DESCRIPTION
The restoration project is located at River Mile 2 of the Duwamish Waterway at the site of the former Seaboard Lumber Mill which operated from around 1929 until the early 1980's. The site is in the vicinity of Kellogg Island and on the last remaining oxbow of the Duwamish River system. The site contains 5.7 acres of upland and 10 acres of tidelands. Historically, the upland site was a marsh/channel of the Duwamish River. Developed as an industrial site, the area was filled with waste-bearing fill material consisting of silt, sand, and gravel mixtures with broken asphalt, rock, concrete, brick, wood and metal debris. Investigations revealed soils with concentrations of TPH, lead, mercury, and polycyclic aromatic hydrocarbons (PAHs) that exceeded Washington State Model Toxics Control Act cleanup criteria.
This restoration site is in one of the last oxbows remaining from the original Duwamish River. In 1999, construction of a protective outer berm occurred, armoring and modifying the shoreline. The site has been restored but needs improvement to function as originally intended. This would be adaptive management of an older restoration project. Fish use within the site is low compared to other off channel habitats based on several years of sampling by UW. UW suggests the outlet opening is too narrow and long, making it hard for fish to find and access. The elevation of the backwater was set higher than we would recommend at this point. This was how several backwaters were created in this era, but we recognize now that the area is dewatered for large portions of the tidal cycle, and we think deepening it will increase accessibility, usability and overall habitat value. Site design did not address human access and activities, both of which have become issues that need to be addressed in any upland and access redesign. The proposed project would shorten, expand and realign the channel opening, remove shoreline armor, deepen channels within the intertidal estuary so that the area is inundated over a broader range of the tidal cycle and consider a bridge over the channel for recreational access. The requested funding is for the preliminary design phase of the project.