Salt Marsh Restoration Project at Duwamish Turning Basin No. 3

This project consisted of the construction of the Duwamish River Turning Basin 3 Salt Marsh Restoration Project Site in Tukwila, Washington. Located at 10054 West Marginal Way South in Tukwila, Washington, the project existed on lands wholly owned by the Muckleshoot Indian Tribe.

The scope of work for this project included complete habitat and salt marsh restoration of the site, involving removal and disposal of surface debris, ecology blocks, concrete foundations, buried debris, slab materials and sidewalks. Extensive demolition and proper disposal of preservative treated wood was completed, including the removal of an entire footbridge and its supports. Removal of drainage structures, a wood retaining wall and fencing, removal of dolphins, complete removal of a dock and associated pilings, and demolition and disposal of two partially submerged barges also took place on the site.

The specific elements of work in the project included, but were not limited to: construction surveying and staking, clearing and grubbing, demolition and debris removal, removal of existing wood pilings and the corresponding wood bulk head wall from within the main channel of the stream, earthwork and grading, disposal of excess site material, and soil preparation to allow planting. Both temporary and permanent erosion control measures were implemented, including the use of floating geotextile silt curtains, 7’ high wire backed geotextile silt fencing, certified weed free straw bales, grade control structures, check dams, gravel, and boulders.

In addition, the site contained a warehouse structure scheduled for demolition. Approximately 40 feet wide by 60 feet long, the building is constructed of a corrugated metal military type Quonset Hut. Eexperience in handling dangerous materials was useful, as the exterior roofing and other materials within the building have been identified as containing asbestos. All asbestos-containing material was removed and legally disposed of prior to building demolition.

Other challenges present within this project included the protection and care of designated trees and shrubs within the site, dust control, road and marine traffic control, tidal influx control, and implementation of extensive erosion and runoff controls.

Additional challenges included traffic control, establishment of on-site utilities, and the removal and disposal of an in-water bulkhead to be completed without disturbing existing vegetation designated to remain.

Project Performance

Construction and installation of a marsh bench was also completed, as well as the installation of four eighteen inch diameter fish net poles, installed using vibratory methods for minimal environmental impact. Landscaping appropriate to the habitat was installed the following spring to complete the project.