EVS Modeling, Risk Assessment, and Remediation of Chlorinated Solvents Using In Situ Soil Vapor Extraction

The industrial Site is located in the greater area and measures approximately 1.5 acres in size. The Site was formerly used as a thermostat manufacturer and is currently used to manufacture glass panels and glass products. Field work activities involved the collection of 150 soil-gas samples from 60 soil-gas locations and 250 soil samples from 40 soil matrix locations.

Based on soil-gas and soil sampling results, the soil is impacted with chlorinated volatile organic compounds (VOCs), primarily tetrachloroethene (PCE), trichloroethene (TCE) and benzene up to a maximum depth of 60 feet below ground surface (bgs). The presence of these elevated VOC concentrations is a result of former industrial operations and historical releases at the Site, which are above the risk-based screening levels (RBSLs). Analytical data was modeled using C-TECH® Environmental Visualization System (EVS) Professional software to generate 3-dimensional (3-D) subsurface VOC plumes of soil-gas and soil matrix. Selected 3-D exhibits generated using EVS software including plan views and oblique views of the plumes will be displayed for the Site. The primary VOC “risk drivers” (>1E-06) in soil and soil gas were identified as PCE and TCE. Potential migration of VOC vapors to indoor air was estimated using the Johnson and Ettinger (J&E) vapor intrusion model modified to incorporate DTSC toxicity values for residential exposures, and using site-specific soil physical parameter values. The total cancer risk from indoor inhalation of VOCs from underlying impacted soil was evaluated using the results of soil matrix and soil-gas samples collected at the Site. The total cancer risk was estimated at 1.2 x 10-04, exceeding the DTSC target risk-screening goal of 1.0 x 10-06.