International Dredging Review

International Dredging Review

Boeing recently completed a multi-faceted environmental restoration of a one-mile portion of the Duwamish Waterway removing contaminated sediments and creating acres of new aquatic habitat critical for endangered salmon migration as well as new vegetated marsh and riparian areas. The birthplace of the Boeing Company and the B-17 Flying Fortress bomber that was critical to national defense during World War II has been transformed by innovative remediation dredging methods (RDMs) developed for the project. These RDMs demonstrate that contaminated sediment can be removed efficiently without adverse release of chemicals to the water. The Duwamish Waterway area has gone from a camouflaged bomber plant that helped win World War II to an invaluable natural habitat. The project addressed more than a century of impacts from industrialization along the waterway and throughout the entire watershed.  


From tufted hairgrass and bulrush to willows and big leaf maple more than 170000 native plants now occupy five acres along the wa-ter’s edge on Boeing property.

Rather than work through traditional environmental restoration and remediation programs one after each other Boeing engaged multiple agencies and stakeholders to combine shoreline restoration and environmental dredging into a single project. The result was that environmental benefits were achieved more quickly with less disruption to the community. This resulted in Boeing receiving an Excellence in Restoration award from the National Oceanic and Atmospheric Administration (NOAA) for completing the largest single restoration project on the Duwamish Waterway. In addition the project has also been recognized by major stakeholders such as local residents and tribes and the US Environmental Protection Agency (EPA). 

Most recently in June at the World Dredging Congress & Exhibition (WODCON) held in Miami Florida the project was awarded the Environmental Excellence Award for “Environ-mental Dredging.” The project team members included The Boeing Company; Amec Foster Wheeler; Dalton Olmsted & Fuglevand Inc. (DOF); Envirocon Inc.; Quigg Bros. Inc.; Ballard Diving & Salvage; and Waste Management.


Working the “backyard” of local residents 24 hours per day required committed coordination.

Envirocon did precise mechanical dredging of 161000 cubic yards of contaminated sediment from more than one-half mile of the waterway at an active manufacturing facility. The company also performed shoreline excavation rehabilitation and restoration services more than five acres of contiguous intertidal wet-lands adjacent to this site. Both the project’s location – within an active navigable channel that flows directly through a major metropolitan city – and environmental sensitivities such as protecting fish species waterfowl and other wildlife and coordination with the Muckleshoot tribe during fishing activities – made careful collaboration essential.

The integration of cleanup with habitat restoration allowed the overall project to be completed in a shorter timeframe thereby reducing its impact on local residents and other waterway users during the construction phase and allowing the positive environmental benefits to occur sooner.


Boeing and its project team removed 265000 cubic yards of sediment and bank soil containing legacy contamination from the Lower Duwamish Waterway and replenished the waterway bed with clean sand.

Some of the highlights of the project include: 

• the dredging of 163000 cubic yards of contaminated sediment from the waterway using project-developed enhanced dredging approaches; 

• the elimination of release resuspension residuals (3Rs) normally associated with re-mediation dredging through newly developed remediation dredging methods; the removal of historic over-water buildings as well as 700 creosote treated pilings converting an industrial- debris covered and darkened shoreline to valuable intertidal habitat; 

• the excavation of 50000 cubic yards of intertidal and shoreline sediment soil and debris using excavation equipment; 

• the placement of 190000 cubic yards of sand and gravel to reshape the shoreline and waterway bed following dredging and excavation to establish environmentally valuable intertidal and subtidal habitat; 

• the creation or restoration of five acres of habitat for fish birds and other wildlife along this vital salmon migration corridor; and the planting of 170000 native plants.  


As excavated sediment is transported by barge on the Lower Duwamish Waterway it passes habitat created by Boeing to improve Puget Sound salmon runs.