Former Metals Refinishing Facility, Kent, Washington

PES has provided consulting services at a former metals refinishing facility in Kent, Washington as the prime contractor since 2002, and PES personnel have been working on the site since 1997.

During metals refinishing operations, a variety of wastes were treated, stored, and disposed on a 4.2-acre portion of the site. RCRA closure of all regulated units occurred in 1987 and 1988. Under a RCRA post-closure permit, a groundwater extraction system began operation to extract chlorinated solvents in groundwater in 1992. PES personnel have operated, maintained, optimized, and replaced this system with a more cost-effective treatment system. To replace the system, PES characterized the nature and extent of the contaminant source and its impact to soils and multiple aquifers at the site during a remedial investigation.

During the feasibility study, remediation technologies (situ oxidation, in situ thermal treatment, enhanced bioremediation, and surface flushing) and containment technologies (e.g., slurry walls, sealed sheet piling, and permeable reactive barriers) were evaluated. From this evaluation, an innovative passive treatment alternative was selected, which includes a soil-bentonite wall around the site to contain the shallow aquifer, a reactor vault containing zero-valent iron to treat groundwater, and a gravity drainage system to induce groundwater flow out of the containment system to the sewer.

The soil-bentonite wall at the perimeter of the site and the below-grade passive treatment system were installed in September-November 2011. The design and location of the treatment system will facilitate redevelopment of the site in the future by eliminating the need for an above-grade treatment system, and the passive treatment system will minimize long-term O&M costs.

Throughout the course of the project, PES has worked with the site owner and Department of Ecology to maintain the project schedule to meet required milestones. PES has effectively managed stakeholder input and concerns to address concerns while maximizing project efficiency and PES has performed all work at the site in a safe manner without a reportable incident.