Lockheed Shipyard Capping and Shoreline Restoration

The Lockheed Shipyard Sediment Operable Unit (LSSOU) is located approximately 2 miles (3.2 km) south of Seattle within the West Duwamish Waterway adjacent to Harbor Island. Figure 1 shows the project site which extends 1,600 ft (488 m) along the east shoreline of the West Waterway. Sediment at the LSSOU intertidal areas beneath piers and shipways was contaminated from former shipyard operations. The complexity of project site physical processes, extent of dredging, and strict regulatory requirements on the clean-up action necessitated an innovative approach to capping and backfilling the project site shoreline areas. The clean-up action included dredging and partial removal of contaminated material, capping the residual surface with a combination of armor and habitat layers. The clean-up action also included installation of a rock revetment with toe buttress and restoration of shoreline and intertidal features. Coastal engineering analysis was conducted to properly understand physical processes acting at the site for existing conditions and with the alternative designs and to develop design criteria that meet the project objectives and expectations. The coastal engineering analysis included determination of wind-waves, vessel wakes, vessel propeller wash, and wave swash impacts.