A pair of street corners in Southeast Seattle may not look like much right now, but they’re already a first-of-its-kind cleanup site for Ecology. Yet, it’s a contaminated site much like hundreds before it that have undergone cleanup and been put to new use. We held a public comment period on a cleanup plan that marks an important an important step forward.
The Mount Baker Housing Association’s Maddux project is the inspiration for Washington’s Healthy Housing Remediation Program, which we developed in conjunction with the Washington State Department of Commerce. The program enables local governments and nonprofit organizations to obtain state funding to help offset environmental cleanup costs when redeveloping contaminated land for affordable housing.
Mount Baker acquired a cluster of lots where S. McClellan Street intersects with Martin Luther King Way S. The association plans 166 affordable units with street level retail a block from Sound Transit’s Mount Baker Link light rail station and near a variety of shopping and services.
Overcoming a common obstacle
These plans overlap with a costly problem that’s common to urban redevelopment. Previous use of the property — in this case a gas station and a dry cleaner — left contamination behind. The remediation program, building on earlier funding we’ve provided for the project’s cleanup, has enabled Mount Baker to proceed with more than $6 million in state assistance to hire consultants who evaluated the contamination, sifted through cleanup options and worked with us to propose a cleanup plan.
We’re asking the public, as part of the state Model Toxic Control Act cleanup process, to review those studies, the plan, proposed updates to our legal agreement with Mount Baker, and environmental review documents we’ve prepared.
That comment period ran through November 26, 2019.
Historic releases from gas stations and dry cleaners are the most common types of cleanup sites in Washington. Current laws on handling cleaning chemicals and managing underground storage tanks prevent these problems at today’s cleaners and fill-up stations.
A cleanup plan that fits the project
The gas station cleanup will primarily involve excavation of soil in and around areas where underground tanks and system piping once were.
The dry cleaner’s contamination requires a more complex approach. The solvents that were used mix readily into water. Even a small spill or leak into the ground can spread over a wide area if it enters the flow of groundwater. That’s what happened here (see the map below), and the Maddux development will incorporate features that factor in a cleanup process that may continue for several years.
Excavation of the contaminated soil under the dry cleaner and adjacent parcels will remove the source of the groundwater contamination. This will help slow or stop the expansion of the plume of solvent-contaminated groundwater that extends under S. McClellan Street, part of the former gas station and under an adjoining stretch of Martin Luther King Way S.
The rest of the plan allows the project to proceed and cleanup to continue without disrupting traffic on the two streets:
- Because the solvent compounds can release vapor that can rise through the soil, the project will be engineered with capping, vapor barriers and sub-slab ventilation. The property deed will prohibit future modifications that change these protections without notifying us and obtaining our approval.
- Long term monitoring will provide information on how well the cleanup treatments are working and track the breakdown of the solvents.
- After 5 years of monitoring, the time to reach cleanup in the groundwater will be recalculated. If it is determined to be too slow, Mount Baker will inject a chemical (such as zero valent iron) into the groundwater that aids in the breakdown the contaminants. Bacteria that’s naturally present in soil also helps by feeding on the solvent chemicals, breaking them down biologically.
We will review the monitoring data and the condition of the site every five years to determine how well the plan is working and whether any changes are needed. We’ll issue a report on these periodic reviews and ask for public comment each time.
Along with the comment period, we hosted a public meeting and open house. Our cleanup experts were there, along with representatives from Mount Baker and their environmental consultants.
We had displays about the project and the cleanup plan and discussed the cleanup and answered questions. We also gave a presentation and took audience questions. Translation and interpreter services were available in Spanish, Chinese, Vietnamese, and Khmer.
The documents out for comment:
A fact sheet about the project's cleanup process is available in: