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