Walker and Sequoia Creek Culverts Replacement Project

Project Summary

The Walker and Sequoia Creeks realignment projects consists of three phases: design, property acquisition, and construction.  In 2020, consultant Gray & Osborne, Inc. prepared a technical memo after evaluating whether two existing culverts had the capacity to convey peak stormwater flow.  The culverts have been identified as partial fish barriers that are undersized to convey flows from Walker Creek and its tributary, Sequoia Creek. The existing culverts will be removed and replaced with a bridge at 12^th Avenue SW (over lower Walker and Sequoia Creeks) and a box culvert at SW 174^th Street (to convey upper Sequoia Creek) that will be designed to provide fish passage.

Washington Department of Fish and Wildlife (WDFW) has identified the following species in Walker and Sequoia Creeks that are listed as Threatened under the Endangered Species Act (ESA): Puget Sound chinook salmon and steelhead. Additionally, the Creeks are habitat for the following species that have been identified as Priority Species by WDFW: resident coastal cutthroat, fall chum salmon, and coho salmon.

12^th Avenue SW – The Project will remove three under-sized culverts that convey Walker and Sequoia creeks across 12^th Avenue SW, and replace them with a bridge. The existing culverts impede fish passage and cause flooding of the roadway and adjacent properties during storm events every several years. The proposed bridge will improve access to 415 meters of Walker Creek and 235 meters of Sequoia Creek for anadromous salmonids. Property acquisition has been funded through a combination of a grant through the King County Conservation Futures and local funding. That property acquisition will be complete in 2023. Demolition of existing structures on the site has been funded by a Cooperative Watershed grant from the King County Flood Control District. Construction of the proposed bridge is planned for 2024.

SW 174^th Street – The Project will remove an under-sized culvert that conveys Sequoia Creek across 174^th Avenue SW. The existing culvert is subject to frequent plugging with debris, which further impedes fish passage and access to 300 meters of anadromous salmonid habitat. Construction of the proposed box culvert is planned for 2025.

If you have any questions, please feel free to contact Public Works Director Ken Courter (206) 248-8269 or Stormwater Coordinator Jessie Medrow (206) 248-8256.

Phase 1 – Design (Complete)

Project Update

• • August 2022 –The City of Normandy Park has completed the design for the replacement of undersized culverts at two locations:
    • 12^th Avenue SW – A bridge that will replace two existing 18-inch culverts that convey Sequoia Creek and one 24-inch culvert that conveys Walker Creek in the vicinity of 12^th Avenue SW and SW Eastbrook Road. Sequoia Creek will be realigned to allow it to discharge directly to Walker Creek.
    • SW 174^th Street – A new box culvert will replace an existing 24-inch culvert that conveys Sequoia Creek across SW 174^th

Project Timeline & Funding Sources

• • 2020 King County Flood Control District: Flood Reduction Grant (60% Design) – $300,000
  • 2021 King County Flood Control District: Flood Reduction Grant (90% Design) – $200,000
  • 2022 King County Flood Control District: Flood Reduction Grant (100% Design to be completed in 2023) – $150,000

Phase 2 – Property Acquisition (Complete)

Project Update

• • December 13, 2022 – Purchase and Sale Agreement Signed
    Council approved the PSA for the property acquisition of 17622 12th Ave SW at the December council meeting.

Project Timeline & Funding Sources

• • 2021 King County Conservation Futures Grant received – $600,000
  • 2019 – 2022 King County Parks Levy Funds – $521,543
  • REET Funds – $212,757

Phase 3 – Demolition (2024) & Construction (2025)

Project Update

• • February 6, 2023 – Federal grant application submittal due
    The city intends to apply for Removal, Replacement, and Restoration Grant Program (Culvert AOP Program)

Project Timeline & Funding Sources

• • 2022 Cooperative Watershed Management Grant awarded to Normandy Park for demolition of structures – $150,000
  • 2023 – Estimated start date of demolition and site prep
  • 2024 – Estimated start date of construction at the 12th Ave SW location, pending grant funding
  • 2025 – Estimated start date of construction at the SW 174th Street location, pending grant funding
  • 2026 – Once the culverts are replaced, property is to be converted to open space park with trails and interpretive signs for the public to enjoy.