Bothell Service Center Simon & Son

The Washington State Department of Ecology (Ecology) and the City of Bothell (City) continue to clean up groundwater contaminated with dry cleaning solvents.  Under the Cleanup Action Plan (CAP), the preferred remedial alternative was Electrical Resistive Heating/Bioremediation with Groundwater Recirculation, augmented by targeted soil excavation and soil vapor extraction. The following has been accomplished:

• Electrical Resistive Heating was carried out at the source of contamination from May 29,     2018 to November 20, 2018. An estimated 1,466.5 pounds of tetrachloroethylene (PCE)   was removed from the ground.

• Soil vapor extraction (SVE), a process that removes contaminant (in the form of gasses)   from soil by applying a vacuum, was carried out from March 15, 2019 to August 30, 2019.

• Soil excavations at the source area vadose zone (soil zone above the water table) was   carried out from June 18, 2019 to August 28, 2019. Clean fill along with Carbstrate (a   harmless substance that enhances microbiological cleanup of contaminants).

• Bioremediation with Groundwater Recirculation which extracts groundwater, removes   contamination using an above ground system, then re-injects it with Carbstrate back into   the ground to clean up groundwater using microbiological processes. This bioremediation   and groundwater recirculation system began in October and is still operating.

• Groundwater monitoring to keep tabs on the cleanup of the groundwater contamination. 

A significant amount of soil and groundwater cleanup has been accomplished. At present, only the bioremediation system is operating on the remaining solvent plume, which has decreased in size and concentrations.

Lot D redevelopment
Portions of the BSCSS and the Bothell Former Hertz sites has been reparceled in the Lot D property, requiring modifications to the monitoring well network and the recirculating bioremediation system. Safeguards are in place to protect residents and workers in the redeveloped property, such institutional controls on land use, vapor barriers and vapor mitigation such as venting to prevent vapor intrusion risks to indoor air quality, and indoor air monitoring. However, since a large mass of contamination has already been removed, any human health risks from remaining contamination in groundwater are considered to be minimal or nonexistent.

Institutional controls on land use are under a May 13, 2020 environmental covenant.