally,
3-12 SECTIONTHREE Basis of Design the Harbor Master will be notified of work activities within the waterway throughout the construction activities. During construction, the sound levels will be monitored on a weekly basis to ensure the sound levels are not a nuisance to the public and within the limits of the applicable City Ordinance levels of 70 decibels during normal working hours within the commercial district. Dust levels will also be monitored on a weekly basis to ensure that any dust generated from the construction activities is not above the 10 milligrams per cubic meter limit for inhalable particles at the boundary of the RM 13.5 work area.
3.3.4 Waterway Use Impacts The remedy will change the existing conditions along the northern half of the RM 13.5 Study Area by raising the sediment elevation slightly above the OLW elevation; however, as indicated above in Section 3.3.2, the bathymetric changes do not result in an adverse effect for the 100-year flood elevations or floodway widths. The river bottom elevation will be raised, with the lowest elevation, -27 ft NAVD 88, located in the northwest corner of the Study Area. PGE proposes to implement a long-term monitoring and maintenance program for the RM 13.5 isolation cap without implementing institutional control restrictions on the river use. The IMMP describes a pro- active maintenance and repair program to ensure long-term protection of the isolation cap. The upland property owners adjacent to the capped area will be advised of the presence of the cap. DSL owns the property located below the current OLW line, totaling 47,283 SF. OMSI owns the adjoining property located above the OLW line, where the remaining 1,265 SF of the cap will be placed. An easement with the DSL will also be obtained. The current and likely future recreational and commercial uses were also considered as part of the isolation cap design. Recreational activities consist of in-water boating and swimming activities since the shoreline is unsuitable for general recreational or commercial use. The cap design is offset approximately 50 ft from the main navigation channel and, therefore, boat traffic in the vicinity of the cap will be limited to ensure the protection of the isolation cap. The main navigation channel in the river will not be affected. The total depth of the water will be decreased by the thickness of the isolation cap, estimated to be up to 2.62 ft (80 cm), including the sand isolation and gravel layers of fill placed within the cap Target Area at the RM 13.5 Study Area. Installation of the isolation cap will also result in permanent alteration of critical rearing, migration, and foraging habitat. Impacts to critical habitat are expected to attenuate over several years as benthic organisms re-colonize the cap, and sands/sediments infill interstitial spaces in the gravel armor layer. Additionally, installation of the cap will result in the permanent improvement in the local and downstream environment as contaminants in the sediment are isolated from environmental receptors to limit their movement within the food chain, water column, and downstream sediments.
3-13 SECTIONFOUR Pre-Implementation Requirements
4.0 PRE-IMPLEMENTATION REQUIREMENTS The following sections describe the requirements to be completed before the project is implemented.
4.1 Permitting Requirements The following permits are anticipated for the project. DSL: o General Authorization for Minimal Disturbance within Essential Salmonid Habitat Waters o Access Agreement and Easement o Compliance with Oregon Removal/Fill Law (ORS Chapter 196) Corps: Joint permit application will include the following additional permitting documents for review by the National Marine Fisheries Service, DSL, and DEQ: o Oregon State Historic Preservation Office National Historic Preservation Act Section 106 Clearance o ESA Section 7 Interagency Consultations between the Corps and NOAA Fisheries Service/FWS o Clean Water Act Section 404 permit City: o Compliance with Portland City Code, Chapter 24.50 for construction in Flood Hazard Areas, issued in the form of a Land Use Approval Permit compliance would be achieved through substantially demonstrating substantive compliance with each of these permits (Corps, DSL, City, and DEQ compliance).
4.2 Project Monitoring Plans The project monitoring plans will be prepared before mobilizing to the RM 13.5 Study Area. Specific monitoring plans to be developed by the in-water construction subcontractor before mobilizing include the Site-Specific Construction Health and Safety Plan (CHASP) and the Construction Quality Assurance Plan (CQAP).
4.2.1 Construction Health and Safety Plan The top priority during implementation of the remedial action is to conduct all activities in a manner protective of workers, public, and the environment. The CHASP will include the following: Mechanisms for working safely in the project area and achieving safe working conditions for on- and in-water work activities Mechanisms for working around moving equipment, including a crane and other rotating and mechanical equipment Routine monitoring requirements for water quality, including turbidity
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Precautions for dust control Awareness of noise levels Requirements for personal protective equipment during project activities Requirements for decontamination of equipment and personnel The purpose of the CHASP is to assign responsibilities, establish personnel protection standards, establish mandatory safety operating procedures, and provide for contingencies that may arise while conducting the remedial activities. The subcontractor selected for the isolation cap construction will be responsible for their worker’s health and safety and all federal, state, and local health and safety laws. Rigid health and safety measures will be followed during the remedy implementation. All personnel performing duties will have met 29 CFR 1910.120 and 29 CFR 1926.65(e) 40-hour HAZWOPER training requirements, have a minimum of 3 days actual field experience under the direct supervision of a trained experienced supervisor, and be compliant with the 8-hour annual HAZWOPER refresher training requirements. Strict adherence to action levels and use of proper personal protective equipment, such as hard hats, safety-toed shoes, and life vests, will be followed during the remedial action implementation. Also, in the staging areas, stationary sources of dust (e.g., debris and/or cap material stockpiles) will be wetted, as necessary, to control the occurrence of windswept dust.
4.2.2 Construction Quality Assurance Plan Quality assurance and quality control (QA/QC) procedures are used to support the overall RAOs. The QA/QC procedures are outlined in the CQAP included in Appendix C. The purpose of the CQAP is to outline procedures and protocols to be followed to achieve the goals described herein. The CQAP outlines the project participants, the proposed data quality objectives, specific analytical methods, and QA/QC requirements that are necessary to support the overall RAOs. The CQAP helps the supervising managers, health and safety manager, and project participants ensure the project is conducted in a way to support the RAOs. Following the procedures outlined in the CQAP also ensures the data collected will meet the project needs and help ensure the project quality control steps are built into the project from the beginning. A Sampling and Analysis Plan (SAP) is included as an attachment to the CQAP. The SAP outlines the standard operating procedures for collecting and analyzing samples throughout the remediation activities. Potential samples may include sediment samples of cap materials for verifications and samples of remediation derived waste for characterization.
4.3 Pre-Implementation Data Requirements A bathymetric survey and a diver survey were performed to gather the additional physical data needed to finalize the construction plans and specifications for the RM 13.5 remedial action.
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4.3.1 Bathymetric Survey A bathymetric survey was conducted by SolmarHydro on February 24, 2015, to gather additional information for the final cap elevation design in the RM 13.5 Study Area. The data was evaluated to refine the following information: Locations of docks, support pilings, and piling spacing Pre-construction elevation of the sediment, surface water interface, and final placement elevation of the cap Edge of the riprap and riverbank Location of surficial debris in the RM 13.5 Study Area A high resolution multi-beam bathymetric survey of the Study Area was conducted during a period of high tide in order to get the best resolution and coverage. The bathymetric survey was completed to a horizontal and a vertical accuracy of 0.1 ft. The bathymetric survey data will be tied to the following datum: Horizontal Projection: North American Datum (NAD) 83/91 State Plane North Coordinate System Vertical Datum: NAVD88 The results of the sonar backscatter were also processed and used to characterize potential differences in sediment (e.g., density characteristics for the soil and identification of large obstructions).
4.3.2 Diver Survey Following the bathymetric survey in the RM 13.5 Study Area, a diver survey was conducted by Gravity Consulting, LLC from March 24 to March 26, 2015. The purpose of the diver’s survey was to identify the number, location, size, and type of large (> 1 ft) surficial debris within the RM 13.5 Study Area; and locate the GPS coordinates along the edge of the riprap and any obstacles present in the area where the top slope of the cap will meet the existing riprap. The diver’s survey provided a detailed list of the large objects present within the footprint of the isolation cap requiring removal during the project implementation. Contractors will identify the preferred method and equipment for removing the debris in their Work Plan.
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5.0 IMPLEMENTATION OF REMEDIAL DESIGN Implementation of the remedial design will occur during the in-water work window (July 1 through October 31). Specific details of the implementation are described in the following sections.
5.1 Project Management and Implementation Oversight Project management includes project coordination, agency meeting coordination, preparing and maintaining an accurate project schedule, field work oversight, and completion of progress reports during the remedy implementation. The project manager and field manager will coordinate the project components including construction schedule and work sequencing, designation of responsible personnel, construction quality control requirements, procedures for processing field decisions and change orders, procedures for processing applications for payment, submittal procedures and requirements, handling of record documents, use of the premises, permits and approvals, office, work, and storage areas, equipment deliveries and priorities, safety, first aid, security, working hours, and property access. The project manager and field manager will coordinate with Chris Bozzini, the PGE Project Manager, and Dave Lacey, the DEQ Project Manager, as necessary through the duration of the project. All required documents, including, but not limited to, the CHASP, DFRs, permits, and waste handling and transportation documentation will be stored at a designated location for the project (field office). The document storage location will be accessible to all management personnel and readily accessible to all personnel upon request. DFRs will be completed by the field manager each day work is performed at RM 13.5. A copy of the DFR form is included in Appendix D. The DFR will include the following information, at a minimum: 1. Summary of activities performed for the day 2. List of subcontractors working in the Study Area 3. Personnel present and daily worker utilization 4. Condition of and any repairs made to the environmental controls 5. Use and condition of project-related equipment 6. Any accident or near miss reported (See CHASP Reporting Forms) 7. Meetings and significant decisions 8. Unusual events and/or regulatory agency or official inspections (provide name, contact information, nature of visit and any concerns/issues noted, and Contractor plan to rectify any issues) 9. Stoppages, delays, shortages, and losses 10. Emergency procedures 11. Any problems encountered and their proposed resolution 12. Status of the schedule 13. Requests for Information and/or Change Orders received and implemented 14. Excavation change directives received 15. Results of water quality monitoring 16. Manifest for materials placed in or removed from the Study Area 17. List of photographs collected during the work 18. Other relevant documentation (permits, records of inspections, etc.)
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Evidence of safety meetings will be submitted with DFRs and maintained in the project file throughout the duration of the project. A copy of an example Daily Safety Tailgate Meeting Form is included in Appendix D. HME Construction, Inc., PGE’s IWCC for the isolation cap, will develop the final Daily Safety Tailgate Meeting Form for the project for PGE’s approval, before beginning the construction activities. Copies of the DFRs will be submitted to the PGE and DEQ project managers via email on a daily basis. The DFRs will be assembled on a weekly basis, with any outstanding paperwork such as waste manifests and survey results, and submitted to the PGE project manager via PGE’s Portland Harbor SharePoint website.
5.2 Mobilization Mobilization for work in the RM 13.5 Study Area consists of verifying the cap material sources, establishing equipment and materials staging areas, establishing work facilities including a temporary field office, conducting utility clearance along the riverbank and Study Area, and installing the necessary engineering controls before beginning the construction of the isolation cap.
5.2.1 Isolation Cap Material Verification The isolation cap materials, consisting of sand and gravel as specified in the Final FS Report (URS, 2014), will be obtained from Knife River Materials, Waterview Pit in Columbia City, Oregon, located approximately 30 miles from the site. All material must be verified and approved following verification by PGE before the material is mobilized to the RM 13.5 Study Area. The capping material identified for use from the Waterview Pit is coarse sand that was dredged from the Columbia River as part of the channel deepening project between Longview, Washington, and Rainer, Washington. The cap armor gravel is sourced from the Waterview Pit. Additional material sources may be used for the gravel source, depending on the final quantities and size requirements. The sand and gravel specified for the cap will consist of imported material and will be free from roots and other loose organic matter, trash, debris, snow, ice, or frozen materials. A verification letter from the representative of the gravel fill sources will be provided to indicate the material is from a naturally placed source. Samples of the sand fill material source will be obtained and tested for the site-specific COCs. The chemical and physical testing requirements for the sand fill source are presented in the CQAP (Appendix C). Verification testing will also comply with any additional testing requirements that may be specified in the Corps’ joint permit.
5.2.2 Equipment and Material Staging An upland staging area will be required to offload debris recovered during debris removal activities (if needed) and store debris until characterized for off-site disposal. A staging area is also required to stockpile clean sand and gravel materials for the isolation cap. In addition, an upland storage area can be used by construction subcontractors to stage unused equipment and for a field office during the construction activities. The upland staging area will require water access to accommodate up to two barges and an accessible dock area used to transport materials and equipment (crane, etc.) from the staging area to the barge. The final staging area and staging details will be identified for the project following selection of an in-water construction subcontractor.
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5.2.3 Utility Clearance Utility clearance will be conducted as part of the mobilization activities. Oregon’s utility-locating agency will locate, identify, and mark all utilities in the vicinity of the Study Area, including the NW Natural gas line, the City stormwater outfall, and the City water main located in proximity to the isolation cap footprint. The existing utilities will be protected from damage throughout the remedial activities. Proper notification will be provided to the owner of the utility if any damages do occur and repairs will be made in accordance with federal, state, and local requirements. Utility markings will be made along the top of the riverbank. Alternatively, representatives of each utility will meet on-site to provide current information about the locations of their utilities.
5.2.4 Installation of Engineering Controls Engineering controls will be employed at RM 13.5 to limit sediment disturbance during installation of the sediment cap. Controls include installation of a floating boom, survey control points, baseline water quality measurements, and BMPs.
Floating Boom. A 12-inch floating debris boom will be installed around the work area to control potential floating debris generated during the debris removal activities. This boom will be installed to facilitate recovery of floating debris or any debris breaking free during the debris removal activities after the baseline conditions of the Study Area have been established. Survey Control Points. Survey control points will also be established in the Study Area, along the riverbank, by a licensed surveyor before beginning capping activities within RM 13.5. The control points will serve as the baseline for the horizontal position and vertical elevation control throughout the project. The control points will be aligned with the control points used for the pre-construction bathymetric survey conducted in the Study Area. The specific control points will be tied to existing City benchmarks. Baseline Water Quality Measurements. Baseline water quality will be established prior to construction activities at the RM 13.5 Study Area using turbidity measurements at two monitoring locations: an upstream monitoring station and a downstream monitoring station. The upriver station will be located approximately 175 ft upstream of the isolation cap area and the downriver monitoring station will be located 100 ft downgradient of the isolation cap area. The turbidity measurements will be collected from the midpoint of the water column (as measured during low-tide), estimated to be approximately 17 ft deep. The monitoring equipment is presented on Figure F08 in Appendix B and includes the following: Two (2) cellular data buoys (150 pound buoyancy) with batteries, solar panels, and cages Two (2) YSI turbidity sondes with built-in wiper The data buoys will be moored with a chain and anchor system and equipped with an LED marine beacon for signaling within the waterway. A web datacenter will be established and real-time turbidity data will be collected throughout the remedial activities in accordance with the permit requirements. Additional requirements of the water quality monitoring program for the remedial activities are described in the CQAP (Appendix C). Data will be collected at hourly intervals at each buoy location for a minimum of two 10-hour days before work is conducted in the RM 13.5 Study Area, to establish baseline conditions at RM 13.5. A calibration test will also be conducted, during the baseline data collection, to verify the placement of the water quality monitoring stations is representative of the river conditions.
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A turbidity curtain is not recommended for cap installation at RM 13.5 for the following reasons:
The curtain depth may be as deep as 38 ft at the mean water elevation, which requires a closely spaced anchoring system for a type II turbidity curtain. The installation of the anchoring system would disturb the bedded sediment in the vicinity of cap target area during the cap installation. The proximity of the curtain within the work zone conflicts with the maneuvering area requirements of the barges and work platforms anticipated for the cap installation. The use of a turbidity curtain would add up to 10 working days in the construction schedule (currently estimated to be 22 days without the curtain) to install, maintain, and remove the curtain.
5.3 Debris Removal Debris removal activities can begin in the RM 13.5 Study Area after the engineering controls, including debris boom and water quality monitoring stations, are in place.
5.3.1 Debris and Object Recovery Debris removal will be accomplished by a crane or excavator with sufficient reach and maneuverability to operate from a work barge (e.g., articulated claw, hydraulic grapple, etc.), but may require diver assistance or other specialized equipment. Equipment and methods will be selected to minimize re- suspension of sediments during debris removal. The water quality upgradient and downgradient of the construction area will be monitored during the debris removal activities to ensure it remains within permitted limits. A list of the debris identified in the isolation cap footprint from the bathymetric survey, conducted on February 24, 2015, and the diver debris survey conducted between March 24 and March 26, 2015, is presented in Appendix B, Figure F04. Large woody debris identified for removal that extends into the sediment will be cut off at the mud line by hand using a diver or using hydraulic snips, leaving the buried portion to be covered under the cap. The unburied portion will be removed for proper disposal or salvage. The debris and objects recovered will be transferred from the water to a water-tight barge or roll-off box. The recovered debris will be transported to HME’s watertight dock off-loading area, located at 6801 NW Old Lower River Road in Vancouver, Washington, where the material will be transported for disposal or salvaged following profiling. Equipment coming in contact with the impacted sediment during the debris removal and management activities will be decontaminated in accordance with the requirements presented in the CQAP (Appendix C.)
5.3.2 Waste Management Waste debris, such as scrap metal, concrete, sediment, and small woody debris, will be consolidated into roll-offs or drums. The waste material will remain on barges at the HME dock, until profiled for disposition, then directly off-loaded for transportation to the salvage or disposal facility. The waste material will be sampled in accordance with the requirements described in the CQAP (Attachment C). Following characterization, the waste will be profiled. Decisions regarding the final disposition for the waste materials generated will be made according to all federal, state, and local requirements. Following
5-4 SECTIONFIVE IMPLEMENTATION OF REMEDIAL DESIGN determination of the appropriate disposition, the waste materials will be transported for disposal at a licensed disposal facility. If possible, waste meeting the Oregon’s Recycle Laws and DEQ’s green remediation policy, finalized in November 2001, will be segregated to promote and support sustainable practices and to recognize the environmental benefits of waste prevention, reuse, and recycling.
5.4 Cap Installation The isolation cap will be installed over approximately 48,547 SF (1.11 acres), as shown in Appendix B, Figure F05. The isolation cap design consists of a 1.97 (60 cm) thick sand isolation layer overlain by a 0.66 ft (20 cm) thick protective gravel armor layer. Design cross sections of the cap are shown in Appendix B, Figure F07, and the isolation cap details are presented in Appendix B, Figure F08. The cap installation will result in approximately 6,650 cy of permanent fill being placed within the cap footprint in the river.
5.4.1 Material Placement Bulk cap materials, including clean sand and gravel, will be delivered to the site by a barge, which will be secured during work with a temporary pile anchor system (spudding). The cap materials will be carefully placed using a conventional clam-shell bucket deployed by a crane working from a second barge with material placed in approximately 1 ft lifts or less. BMPs that will be used to limit sediment disturbance during installation of the sediment cap include placement of small batches (up to 10 cy) of material in shallow lifts (less than 1 ft increments) in a slow and controlled manner using a clam-shell bucket that will be released up to 5 ft below the water surface during placement. The slow river velocity and depth of the water column at RM 13.5 facilitates natural and uniform gentle settlement of the clean (low content of fines) sand fill via gravity, with very low kinetic energy as the clean fill comes in contact with the river bottom. This same method of placement has been proven to effectively minimize the disturbance of riverbed sediments and mitigate sediment suspension and mobilization at similar capping sites, specifically including Zidell (Zidell 2012), located in close proximity to RM 13.5.
The following BMPs will be followed during placement of the cap materials to minimize disturbance of the sediment:
A clam-shell or other debris removal equipment will be operated at a rate of no more than 1 ft per second when raising or lowering through the water column to reduce the potential for spillage and disturbance of riverbed sediments. The motion of the clam-shell or other debris removal equipment will be paused after the recovered debris breaks the water surface. Items may potentially be removed by hand by divers to minimize suspension of sediment in the water column. Cap material will be placed in lifts of 1 ft in height or less. Cap isolation layer and overlying armor will be placed at a design slope of 3H:1V across the cap target area. The overlying armor will be placed at a slope of 2H:1V at the boundary of the isolation cap area, where the elevations are graded to meet the existing elevation of the bedded sediment.
5-5 SECTIONFIVE IMPLEMENTATION OF REMEDIAL DESIGN
If turbidity exceedances are observed during construction, then additional BMPs will be required (e.g., slower bucket cycle times, longer bucket sweeps). The cap will be constructed beginning at the lowest elevation (deeper water) and working up the slope filling in gridded areas along transects to the highest elevation. Some mixing of the sand placement material with the underlying bedded sediment is expected. Sediment cores will be collected following placement of the first two 12-inch sand lifts to assess mixing between the sand layers and the bedded sediment and cap thickness. The sediment core results will be evaluated and if deficiencies in the cap thickness are apparent, then the need for additional fill material will be evaluated, in combination with the bathymetric survey, to ensure the design thickness of the cap is met. Sediment cores are described in Section 5.4.3. The cap will be installed to maintain a design slope of 3H:1V. Cap material will not be compacted; consolidation will be allowed to occur through natural settlement. The isolation cap sand layer will be placed across the entire cap footprint before the gravel armor layer is placed. A multi-beam bathymetric survey will be completed following installation of the isolation cap sand layer, before placement of the gravel layer, to document the thickness of the isolation cap sand layer.
5.4.2 Water Quality Monitoring During Construction Water quality monitoring will be conducted in accordance with the permit requirements, identified in the Water Quality Certification, that meet Section 404 of the Clean Water Act. Water quality will be monitored throughout the construction activities at the RM 13.5 Study Area using turbidity measurements at two monitoring locations: an upstream monitoring station and a downstream monitoring station. The upriver station will be located approximately 175 ft upstream of the Target Area and the downriver monitoring station will be located 100 ft downgradient of the Target area. The turbidity measurements will be collected from the midpoint of the water column, estimated to be approximately 17 ft deep above the river bottom. Turbidity readings will be collected from data buoys moored at the designated upstream and downstream stations with a remote web datacenter for evaluating real-time turbidity data. Data will be collected at hourly intervals and will be reviewed throughout the remedial activities in accordance with the permits. Additional requirements of the water quality monitoring program for the remedial activities are described in the CQAP (Appendix C).
5.4.3 Sediment Cores and Confirmation Surveys Bathymetric and diver surveys will be used as the primary methods of identifying deficiencies that would trigger the need for placement of additional capping material. In addition, sediment cores will be collected within the cap footprint to provide additional information to qualitatively assess mixing thicknesses of the fill and bedded sediment. The following sediment cores will be collected at RM 13.5: Four (4) sediment cores will be collected following placement of the initial 1ft lift of coarse sand fill. Two (2) sediment cores will be collected following placement of the second 1ft lift of coarse sand fill. One (1) confirmation sediment core will be collected if feasible, following placement of the gravel armor layer and completion of the cap.
5-6 SECTIONFIVE IMPLEMENTATION OF REMEDIAL DESIGN
Bathymetric and diver surveys will be conducted to visually inspect the cap material placement and ensure the cap is placed across the intended area and at the intended thickness while the engineering controls are still deployed. A description of the sediment core collection and confirmation survey requirements is presented in the CQAP (Appendix C). If any deficiencies are noted during the initial confirmation survey, then additional fill placement will be evaluated to ensure the isolation cap meets the design criteria. The confirmation surveys are expected to take no more than 3 days to complete and would be accomplished by a survey vessel operating in the project area. Bathymetric surveys, including the pre- construction survey, an intermediate survey following the placement of the isolation cap sand layer and the post-cap construction survey following placement of the armor layer, will be reviewed by the Project Engineer. Divers will use the survey vessel as a work platform from which to carry out survey activities. Removal or fill activities are not proposed for the confirmation surveying activities at this time, though deficiencies in cap installation may necessitate further in-water construction to ensure proper cap installation.
5.5 Restoration The restoration activities for the remedial action include removal of the engineering controls, post- construction cap monitoring and maintenance, and final reporting to document the construction activities.
5.5.1 Removal of Engineering Controls Equipment will be demobilized from the project area (e.g., barges, etc.) and the water quality monitoring stations will be deactivated and removed following cap installation, confirmation of cap thickness, successful completion of the post-construction surveys, and acceptance of the survey following review and approval by the Engineer. Removal of engineering controls should take no more than 3 days to complete and involves the removal of all temporary fill elements, such as anchors that will be used to secure the water quality monitoring stations and debris boom, identified in the Corps joint permit application.
5.5.2 Post-Construction Cap Monitoring and Maintenance Post-construction monitoring will follow successful installation of the isolation cap. The post- construction monitoring will consist of a second post-construction survey conducted after a period of 6 months to document cap stability. The primary goal of cap monitoring after 6 months is to verify the cap integrity and thickness. A bathymetric survey will be conducted to determine the elevation of the sediment at the time of the monitoring event. The results of the bathymetric survey will be compared to the post-construction bathymetric survey to identify discrete areas where deposition or erosion has occurred and to identify the overall consolidation of the cap following placement and settlement. The cap integrity and thickness may be compromised as a result of erosion, floods, burrowing animals, or other miscellaneous actions or events within the waterway; therefore, a diver survey will also be completed to inspect the surface of the cap for any visible deficiencies. The restoration of the bioturbation zone and presence of newly deposited sediment will be qualitatively evaluated from video collected during the diver survey. Indicators of bioturbation will include observations of benthic activity within newly deposited sediment.
5-7 SECTIONFIVE IMPLEMENTATION OF REMEDIAL DESIGN
Cap maintenance may be required if deficiencies are identified within the cap or if the armor layer has been compromised. Areas where a significant elevation loss is noted may be indicative of settlement or erosion. If, after a visual inspection and bathymetric survey, greater than 90 percent of the cap area is at or above the as-built surface elevation, then no maintenance action will be necessary and the monitoring schedule will remain the same. However, if the compromised area covers more than 10 percent of the overall capped area, then a follow-up evaluation of the appropriate cap maintenance will be determined. If appropriate, larger diameter armor may be re-placed in areas where the armor layer has been compromised, thereby to returning cap function to the intended design. Event-based monitoring will also be conducted on an as-needed basis after extreme events (e.g., flood events, significant earthquake, etc.). Long-term monitoring and maintenance, including event-based monitoring, is described in Section 5.5.4 below and will also be described in the Construction Completion Report (CCR) following implementation of the remedial design.
5.5.3 Construction Completion Report The CCR will be prepared following implementation of the remedial action at the RM 13.5 Study Area. The field activities will be documented in the CCR within 90 days following completion of the isolation cap construction activities. The CCR will include the following, at a minimum: A detailed description of the work completed at the RM 13.5 Study Area An explanation of any changes to the work defined in the Final RD Report, including as-built drawings of the isolation cap and an explanation of why the changes were necessary and beneficial to the project A summary of the analytical results generated for fill verification and waste profiling A summary of environmental field data generated during construction activities, including turbidity monitoring results and results of the sediment cores Pre-and post-construction bathymetric survey results and post-construction diver survey results with figures depicting changes in the surface elevation Summary of final placement thicknesses for the isolation cap and the total removal and fill volumes Copies of all waste manifests A field photograph log Green and sustainable remediation quantities A description of outstanding items, such as the 6-month post-construction cap monitoring and maintenance event and preparation of the Final IMMP
5.5.4 Long-Term Inspection Monitoring and Maintenance Plan A copy of the Draft IMMP is included as Appendix E. The Final IMMP will be prepared following implementation of the remedial action at the RM 13.5 Study Area and following the implementation of the 6-month post-construction confirmation surveys.
5-8 SECTIONFIVE IMPLEMENTATION OF REMEDIAL DESIGN
The IMMP describes the project background, outlines specific inspection monitoring requirements, describes project-specific QA/QC procedures that will be applied to the monitoring activities, and describes the project documentation that will be completed to demonstrate that the long-term compliance goals are being maintained for the remedial action, as specified in the ROD. The Draft IMMP also describes the decision criteria and procedures that will be used to determine if additional maintenance is required. The Final IMMP will be submitted as an Appendix to the Final CCR.
5-9 SECTIONSIX PROJECT SCHEDULE
6.0 PROJECT SCHEDULE The proposed project is scheduled for implementation in summer 2015 during the Oregon Department of Fish and Wildlife in-water work window, with follow-up surveys occurring outside the in-water work window in spring 2016. The anticipated schedule for all project activities is as follows:
Task Scheduled Task Start End Duration # (Tasks are Sequential) (Date) (Date) (Days) 1 Project Permitting: Feb‐15 Aug‐15 180 2 Isolation Cap Construction: Sep‐14 Oct‐15 31 2a Mobilization Sep‐12 1 2b Installation of Engineering Controls and Baseline Monitoring Sep‐14 2 2c Debris Removal Sep‐14 5 2d Cap Installation Sep‐21 23 3 Post-Construction Activities: Oct‐19 Oct‐28 7 3a Post-Construction Surveys Oct‐19 3 3b Removal of Engineering Controls Oct‐22 3 3c Demobilization (Following approval of substantial completion by PGE) Oct‐28 1 4 Long-Term Monitoring and Maintenance Requirements Nov‐15 Apr‐16 210 4a Construction Completion Report (90 Days After Demobilization) Nov‐15 90 4b 6-Month Bathymetric and Diver Survey (180 days after Project Time 0) Apr‐16 16 4c Long-Term Inspection Monitoring and Maintenance Plan Nov‐15 5
A detailed project schedule, with the proposed construction activities and final permitting deadlines, is included as Figure 5. The schedule may change as the project progresses.
6-1 SECTIONSEVEN References
7.0 REFERENCES AECOM. 2015a. Biological Assessment for River Mile 13.5 Remedial Action, Multnomah County, Oregon. January 2015. ———. 2015b. Draft Remedial Design Report for River Mile 13.5, River Mile 13.5 Willamette River, Portland, Oregon. February 19, 2015. ———. 2015c. City of Portland No Rise Study Hydraulic Analysis Summary Report – RM 13.5. June 2015. Arcement, G., and V. Schneirder. 1989. Guide for Selecting Manning’s Roughness Coefficients for Natural Channels and Flood Plains. United States Geological Survey Water – Supply Paper 2339. Corps (U.S. Army Corps of Engineers). 1984. Shoreline Protection Manual. Coastal Engineering Research Center. U.S. Department of the Army. 1984. ———. 1995. Design of Coastal Revetments, Seawalls, and Bulkheads. EM 1110-2-1614. June 30, 1995. DEQ (Oregon Department of Environmental Quality). 2009. Downtown Portland – Willamette River Sediment Evaluation – Preliminary Identification of Locations of Interest. Oregon Department of Environmental Quality, October 13. ———. 2012. Letter from Tom Gainer, Oregon Department of Environmental Quality to Richard George, PGE, Regarding Order on Consent for PGE Willamette Project, ECSI #5249. DEQ No. LQVC-NWR-12-07 Order on Consent for Feasibility Study and Source Control Measures. July 16, 2012. Gates, E.T. and J.G. Herbich. 1977. Mathematical Model to Predict the Behavior of Deep-Draft Vessels in Restricted Waterways. TAMU-SG-77-206. 1977. NOAA (National Oceanic and Atmospheric Administration). 2015. Letter from William W. Stell Jr. to Shawn H. Zinzer, U.S. Army Corps of Engineers, Regarding Endangered Species Act Section 7(a)(2) Biological and Conference opinion, and Magnuson-Stevens Fishery Conservation and Management Act Essential Fish Habitat Response for Portland General Electric’s River Mile 13.5 Remedial Action, on the Willamette River (HUC 170900120202), Multnomah County, Oregon (Corps No.: NWP-2015-40), May 12, 2015. NAVFAC. 2013. SiteWise™ Version 3 User Guide, UG-NAVFAC-EXWC-ENF-1302. Naval Facilities Engineering Command, Engineering and Expeditionary Warfare Center. Prepared by Battelle Memorial Institute. July 2013. Palermo, M. R., Miller, S. Maynord, and D. Reible. 1998. Assessment and Remediation of Contaminated Sediments (ARCS) Program Guidance for In-Situ Subaqueous Capping of Contaminated Sediments. EPA 905/B-96/004. Prepared for the Great Lakes National Program Office, United States Environmental Protection Agency, Chicago, Illinois. Website: http://www.epa.gov/glnpo/sediment/iscmain. Parametrix. 2010. South Corridor, Biological Assessment for the Portland-Milwaukie Light Rail Project, Final. Prepared for Tri-County Metropolitan Transportation District of Oregon (Tri-Met) and Metro. October 2010.
7-1 SECTIONSEVEN References
Sorensen, R.M. 1997. Prediction of Vessel-Generated Waves with Reference to Vessels Common to the Upper Mississippi River System. Prepared for U.S. Army Corps of Engineers. 1977. USEPA (U.S. Environmental Protection Agency). 2000. Institutional Controls: A Site Managers guide to identifying, evaluating, and selecting institutional controls at superfund and RCRA corrective action cleanups. OSWER 9355.0-74FS-P. EPA540-F-00-05. September. ———. 2005. Contaminated Sediment Remediation Guidance for Hazardous Waste Sites. Website: http://www.epa.gov/superfund/health/conmedia/sediment/guidance.htm URS. 2010a. Preliminary Assessment for River Mile 13.1 – 13.5 Drainage Areas, Final. May 7, 2010. ———. 2010b. Data Report, Portland General Electric, Willamette River Sediment Investigation, River Miles 13.1 and 13.5. Prepared for Portland General Electric Company, Portland Oregon by URS for submittal to Oregon DEQ. June 16, 2010. ———. 2011. Final Sediment Remedial Investigation Report River Miles 13.1 and 13.5, Willamette River, Portland, Oregon. Prepared for Portland General Electric Company of Portland, Oregon by URS, for submittal to Oregon DEQ. December 2011. ———. 2013. Final Feasibility Study Work Plan for River Miles 13.5 and 13.5. Prepared for Portland General Electric Company. February 2013. ———. 2014. Final Feasibility Study for River Miles 13.1 and 13.5, Willamette River, Portland, Oregon. Prepared for Portland General Electric Company by URS. November14, 2014. Zidell. 2012. Construction Completion Report. Zidell Bank and Sediment Remediation Project. Zidell Waterfront Property, 3121 SW Moody Avenue, Portland, Oregon. ECSI No. 689. Prepared for ZRZ Realty Company. Prepared by Maul Foster & Alongi, Inc. April 26, 2012.
7-2 FIGURES
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0 FIGURE 4 7 9 6 5 2 \ : K PGE RM 13.5 Remedial Action Schedule ‐ Design/Construction ID Task Name Duration Start 2016 FebruaryMarch April May June July August SeptembeOctober NovembeDecembe January February March April May June July August SeptembeOctobe B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M E B M 73 Remedy Planning 243 days Wed 10/1/14 Remedy Planning 85 Final Remedial Design Document 78 days Wed 4/29/15 Final Remedial Design Document 86 Development: Final Remedial Design Report 20 days Wed 4/29/15 Development: Final Remedial Design Report 87 Peer and Technical Review 3 days Wed 5/27/15 Peer and Technical Review 88 Senior Review 3 days Mon 6/1/15 Senior Review 89 PGE Review 5 days Thu 6/4/15 PGE Review 90 Report Revisions 4 days Thu 6/11/15 Report Revisions 91 Submittal: Final Remedial Design Document 1 day Wed 6/17/15 Submittal: Final Remedial Design Document 92 Agency Review 35 days Thu 6/18/15 Agency Review 93 Development: Response to Comments Letter 5 days Thu 8/6/15 Development: Response to Comments Letter 94 PGE Review 2 days Thu 8/13/15 PGE Review 95 Submit RTC Letter to DEQ 0 days Mon 8/17/15 Submit RTC Letter to DEQ 96 DEQ Approval Process 15 days Mon 8/17/15 97 Review of Comment Response 10 days Mon 8/17/15 Review of Comment Response 98 Approval 5 days Mon 8/31/15 Approval 99 Compliance Agreement Signed 0 days Mon 9/7/15 Compliance Agreement Signed 100 Remedy Construction 177 days? Tue 2/24/15 Remedy Construction 101 Pre‐Construction Activities 85 days Tue 2/24/15 Pre‐Construction Activities 102 Pre‐Construction Bathymetric and Topo Survey 1 day Tue 2/24/15 Pre‐Construction Bathymetric and Topo Survey 103 Diver Debris Survey 3 days Tue 3/24/15 Diver Debris Survey 104 Data Processing 30 days Mon 5/4/15 Data Processing 105 Preparation of Final Debris Removal Plan 5 days Mon 6/15/15 Preparation of Final Debris Removal Plan 106 Archaeologist Review 5 days Tue 6/16/15 Archaeologist Review 107 Planning & Mobilization 6 days? Mon 9/7/15 Planning & Mobilization 108 Project Kick‐Off Meeting 1 day? Mon 9/7/15 Project Kick‐Off Meeting 109 Install Monitoring Buoys and Baseline 3 days Mon 9/7/15 Install Monitoring Buoys and Baseline 110 Install Floating Barrier 1 day Mon 9/14/15 Install Floating Barrier 111 Cap Construction 25 days Mon 9/14/15 Cap Construction 112 Debris Removal 5 days Mon 9/14/15 Debris Removal 113 Sand Layer Installation 8 days Mon 9/21/15 Sand Layer Installation 114 Survey and Address Deficiency 5 days Thu 10/1/15 Survey and Address Deficiency 115 Gravel Layer Installation 2 days Thu 10/15/15 Gravel Layer Installation 116 Confirmation Surveys 4 days Mon 10/19/15 Confirmation Surveys 117 Bathymetric and Diver Survey 1 day Mon 10/19/15 Bathymetric and Diver Survey 118 Process Data 3 days Tue 10/20/15 Process Data 119 Contingency Time to Address Cap Deficiencies 3 days Fri 10/23/15 Contingency Time to Address Cap Deficiencies 120 Demobilization 1 day? Wed 10/28/15 Demobilization 121 Post‐Construction Reporting 146 days? Mon 11/2/15 Post‐Construction Reporting 122 Document Preparation 60 days Mon 11/2/15 Document Preparation 123 Peer and Technical Review 5 days Mon 1/18/16 Peer and Technical Review 124 Senior Review 5 days Mon 1/25/16 Senior Review 125 PGE Review 10 days Mon 2/1/16 PGE Review 126 AECOM Incorporate Edits 5 days Mon 2/15/16 AECOM Incorporate Edits 127 Submit to DEQ for Review 45 days Mon 2/22/16 Submit to DEQ for Review 128 Prepare Response to Comments Letter 15 days Mon 4/25/16 Prepare Response to Comments Letter 129 PGE Review 5 days Mon 5/16/16 PGE Review 130 Submit RTC to DEQ 1 day? Mon 5/23/16 Submit RTC to DEQ 131 Post‐Construction Monitoring ‐ 6 Months 42 days Mon 4/11/16 Post‐Construction Monitoring ‐ 6 Months
Page 1 TABLES
Table 1. Infrastructure and Taxlot Summary Portland General Electric Remedial Design Report River Mile 13.5
Date Diameter Constructed/ Field Outfall GPS Outfall GPS Coordinates Structure (inches) Type of Material Installed Owner Drainage Source Status Observation Coordinates (Northing) (Easting) Extends from bank (Feet) RM 13.5 Study Area - Outfall Pipes Stormwater from southern properties ABU956 18 CSP 1998 City Active Active 677974 7647225 Not measured in upland drainage area Stormwater from Tri-County Metropolitan southern properties AQK795 12 DIP 2014 Transportation District of Active Active 678139 7647180 Not measured in upland drainage Oregon area RM 13.5 Study Area - Other Infrastructure NW Natural Gas Company has an Easement, No. 2841, with Gas Pipeline 20 Unk. 1972 NWN -- Active Active -- -- the State of Oregon for the Gas Pipelines. Gas Pipeline 12 Unk. <1972 NWN -- Inactive Inactive ------Water Pipeline 36 Unk. Unk. City -- Active Active ------
Map # Property ID State ID Taxlot Property Owner Address City, State, Zip Tax Rol RM 13.5 Study Area - Taxlots Bordering Study Area
3230 OLD R326759 1S1E03D 500 TL 500 1945 SE WATER AVEOREGON MUSEUM OF SCIENCE & INDUSTRY 1945 SE WATER AVE PORTLAND OR 97214-3356 SECTION 03 1S 1E, TL 500
3230 OLD R247368 1S1E03DD 200 3 TL 200 2201 SE WATER AVEOREGON MUSEUM OF SCIENCE & INDUSTRY 1945 SE WATER AVE PORTLAND OR 97214-3356 PORTLAND GENERAL ELEC STA L, LOT 3 TL 200
TRI-COUNTY METROPOLITAN TRANSPORTATION 3230 R657638 1S1E03DD 202 3 TL 202 SE WATER AVE 4012 SE 17TH AVE PORTLAND OR 97202-3940 PORTLAND GENERAL ELEC STA L, LOT 3 TL 202 DISTRICT OF OREGON
3230 R657639 1S1E03DD 203 3 TL 203 SE CARUTHERS STOREGON MUSEUM OF SCIENCE & INDUSTRY 1945 SE WATER AVE PORTLAND OR 97214-3356 PORTLAND GENERAL ELEC STA L, LOT 3 TL 203
3230 Old R27577 1S1E03DD 700 30 TL 700 100 SE CARUTHERS STAMERICAN WATERWAYS, INC. 110 SE CARUTHERS ST PORTLAND OR 97214-4513 STEPHENS ADD, BLOCK 30 TL 700, DEPT OF REVENUE
Notes: City = City of Portland CSP = concrete sewer pipe NWN = Northwest Natural DIP = ductile iron pipe Unk. = Unknown
AECOM Page 1 of 1 \\1571sr-p8pwcs1\projects\25697878 PGE Cont Env Svcs 2013\5000 Technical\RM 13.1_13.5 FS\RM 13.5 RD\Revised-Final-RD\Tables\Tables_combined Table 2. Remedial Action Objectives and Goals Portland General Electric Remedial Design Report River Mile 13.5
RAO Remediation Action Objective Remedial Goal Number 1 Prevent unacceptable exposures of the COCs in Isolate the risk driver COCs in surface sediment to the maximum extent practicable, surface sediment to human health and ecological specifically targeting the areas where discrete concentrations of COCs are elevated and co- receptors and treat areas identified as sediment located; reduce the surface weighted area concentration (SWACs) for risk driver COCs within remediation areas. Reducing concentration, the remediation area to the CLs (represented by the mean upriver background volume, and/or mobility of the COCs to reduce the concentrations, consistent with the Portland Harbor Draft Feasibility Study dated March 30, risk in RM 13.5 surface sediment. 2012, or most recent level consistent with the Portland Harbor). See Table 3 for site-specific cleanup levels for the risk driver COCs. 2 Reduce migration of the COCs in the sediment to Follow best management practices during construction to minimize suspension of bedded the water column or to other areas of the river. sediment and maintain water quality within all permitted levels throughout construction. Maintain a minimum cap thickness after placement to achieve long-term protection, consistent with the Final Remedial Design Report River Mile 13.5, Willamette River, Portland, Oregon. Prepared for Portland General Electric Company by AECOM, July 2015.
3 Support green remediation initiatives and best Standard procedures and goals for green remediation will be established during the final management practices to the maximum extent remedy design, with input from the in-water construction contractor, once selected. practicable. Strategies will focus on minimizing emissions, reducing energy consumption and minimizing volume and toxicity of waste generation to support green remediation strategies and best management practices.
4 Protect worker health and safety and minimize short- During implementation, OSHA HAZWOPER requirements are used to define chemical- term risks during implementation of the remedy. specific concentrations for worker exposure. Additional protection of worker health and safety are also to be specified in a remedy-specific HASP.
Notes: CL = Cleanup Levels COCs = constituents of concern HASP = Health and Safety Plan RAO = Remedial Action Objective RM = river mile SWACs = surface weighted area concentrations OSHA = Occupational Safety and Health Administration HAZWOPER = Hazardous Waste Operations and Emergency Response
AECOM Page 1 of 1 \\1571sr‐p8pwcs1\projects\25697878 PGE Cont Env Svcs 2013\5000 Technical\RM 13.1_13.5 FS\RM 13.5 RD\Revised‐Final‐RD\Tables\Tables_combined Table 3. Cleanup Levels Portland General Electric Remedial Design Report River Mile 13.5
Point-Based SWAC Based Risk Driver COC Cleanup Level1 Cleanup Level2
PCB Aroclors (ug/kg dw) Total PCBs 17 5.40 Dioxins/Furans (ng/kg dw) Total Dioxin/Furan TEQ - Mammals 2.16 0.72 Pesticides (ug/kg dw) Total DDx 3.03 1.43
Notes: 1) The CLs shown are the UPL of background data upstream of the Portland Harbor superfund site. Values are those using EPA’s approach for outliers taken from Appendix A of the draft Feasibility Study, March 2012. UPL values are suitable for comparison with data from individual (discrete) sample locations. 2) The CLs are the EPA cases for the mean MUBCs for the lower Willamette River taken from Appendix A of the draft Feasiblity Study, March 2012. MUBCs are suitable for comparison with data from SWACs. These values were used as point-based action levels to develop the target area for the RM 13.5 remedial action. ug/kg = micrograms per kilogram ng/kg = nanograms per kilogram CL = Cleanup Levels DDx = sum of DDD, DDE, and DDT DDD = dichlorodiphenyldichloroethane DDE = dichlorodiphenyldichloroethylene DDT = dichlorodiphenyltrichloroethane dw = dry weight EPA = Environmental Protection Agency MUBC = mean upriver background concentration PCB = polychlorinated biphenyl SWAC = surface weighted area concentration TEQ = total equivalency factor UPL = upper prediction limit
AECOM \\1571sr-p8pwcs1\projects\25697878 PGE Cont Env Svcs 2013\5000 Technical\RM 13.1_13.5 FS\RM 13.5 RD\Revised-Final- Page 1 of 1 RD\Tables\Tables_combined Table 4. Surface Sediment Results Portland General Electric Remedial Design Report RM 13.5
# of Surface1 Minimum Maximum # of 90-Percent Median Risk Driver COC Units Sediment # of Detects Reported Reported Location Exceedances UCL Concentration2 Samples Concentration Concentration
Total PCBs as Aroclors ug/kg dw 16 15 11 66.3 2.10 U T 37.3 134 T DPSC-G041
Total Dioxin/Furan TEQ - mammals ng/kg dw 8 8 5 9.35 0.475 J T 3.66 20.0 J T IPC-S022
Total DDx ug/kg dw 16 13 9 6.48 0.150 J T 3.68 14.9 J T IPC-C019
Notes: 1) Surface sediment represents the mixing zone sediment and extends from the sediment surface to 1 foot below the sediment surface. 2) The mean for data sets with an even number of sediment samples is defined to be the mean of the two middle values; therefore no qualifiers are assigned to the resulting value. bold = analyte above the SWAC-Based cleanup level (See Table 3 for determination of cleanup levels.) ug/kg dw = micrograms per kilogram, dry weight mg/kg dw = milligrams per kilogram, dry weight ng/kg dw= nanograms per kilogram, dry weight COC = constituent of concern DDx = sum of DDD, DDE, and DDT DDD = dichlorodiphenyldichloroethane DDE = dichlorodiphenyldichloroethylene DDT = dichlorodiphenyltrichloroethane J = estimated concentration PCB = polychlorinated biphenyl U = not detected above the laboratory method detection limit shown UCL = upper confidence limit T = total, sum of individual constituents SWAC = surface weighted area concentrations TEQ = total equivalency factor (TEQ)
AECOM Page 1 of 1 \\1571sr‐p8pwcs1\projects\25697878 PGE Cont Env Svcs 2013\5000 Technical\RM 13.1_13.5 FS\RM 13.5 RD\Revised‐Final‐RD\Tables\Tables_combined Table 5. Subsurface Sediment Results Portland General Electric Remedial Design Report River Mile 13.5
# of Subsurface Location and # of 90-Percent Minimum Maximum Risk Driver COC Units Sediment # of Detects Depth Below Exceedances UCL Reported Median Reported 1 Mudline Samples Concentration Concentration2 Concentration DPSC-C022 Total PCBs as Aroclors ug/kg dw 17 14 10 208 2.1 U T 37.3 J T 610 T 3.15-5.12 ft Total Dioxin/Furan TEQ - IPC-S022 ng/kg dw 12 12 6 11.0 0.0593 J T 2.10 19.3 J T mammals 1.0-2.5 ft DPSC-C022 Total DDx ug/kg dw 17 13 8 24.5 0.064 J T 3.01 J T 70.6 J T 3.15-5.12 ft
Notes: 1) Subsurface sediment represents sediment at depths greater than 1 foot below the sediment surface. 2) The mean for data sets with an even number of sediment samples is defined to be the mean of the two middle values, therefore no qualifiers are assigned to the resulting value. bold = analyte above the SWAC-Based cleanup level (See Table 3 for determination of cleanup levels.) ug/kg dw = micrograms per kilogram, dry weight mg/kg dw = milligrams per kilogram, dry weight ng/kg dw= nanograms per kilogram, dry weight COC = constituent of concern DDx = sum of DDD, DDE, and DDT DDD = dichlorodiphenyldichloroethane DDE = dichlorodiphenyldichloroethylene DDT = dichlorodiphenyltrichloroethane ft = feet J = estimated concentration PCB = polychlorinated biphenyl U = not detected above the laboratory method detection limit shown UCL = upper confidence limit SWAC = surface weighted area concentrations T = total, sum of individual constituents TEQ = total equivalency factor (TEQ)
AECOM Page 1 of 1 \\1571sr‐p8pwcs1\projects\25697878 PGE Cont Env Svcs 2013\5000 Technical\RM 13.1_13.5 FS\RM 13.5 RD\Revised‐Final‐RD\Tables\Tables_combined Table 6. Summary of Grain Size Data Portland General Electric Remedial Design Report River Mile 13.5
Sample Grain Size Distribution (in percent) Depth Sample Location Sample ID Interval Gravel Sand Silt and Clay 2µm1 (ft bss) IPC-S020 IPC-S020-SS 0.0-1.0 3 43 46 6 RM13.5-G5 RM13.5-G5-SS-03 0.0-1.5 4.5 44.5 51 6 RM13.5-G6 (Dup) RM13.5-G6-SS-02 0.0-1.0 0 21 79 7 RM13.5-G6 RM13.5-G6-SS-03 0.0-1.0 0 40 60 9 RM13.5-G6 RM13.5-G6-AA-03 1.0-3.0 0 30 70 12 RM13.5-G6 RM13.5-G6-CC-03 2.5-4.5 0 30 70 12 RM13.5-G8 RM13.5-G8-AA-03 2.5-4.5 9 33 58 10
Notes: 1) Fraction represents the silt and clay fraction less than 2µm (clay fraction) ft = feet bss = below sediment surface RM = river mile SS = Surface Sample (assumes surface sediment extends to 1 foot below the sediment surface) AA and CC = subsurface sample µm = micron
AECOM Page 1 of 1 \\1571sr-p8pwcs1\projects\25697878 PGE Cont Env Svcs 2013\5000 Technical\RM 13.1_13.5 FS\RM 13.5 RD\Revised-Final-RD\Tables\Tables_combined Table 7. SWAC Values Portland General Electric Remedial Design Report River Mile 13.5
Total SWAC Area of Surface Total PCBs as Dioxin/Furan Total DDx Evaluation Sediment1 Aroclors TEQ-Mammals (µg/kg) ID (SF/Acres) (µg/kg) (ng/kg)
Baseline SWAC for RM 13.52 94,852 / 2.18 50.6 3.22 4.89
Estimated Post-Remedy SWAC for RM 13.53 37,967 / 0.87 5.47 0.86 1.16
MUBC 5.40 0.72 1.43 and SWAC-Based Cleanup Levels4
Notes: 1) Area of the surface sediment is based on overall study area footprint (94,852 square feet) and assumes surface sediment extends to 1 foot below the sediment surface. 2) The baseline SWAC values are calculated from the sum of a series of products of normalized Thiessen polygon areas and associated (by sampling location) sediment concentrations. The SWACs reflect Portland Harbor Risk Assessment rules, including non-detected analyte group totals at the highest MDL. 3) The estimated Post-Remedy SWAC values are calculated from the sum of a series of products of normalized Thiessen polygon areas and associated sediment concentrations for those polygons that have been capped (using bed replacement value of natural background) and those polygon areas remaining oustide of the target cap area (no capping, use baseline concentrations). The SWACs reflect Portland Harbor Risk Assessment rules, including non-detected analyte group totals at the highest MDL. 4) Background concentrations for contaminants in sediment (in dry weight) from the Portland Harbor, Draft Feasibility Study, March 30, 2012.
DDx = sum of dichlorodiphenyldichloroethane, dichlorodiphenyldichloroethylene, and dichlorodiphenyltrichloroethane ID = identification µg/kg = micrograms per kilogram mg/kg = milligrams per kilogram MDL = method detection limit MUBC = mean upriver background concentration NA = not applicable; all baseline concentrations are below the initial screening criteria shown in Table 12. NC = not calculated ng/kg = nanograms per kilogram MUBC = mean upriver background concentration PCB = Polychlorinated biphenyl RM = river mile SF = square feet SWAC = surface weighted area concentration TEQ = toxic equivalency factor
AECOM Page 1 of 1 \\1571sr-p8pwcs1\projects\25697878 PGE Cont Env Svcs 2013\5000 Technical\RM 13.1_13.5 FS\RM 13.5 RD\Revised-Final-RD\Tables\Tables_combined Table 8. Permissible Shear and Velocity for Selected Capping Materials Portland General Electric Remedial Design Report River Mile 13.5
Permissible Shear Stress Permissible Velocity Capping Material1 Material Type (lbs/sq ft) (ft/sec)
Soil Fine colloidal sand 0.02 - 0.03 1.5 Sandy loam (noncolloidal) 0.03 - 0.04 1.75 Alluvial silt (noncolloidal) 0.045 - 0.05 2 Silty loam (noncolloidal) 0.045 - 0.05 1.75 – 2.25 Alluvial silt (colloidal) 0.26 3.75 Graded silts to cobbles 0.43 4 Gravel/Cobble 1-in 0.33 2.5 – 5 2-in 0.67 3 – 6 6-in 2 4 – 7.5 12-in 4 5.5 – 12
Rip-Rap 6 – in d50 2.5 5 – 10
12 – in d50 5.1 10 – 13 Maximum Near-Shore Maximum Predicted River- River Velocity Predicted Item Description2 Modelling Software Bottom Shear Stress for 100 Year Flood Event (lbs/sq ft) (ft/sec) Results of Fluvial Analysis and Hydrodynamic Modeling for HEC-RAS and Mike 213 0.18 5 Study Areas
Notes: 1) Literature values for capping material are an excerpted from Stability Thresholds for Stream Restoration Materials by Craig Fischenich, USAE Research and Development Center. ERDC TN-EMRRP-SR-29. May 2001. 2) URS, 2014. Final Feasibility Study for River Miles 13.1 and 13.5, Willamette River, Portland, Oregon. Prepared for Portland General Electric Company by URS. November 2014. 3) U.S. Army Corps of Engineers HEC-RAS model was used to conduct the far-field, one-dimensional hydraulic analysis of the Willamette River. MIKE 21, a two-dimensional, free-surface flow modeling system, was used to calculate the near-field, flow velocity and bed shear stresses at RM 13.5. bold = approximate range of selected surface material for cap lbs/sq ft = pounds per square foot ft/sec = feet per second in = inches
d50 = median value of the grain size distribution
AECOM Page 1 of 1 \\1571sr-p8pwcs1\projects\25697878 PGE Cont Env Svcs 2013\5000 Technical\RM 13.1_13.5 FS\RM 13.5 RD\Revised-Final-RD\Tables\Tables_combined Table 9. Summary of Monitoring Requirements Portland General Electric Remedial Design Report River Mile 13.5
Pre-Construction Reporting Description of Monitoring Item Frequency Review Requirements Document Reference Monitoring Requirements Requirements 2 days Baseline Sound Monitoring Baseline sound measurements to establish background within the work area, measured at adjacent riverbank. DFR Review for approval by CFM CQAP Section 4.1.1 1 measurements at 8 am, 12 noon, and 4 pm 2 days Baseline Air Monitoring Baseline dust monitoring to establish background within the work area. DFR Review for approval by CFM CQAP Section 4.1.1 1 measurements at 8 am, 12 noon, and 4 pm Baseline Turbidity Monitoring at Upgradient and Downgradient Monitoring Two, 10-hour days Baseline turbidity to establish background values and tidal influence on turbidity in RM 13.5. DFR Review for approval by CFM CQAP Section 4.1.4 Stations 1 measurement every hour Trigger the water quality monitoring stations to verify the locations represent the conditions upgradient of the work area and also Review for approval by CPC Water Quality Monitoring Station Calibration/Position Evaluation One test at each monitoring station Submittal Register CQAP Sections 4.1.3 and 4.2.2.3 downgradient of the work area. NMFS Laboratory testing to verify the fill material meets the screening level for the constituents of concern and physical properties for size and One, 5-point composite samples per 5,000 cubic yards for each Coarse Sand Fill Verification Submittal Register Review for approval by PE CQAP Section 4.2.1 organic content. borrow source Pre-Construction multibeam bathymetric survey to evaluate river bed baseline conditions and establish baseline for all project volume Pre-Construction Bathymetric Survey Once Submittal Register Review for approval by PE CQAP Sections 4.2.2.1 and 4.2.2.3 estimates. During Construction Reporting Description of Monitoring Item Frequency Review Requirements Reference Monitoring Requirements Requirements One, 2-point composite sample for every 2 drums of waste Debris and Liquid Waste Profiling Laboratory testing of debris to determine waste disposition. Two, 2-point composite samples for every 5 roll-offs Submittal Register Review for approval by CFM CQAP Section 4.2.2.2 1 grab sample for every 1,000 gallons of wastewater Sound measurements to establish compliance with 70 decibel sound limit during daylight hours in commercial zone, measured at adjacent Sound Monitoring 1 measurements weekly during active construction DFR Review for approval by CFM CQAP Section 4.1.1 riverbank. Dust measurements to establish compliance with levels exceed 3 mg/m3 respirable particles in the vicinity of the workers or 10 mg/m3 1 measurements weekly during active construction, or as needed if Air Monitoring DFR Review for approval by CFM CQAP Section 4.1.1 inhalable particles at the project work limits of RM 13.5. dust is visible in work area. Routine measurements to establish upgradient turbidity. Must record, date, time, weather, station location, and Morrison Bridge River Daily Turbidity Monitoring at Upgradient Monitoring Station DFR Review for approval by CFM CQAP Section 4.1.4 gauge reading. Measurements per Permit Requirements Review for approval by CFM Routine measurement for compliance permit with the water quality permit. Daily Turbidity Monitoring at Downgradient Monitoring Station Must record date, time, weather, station location. DFR CQAP Section 4.1.4 Measurements per Permit Requirements Notification to DEQ and NMFS Compliant if measurement at downgradient station is not greater than 10 percent higher than upgradient station. required if out of compliance Turbidity meter calibration Calibrate in accordance with the manufacturer's specifications. Weekly DFR Review for approval by CFM CQAP Section 4.2.2.3
Daily Bathymetric Surveys Single beam bathymetric survey to evaluate material placement thickness, placement areas, and verify slopes. Daily during fill placement DFR Review for approval by CFM CQAP Section 4.2.2.3
Diver Survey Diver surveys to inspect placement of the cap materials. As needed DFR Review for approval by CFM CQAP Section 4.2.2.3 Sediment core collection following placement of first 12-inch lift of coarse sand fill to log, inspect, and evaluate mixing between fill and First Lift Sediment Cores 4 sediment cores Submittal Register Review for approval by PE CQAP Section 4.2.2.3 bedded sediment. Sediment core collection following placement of second 12-inch lift of coarse sand fill to log, inspect, and evaluate mixing between fill and Second Lift Sediment Cores 2 sediment cores Submittal Register Review for approval by PE CQAP Section 4.2.2.3 bedded sediment, prior to placement of armor layer. Following installation of the coarse sand isolation layer, a multibeam bathymetric survey to provide a comprehensive survey of the Isolation Layer Bathymetric Survey Once Submittal Register Review for approval by PE CQAP Sections 4.2.2.1 and 4.2.2.3 elevation and determine final volume for sand placed, prior to placement of armor layer. Post-Construction/Pre-Demobilization Reporting Description of Monitoring Item Frequency Review Requirements Reference Monitoring Requirements Requirements Sediment core collection following placement of second 12-inch lift of coarse sand fill to inspect and evaluate mixing between fill and Confirmation Sediment Core 1 sediment core Submittal Register Review for approval by PE CQAP Section 4.2.2.3 bedded sediment, or if needed as follow-up after placement of third lift to address low spots. Following cap installation (isolation layer and armor layer), a multibeam bathymetric survey to establish cap elevation and determine final Final Bathymetric Survey Once Submittal Register Review for approval by PE CQAP Sections 4.2.2.1 and 4.2.2.3 volume estimates. Final Diver Survey Diver survey to inspect placement of the materials. Once DFR Review for approval by CFM CQAP Sections 4.2.2.1 and 4.2.2.3 Post-Construction Reporting Description of Monitoring Item Frequency Review Requirements Reference Monitoring Requirements Requirements
Post-Construction Bathymetric Survey Post-construction multibeam bathymetric survey after 6 months to establish cap elevation and determine final volume estimates. Once, 6 months following cap installation Tech Memo to DEQ Review for approval by PE and DEQ CQAP Sections 4.2.2.1 and 4.2.2.3
Post-Construction Diver Survey Diver survey to inspect cap, following period of high-water within the river. Once, 6 months following cap installation Tech Memo to DEQ Review for approval by PE and DEQ CQAP Sections 4.2.2.1 and 4.2.2.3
Notes: CFM = Consultant Field Manager CPC = Consultant Permit Coordinator CQAP = Construction Quality Assurance Plan, River Mile 13.5. Prepared by AECOM, July 2015 for Portland General Electric. DEQ = Department of Environmental Quality DFR = Daily Field Report mg/m3 = milligrams per cubic meter NMFS = National Marine Fisheries Service PE = Professional Engineer RM = River Mile
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