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enviroso In September 1995, four geoprobes (GEOI through GEO4), were driven to depths up to 56 feet below grade (fbg) and sampled. Soil samples obtained from these probes contained TPH-G ranging from ND to 7000 ppm and benzene ranging from ND to 10 ppm. These soil data were obtained from samples collected from depths ranging from 16 to 49 fbg. Soil data are summarized on Table 1. Soil Data Summary It appears that petroleum hydrocarbons in soil are primarily contained within a limited area beneath the former USTs complex and along portions of the former product piping(3 fbg). Petroleum hydrocarbons were not detected in unsaturated soils analyzed from well boring MW-3, boring B-6 and geoprobes GEO1 and GEO4, located down-gradient from the former USTs location. Petroleum hydrocarbons were not detected in unsaturated soils analyzed from up-gradient well borings MW-I and MW-2, Borings B-2 and B-5, and geoprobe GEO3. Petroleum hydrocarbons were also not detected in unsaturated soils analyzed from the new USTs location; Borings B-1, B-9, B-10, B-11, B-12, B-13 and B-14. Ground Water Data Summary Quarterly monitoring and sampling data from monitoring wells MW-1 through MW-3 indicate that petroleum hydrocarbons are present in ground water primarily to the south-southeast of the former USTs. Ground water samples from GEO1 and GEO4 contained 6900 and 8800 parts per billion (ppb) benzene, respectively. Ground water samples from GEO2, located within the former UST complex, contained 9800 ppb benzene. Geoprobe GEO3 ground water samples contained 4100 ppb benzene. Distribution of benzene in ground water is presented on Figure 3. Ground water flow direction appears to be toward the south-southeast. Depth to ground water in the fourth quarter of 1995 ranged from 47.60 to 48.76 below top of well casings. Prior Vapor Extraction Feasibility Testing During the vapor extraction feasibility test performed in late 1991 and 1992, soil vapors were removed from wells VEW-1,VEW-2 and MW-3. Wells VEW-1 and VEW-2 and associated piping, were installed to mitigate petroleum hydrocarbons in soils beneath the former USTs. Vapor extraction piping locations and configuration are presented on Figure 6. As shown, horizontal piping was also installed below grade to address shallow petroleum hydrocarbons in soils along product piping and adjacent to dispenser islands. The vapor extraction test ran for approximately two weeks. The initial vapor-phase TPH-G concentrations ranged from 76,000 to 81,000 parts per million volume (ppmv). During the test, airflow rates as high as 113 cubic feet per minute were measured. After two weeks of operation, vapor-phase TPH-G concentrations decreased to 2300 ppmv. Vacuum influence ranging from 0.17 to 0.4 inches of water column was measured in wells MWA,MW-2 and MW-3. These measurements were collected while extracting vapors from wells VEW-1 or VEW-2, or from both wells simultaneously, at a manifold vacuum ranging from 22 to 26 inches of water column. Results of the vapor extraction test indicate it is a viable option for remediation of petroleum hydrocarbons in soil and ground water beneath the subject site. 96374 2