AECOM-Revised Final Remedial Design Rport RM 13 5(No

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

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