DESCRIPTION
This fish passage and estuary restoration culvert replacement project is addressing a partial barrier to fish migration due to the culvert being undersized and restoring connectivity to a vital Puget Sound estuary. The goals of the project are to improve habitat conditions and accessibility for salmon and cutthroat trout spawning and rearing use. The current tidal culvert is only passable during high tides and cuts off natural estuary processes such as sediment transport and natural hydraulic flow regimes impacting several salmonoid species. Schoolhouse Creek is the largest creek on Anderson Island in Water Resource Inventory Area 15. The road, Eckenstam Johnson, is built over imported fill that cuts off the estuary from Oro Bay. The project site is at the mouth of Schoolhouse Creek and Oro Bay directly north of the Nisqually River and part of the Nisqually Reach Aquatic Reserve. The proposed project will replace the existing 4-foot round culvert with either a 50' span arch culvert or a 90' bridge span. The project will return this roadway crossing to a more natural condition similar to its unaltered natural condition while providing a safe roadway for the traveling public. We have selected a concrete structure rather than steel that can withstand being submerged for short periods of time during tidal events throughout the lifetime of the structure.
Schoolhouse Creek at the Mouth will address the last remaining partial barrier to fish migration due to the current culvert being undersized, while restoring connectivity to a vital Puget Sound estuary. This project aims to improve fish passage at a known fish passage barrier culvert, restore natural processes in the estuary and reconnect the estuary to the mainstem of Schoolhouse Creek. The current tidal culvert is only passable during high tides and cuts off natural estuary processes such as sediment transport and natural hydraulic flow regimes impacting several salmonoid species. The proposed project will replace the existing 60-inch round concrete culvert with a 62-foot bridge span with 44-foot opening to address fish passage issues. The project will return this roadway crossing to a more natural condition, similar to its unaltered natural condition, while providing a safe roadway for the traveling public. The tidal culvert replacement will benefit the natal coho, chum and cutthroat population that use Schoolhouse Creek for spawning and rearing. Additional benefits will be in support of Chinook stocks from the Nisqually, Puyallup, Duwamish, and Snohomish basins, as identified in the Priority Chinook Stocks Report. Juvenile hatchery Chinook sampling in these locations have tracked hatchery origins to these systems. In the 2018 report, additional hatchery Chinook stocks not identified as priority stocks were found in the area through sampling, including the Chambers Creek,
