The Unocal Edmonds site, prior to cleanup. (Photo courtesy of Chevron)
A former bulk fuel terminal site near downtown Edmonds has moved steadily through several cleanup phases since the 1990s. While petroleum and arsenic contamination have been treated and removed throughout most of the site, there are still a few areas that need remediation. Today we are releasing a study that looks at different options for cleaning up the remaining contamination and selects a preferred option, and we’d like your feedback.
The Unocal Edmonds cleanup site is located at 11720 Unoco Rd, Edmonds, about a mile southwest of the Edmonds ferry terminal. The site is owned by Unocal, a Chevron subsidiary, and was used as a fuel terminal from 1923-1991. There was also an asphalt plant on the site from 1953 through the late 1970s.
Aerial view of Unocal Edmonds cleanup site.
The site is divided into two sections, the Upper Yard and the Lower Yard. The cleanup of the Upper Yard was completed in 2003, and removed 100,000 tons of soil contaminated with metals and petroleum as well as 23 fuel storage tanks. This area was eventually redeveloped into the Point Edwards condominiums.
Remediation in the Lower Yard has occurred in several phases since 2001. A total of 190,000 tons of soil contaminated with metals and petroleum were removed from the Lower Yard. Cleanup of the Lower Yard is nearly complete.
Dual phase extraction
One of the remaining contaminated areas includes soil next to a stormwater pipe owned by the Washington State Department of Transportation. The pipe was designed to be held in place through tidal fluctuations by the weight of the soil over it, and previous attempts to remove the contaminated soil caused damage to the pipe.
Instead of removing the soil in that area, we have been using a technology called dual phase extraction to treat the contamination. This remedial technology uses pumps and a large vacuum to depress the water table. It extracts polluted groundwater through wells and treats it above ground, discharging clean water back into the soil. While the water table is depressed, a vacuum on the wells draws air movement through the impacted soil and removes the volatile pollutants in the soil gas. The air is treated before it is released above ground.
The dual phase extraction process has successfully removed pollutants near the pipe, with the remaining contamination bound to the soil. Due to the success observed in the treatment area around the pipe, this system was expanded to treat areas along Willow Creek.
What’s the plan for cleaning up?
In our feasibility study, we evaluated several options to clean up the remaining contamination in the Lower Yard and compared their costs and environmental benefits. We’re proposing to use a combination of excavation, dual phase extraction, and an environmental covenant (legal restriction on land use) to limit further contact with any remaining contamination.
Will the cleanup make the site usable for salmon habitat?
We understand there is community interest in restoring the Lower Yard for salmon habitat. While Ecology does not own the property and cannot determine how the land will be used, we will ensure cleanup levels are protective of aquatic life, plants, and wildlife (including organisms that live in the soil).
The study we are releasing today reflects the stricter ecological standards that will protect plants and wildlife surrounding the marsh. However, there are isolated areas of soil contamination below ground that are likely to remain at the site. Marsh restoration activities in these areas that change the topography of the site will need to abide by the legal guidance of the environmental covenant.
Public comment period
We are accepting public comments on the feasibility study and public participation plan starting at midnight on Sept. 9, 2024 through Nov. 24, 2024 at 11:59 p.m.
On Sept. 16, 2024, we will host an in-person open house followed by a hybrid public meeting to provide project information and answer questions. The meeting will be at Edmonds City Hall, Brackett Room, 3rd Floor, 121 5th Ave. N., Edmonds, WA.
- 5:30 p.m. – open house for in-person attendees
- 6:30 p.m. – presentation (in-person and online via Zoom) followed by Q&A
Please register in advance for the online presentation.