REGION 10 DIVE TEAM
www.epa.gov/region10/dive
EPA Region 10 Dive Team
Capping Contaminated Sediments (Denny Way Combined Sewer Overflow, Seattle, WA)
What: The EPA Region 10 Dive Team assisted the regional Water Resources Assessment Section
by evaluating the capping of contaminated marine sediment in Elliott Bay in front of the Denny
Way combined sewer overflow (CSO). Cap materials were clean upriver sands from the Duwamish
River.
Why: Diver survey objectives were to: 1) describe the physical nature of the cap, 2) document
conditions on the perimeter of the cap, and 3) evaluate colonization of the cap.
Where: Myrtle Edwards Park, Seattle waterfront, Washington. Approx. 47° 37' 04.7" Lat; 122° 21'
36.5 Long.
When: The 3-ft cap covering 3 acres was completed March 30, 1990. Dive surveys were conducted
May 16, 1990.
How: Diver investigations included photographing and videotaping biota and sediment type along
transects placed on top and adjacent to the cap.
Results: The cap was compact sand in a series of rolling mounds (4-6 ft relief). The surface was
covered by an easily suspended organic deposit. Leaves and golf balls were common. Infauna
appeared to be absent but mobile epifauna were common (crabs, sea stars, flatfish, nudibranchs,
etc.).
More Details: Internal agency reports.
Contact: Rob Pedersen at Dedersen.rob@eDa.aov
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