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Dairy Creek Feasibility Study ATR Report/Pre-Decisional: Do Not Distribute U.S. Army Corps of Engineers, Portland District (Contract No.W9127N-11-D-0011) Feasibility Study and Task Order No. 0029 Environmental Assessment Report Dairy Creek Restoration Feasibility Study Sauvie Island, OR Prepared by: HDR Engineering, Inc. 1001 SW 5th Ave., Suite 1800 Portland, OR 97204-1134 July 2013 ATR Report/Pre-Decisional: Do Not Distribute This page left intentionally blank ATR Report/Pre-Decisional: Do Not Distribute EXECUTIVE SUMMARY Under Section 1135 of the Water Resources Development Act (WRDA), the U.S. Army Corps of Engineers (USACE) has conducted a feasibility study for the Dairy Creek Restoration Project (Project). The West Multnomah Soil and Water Conservation District (WMSWCD) is the local sponsor. The 10,580-acre study area includes Sturgeon Lake and the surrounding lands on Sauvie Island, west of Portland, Oregon. Sturgeon Lake and related hydrologic features including Dairy Creek provide important habitats for resident and migratory fish and wildlife species. Situated at the confluence of the Columbia and Willamette Rivers, the Project area is a foraging, rearing, and refuge resource for endangered salmonids. The Lake provides wintering habitat for approximately 150,000 ducks, geese, and swans annually and is a key stop on the Pacific flyway. Over the past 60 years, hydrologic modifications to the Lake and surrounding waters have resulted in a decrease in Lake size and a disconnection of Dairy Creek. The goal of the Project is to restore long-term function of Sturgeon Lake and increase aquatic areas and habitat value for fish and wildlife. The Project is needed to remedy the degradation of these habitats as a result of hydrologic manipulation from Federal levees and Columbia River Power System Operations. Within the framework and constraints of the Section 1135 objectives, the following objectives were established: § To reestablish rearing juvenile salmonid (coho and Chinook) ingress and egress opportunities to Sturgeon Lake from Columbia River; § To maintain open water areas that support a diversity of wintering waterfowl to the extent practicable; § To restore off-channel habitat quality and quantity for rearing juvenile salmonids and flood refugia for juveniles and adults; § To reconnect and restore more natural hydrologic inputs between Sturgeon Lake and surrounding water bodies; and § To reconstruct Dairy Creek channel to improve habitat and riparian function, where feasible. This Feasibility Study Report examines existing conditions at Dairy Creek and Sturgeon Lake and proposes alternatives for restoring important habitat functions. Based on the results of the cost benefit evaluation, the USACE identified Dairy Creek (Alternative 3) as the recommended plan to meet Project goals and objectives. The proposed plan is to restore the current Dairy Creek channel between Sturgeon Lake and the Columbia River to increase hydrologic connection, increase circulation in Sturgeon Lake, and provide direct fish access from the Columbia River. The results of these actions will serve to improve Lake habitat function and quantity for fish and waterfowl. The total Federal cost, including costs for operation and maintenance (O&M), and monitoring, but excluding feasibility study costs, is estimated at $7,506,000. The total annualized O&M cost is estimated at $32,000. WMSWCD is expected to pay for 25 percent of the Total Project Cost ($1,660,000). Feasibility Study and Environmental Assessment Report Page ES-1 Dairy Creek Restoration Feasibility Study July 2013 ATR Report/Pre-Decisional: Do Not Distribute This page left intentionally blank Feasibility Study and Environmental Assessment Report Page ES-2 Dairy Creek Restoration Feasibility Study July 2013 ATR Report/Pre-Decisional: Do Not Distribute TABLE OF CONTENTS EXECUTIVE SUMMARY ACRONYMS AND ABBREVIATIONS 1.0 INTRODUCTION ................................................................................................. 1 1.1 Study Authority ............................................................................................................... 1 1.2 Background .................................................................................................................... 3 1.3 Purpose and Need .......................................................................................................... 4 1.4 Study Area Description ................................................................................................... 4 1.5 Relationship to Regional Studies .................................................................................... 7 1.5.1 ODFW 2010 SIWA Management Plan ................................................................................................... 7 1.5.2 The Lower Columbia River Conservation and Recovery Plan for Oregon Populations of Salmon and Steelhead ................................................................................................................................................ 8 1.5.3 Federal Columbia River Power System Biological Opinions .................................................................. 8 1.6 Expected Success of the Project .................................................................................... 9 2.0 EXISTING AND FUTURE WITHOUT-PROJECT CONDITION .......................... 11 2.1 Existing Conditions ........................................................................................................11 2.1.1 Water Resources .................................................................................................................................. 11 2.1.2 Surface Water Hydrology ...................................................................................................................... 14 2.1.3 Lake Sediment Dynamics ..................................................................................................................... 18 2.1.4 Water Management and Uses .............................................................................................................. 22 2.1.5 Water Quality ........................................................................................................................................ 24 2.1.6 Geology and Soils ................................................................................................................................. 27 2.1.7 Wetlands ............................................................................................................................................... 29 2.1.8 Fish and Aquatic Resources ................................................................................................................. 33 2.1.9 Wildlife .................................................................................................................................................. 34 2.1.10 Vegetation ............................................................................................................................................. 36 Feasibility Study and Environmental Assessment Report Page i Dairy Creek Restoration Feasibility Study July 2013 ATR Report/Pre-Decisional: Do Not Distribute 2.1.11 Special Status Species ......................................................................................................................... 37 2.1.12 Historical and Cultural Resources ........................................................................................................ 43 2.1.13 Socio-economic, Land Use, and Recreation ........................................................................................ 44 2.1.14 Air Quality and Noise ............................................................................................................................ 47 2.2 Future Without-Project Condition (No Action Alternative) and Cumulative Effects ........48 2.2.1 Water Resources .................................................................................................................................. 48 2.2.2 Lake Sediment Dynamics ..................................................................................................................... 48 2.2.3 Water Management and Uses .............................................................................................................. 51 2.2.4 Water Quality ........................................................................................................................................ 51 2.2.5 Geology and Soils ................................................................................................................................. 51 2.2.6 Wetlands ............................................................................................................................................... 51 2.2.7 Fish and Aquatic Resources and Wildlife ............................................................................................. 51 2.2.8 Vegetation ............................................................................................................................................. 52 2.2.9 Special Status Species ......................................................................................................................... 52 2.2.10 Historic and Cultural Resources ........................................................................................................... 53 2.2.11 Socio-economic, Land Use, and Recreation .......................................................................................
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