TRS Group, Inc.

Remediation of TCE NAPL in active Alleyway Arlington, Texas - Case Study


Courtesy of TRS Group, Inc.

Goals to achieve separate analyte-specific clean-up goals in clay soils and groundwater respectively

Project Summary

TRS Group, Inc. (TRS) completed a Guaranteed Fixed Price Remediation (GFPR) of tetrachioroethene (PCE), trichioroethene (TCE), cis-l,2-dichloroethene (cis 1,2-DCE), 1,1,1-trichloroethane (1,1,1-TCA), 1,1-dichloroethene (1,1-DCE), 1,1-dichloroethane (1,1-DCA), methylene chloride, and Freon 113 in soil and groundwater in Newark, CA. The goals of the ERH remediation system were to achieve analyte-specific cleanup goals for PCE andTCE in the upper clay layer and for PCE, TCE, cis-l,2-DCE, 1,1-DCE, 1,1-DCA and vinyl chloride in shallow groundwater. The system incorporated 91 electrodes with co-located vapor recovery (VR) wells to treat a soil volume of approximately 20,800 cubic yards (yd3) across two treatment areas (TA-1 and TA-2). Active subsurface heating extended from approximately 0.5 feet below grade surface (ft bgs) to 20 ft bgs in TA-1 and approximately 0.5 ft bgs to 25 ft bgs in TA-2.

Average concentrations of PCE and TCE in soil decreased over 99.99%, two orders of magnitude more than the remedial goals, in the ERH treatment area following treatment. Thirteen out of the sixteen soil samples were below laboratory detection levels for PCE and TCE. Of the 45 groundwater samples collected, cleanup goals for all six compounds were met in all except three locations. Analysis of temperature trends in the final ERH treatment volume, groundwater analytical results from samples taken outside the treatment volume, and general site information indicated that concentrations within the ERH focus volume had reached the point of diminishing returns. Soil vapor and steam capture was complete throughout ERH system operations and site, staff, and public safety were maintained at all times.


The rectangular-shaped site is located in a mixed industrial and residential area and covers approximately 2.4 acres, as depicted in Figure 1. Residential properties are located to the north and east of the Site. The site contains an office building, two warehouses, a paved parking area, and a former tank farm for flammable and nonflammable liquids. The northernmost area is open and unpaved (former railroad spur). A number of vacant and/or abandoned industrial properties are located to the south and west of the Site.

The site operated as a permitted hazardous waste facility for storage and distribution of virgin chemical products and recovery of chlorinated and fluorinated solvents from 1973 to 1993. Cuirent operations at the site include storage and distribution of prepackaged virgin chemical products.

Site Characteristics & Design Parameters

Shallow stratigraphy across the site is generally consistent. Dry to moist fill material extends from the surface to approximately 2 - 4 ft bgs. A semi-confining upper silty clay layer beneath the fill extends to a depth of 11 or 12 ft bgs. The shallow groundwater zone (SGZ) consists primarily of silty sand and extends from 11 or 12 feet bgs down to 18 - 28 ft bgs. In some areas of the site, a narrow sandy gravel lens is present at the base of the SGZ. The Newark Aquitard is a silty clay unit extending from the base of the SGZ to 43 - 49 ft bgs. Saturated sands, silty sands, and silts of the Newark Aquifer are first encountered at 43 - 49 ft bgs. Groundwater was encountered between 11 -12 ft bgs.

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