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Vapor Intrusion Assessment and Interim Action at Historic Metal Plating Site

The soil, groundwater, and soil vapor on this property is impacted by tetrachloroethene (PCE), trichloroethene (TCE), chromium III, and chromium VI. These impacts result from historical metal plating, electroplating, and polishing operations. Historical data confirm the presence of these compounds in soil and groundwater at concentrations exceeding the Model Toxics Control Act (MTCA) cleanup levels. These historical data also indicate that impacts to groundwater on the property extend off-site to the north and west, potentially following a pathway along a sewer line backfill.

Vapor Intrusion Assessment and Interim Action

Vapor Intrusion Assessment and Interim Action

TRC conducted a vapor intrusion assessment to assess the potential for environmental risks associated with vapor intrusion. Historical indoor air sampling results indicated that TCE in indoor air exceeded the allowable reasonable maximum exposure-based remediation level. TRC’s vapor intrusion assessment discovered concentrations of PCE and TCE in soil vapor that exceeded the site-specific soil gas screening level. Based on the vapor intrusion assessment results, TRC recommended mitigating the vapor intrusion risks on the property by leaving it vacant, installing a vapor intrusion mitigation system (VIMS), and conducting a remedial investigation and feasibility study (RI/FS) to characterize the extent of the impacts and develop a site-specific cleanup action plan.

TRC submitted a work plan for the VIMS to the Washington State Department of Ecology (Ecology) and received approval to proceed with the VIMS and subsequent RI/FS. TRC implemented the VIMS as an interim action and submitted the RI for Ecology approval. Environmental investigation is ongoing at the property and TRC expects to perform further assessment activities in order to gather enough data to characterize the extent of impacts to the property and any adjacent properties.

TRC also provided litigation support and expert witness testimony in defense of the proposed VIMS and remedial actions for an adjacent property.

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