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March 25, 2004
King County working with cities, agencies to protect Des Moines Creek watershed
King County Executive Ron Sims today announced plans to begin working with the county's partners on construction projects that will improve drainage, reduce erosion and improve salmon habitat in the Des Moines Creek watershed.
Sims is proposing an interlocal agreement with the City of SeaTac, the City of Des Moines, the Port of Seattle, and the Washington State Department of Transportation to construct, operate and maintain a series of capital projects that will implement the Des Moines Creek Basin Plan.
"These capital projects represent a major accomplishment for the Des Moines Creek Basin Committee and for each of the individual jurisdictions involved," Sims said. "Working collectively, the participating agencies have developed a robust watershed management plan that will protect natural resources much more effectively than existing regulations while providing significant cost savings to the public. Providing regional leadership and technical expertise to the effort, King County has played a key role in the development of this unique set of projects. Completion of these projects will not only be a major step toward restoration of Des Moines Creek, but will provide a template for future watershed restoration efforts."
The projects, on which construction is slated to begin this year, include:
- A regional detention facility (RDF) to provide stormwater storage and reduce peak flows and channel erosion.
- A bypass pipe to reduce peak flows and optimize storage volume in the RDF.
- A flow augmentation facility to maintain minimum stream flows during dry periods to ensure fish survival.
- Habitat enhancement and restoration to improve fish passage, enhance habitat and stabilize eroding stream bed and banks.
- Marine View Drive culvert replacement to eliminate a significant fish passage barrier and open up more than two more miles of habitat.
The project design phase is near completion and the new interlocal agreement proposed by Sims to the King County Council would provide for construction of the projects, project monitoring post-construction and ongoing operation and maintenance.
Des Moines Creek drains a highly urbanized Basin within the cities of Des Moines and SeaTac. The Basin includes a large part of SeaTac International Airport as well as extensive commercial and high-density residential development. Because much of the Basin was developed prior to the implementation of effective stormwater detention requirements, the stream experiences erosive flows in the winter and chronically low flows in the summer. The flows have degraded Des Moines Creek by increasing channel erosion and downcutting, washing away salmon spawning gravel and large woody debris, and decreasing the number and quality of pools available for habitat within the stream.
Fish access to the stream is also limited to the lower 0.4 miles because of an undersized culvert located under Marine View Drive at approximately 216th Street in Des Moines. Increased flooding, erosion within the ravine, and the potential for catastrophic failure of the culvert under Marine View Drive also put public facilities at risk. Despite these problems, the majority of the lower 2 miles of the 3.5-mile stream is in public ownership and has a well-vegetated riparian buffer and the potential to support a viable population of salmon and trout.
The total construction cost for the projects is approximately $18 million. It is estimated that King County will incur costs of approximately $1.5 million in fulfilling its functions as the party responsible for constructing the flow augmentation project and habitat restoration project, and approximately $500,000 to perform the Oversight and Compliance Coordinator function. The county will be fully reimbursed by the other parties for these costs, as well as an additional $279,000 for costs previously incurred to complete design, environmental documentation, and permitting work.
In the early 1990s, SeaTac, Des Moines, the Port of Seattle and King County, which at the time had jurisdiction in a small portion of land area in the Basin, initiated discussions on resolving current and potential future surface water-related issues. The jurisdictions, working as the Des Moines Creek Basin Committee, agreed that cooperatively developing a watershed-wide basin plan was the most efficient and effective way to address the issues, and in 1996 entered into an interlocal agreement to fund and develop the Des Moines Creek Basin Plan. Completed in 1997, the Plan assessed water resource conditions including aquatic habitat and evaluated surface water-related problems including flooding, erosion, sedimentation, and water quality impairment.
In 1999, the Washington State Department of Transportation joined the Basin Committee, and will match the substantial construction funding already committed to by the Port of Seattle. Although the small area of King County jurisdiction in the Basin had been annexed, the Basin Committee expressed the strong desire for King County to remain a project partner into future phases because of the county's regional expertise in watershed planning, stormwater management and habitat restoration.
For more information about the Des Moines Creek Basin Plan, contact Glenn Evans, at 206-296-8386.
Updated: March 25, 2004
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