Beneficial Uses
of Dredged Materials
Case Study: Jetty Island, Puget Sound
The U.S. Army Corps of Engineers (USAGE), Seattle District, and the Port of Everett, Washington,
collaborated on using dredged materials from a long-term dredging project maintaining navigation
channels. Placement of this dredged material was used for beach nourishment; more specifically it was used
to create a protective sand berm that allowed for the formation of saltmarsh, lagoon, and backshore dune
habitats on Jetty Island. Jetty Island is a 200-acre port-owned intertidal island at the mouth of the Snohomish
River. This beneficial use project was funded by the USAGE and the Port. Using normal operation and
maintenance (O&M) funds, the USAGE paid all costs for the dredging and disposal of maintenance dredged
materials. The Port of Everett obtained all necessary permits and funded biological baseline and monitoring
studies for the project.
Federal and state natural resource management agencies and the Tulalip Tribe assisted in planning and
meeting regulatory requirements. Agencies involved included the USAGE, U.S. Environmental Protection
Agency, U.S. Fish and Wildlife Service, NOAA's National Marine Fisheries Service, Washington Department
of Natural Resources, Washington Department of Ecology, and the Washington Department of Fish and
Wildlife. These agencies considered development of saltmarsh and other habitats to be mutually beneficial
and proceeded to create new feeding habitat for juvenile salmon.
The USAGE initially placed 323,000 cubic yards of material on the island during a 4-month construction pe-
riod, which was completed in January 1990. The close proximity of the dredging site to Jetty Island enabled
the use of hydraulic dredging rather than clamshell. It also made the project more economical in comparison
to open-water disposal. USAGE'S physical monitoring included annual topographic surveys. By 1999, the re-
sults from these physical monitoring surveys confirmed that the projected erosion rates for the newly con-
structed sand berm and risk for potential breaching or stormwater overtopping of the berm were accurate.
Biological monitoring data collected by the Port showed that saltmarsh habitat development greatly exceeded
expectations and thereby justified beach nourishment. The USAGE placed an additional 239,000 cubic yards
of dredged material to restore the berm width and elevation in January 1998. In the planning process for fu-
ture projects, project sponsors advise other project proponents to integrate all affected parties into planning
as early as possible. They also advise planning begin early, so that beneficial uses projects can be ready to
take advantage of funding for scheduled O&M navigation activities.
A number of the agencies participating in the Jetty Island project have continued their interest in and
commitment to the beneficial use of dredged materials by forming a beneficial uses group for Puget Sound
which has provided a forum for encouraging and coordinating beneficial use projects. The success of the
Jetty Island Project has helped pave the way for other beneficial use and mitigation projects.
Contact:
Hiram Arden
U.S. Army Corps of Engineers, Seattle District
(206) 764-3401
hiram.t.arden@usace.army.mil
U.S. Environmental Protection Agency EPA842-F-07-001B
U.S. Army Corps of Engineers October 2007
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