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Mr. Steve Sasson Project 22794-100.001 <br /> August 10, 1998 <br /> Page 7 <br /> Benzene was detected in only one soil sample at a concentration of 0.002 mg/kg. Low <br /> levels of benzene, toluene, and ethylbenzene were detected in groundwater samples at <br /> concentrations of 0 8 gg/L benzene,0.7 to 1.1 µg/L toluene, and 10 gg/L ethylbenzene. <br /> Soil impacts identified in the vicinity of the former UST complex extended to depths of <br /> approximately 20 feet bgs. Borings drilled south and southwest of the former UST <br /> complex identified impacts at 30 feet bgs. Samples collected at depths between 34 and <br /> 42.5 feet bgs did not contain detectable concentrations of TPHD (see Figures 3 and 4). <br /> As shown on Figures 5 and 6, groundwater impacts identified in on-site and off-site <br /> monitoring wells and HydroPunch samples ranged from <1 to 160,000 gg/L TPHD. <br /> Highest detected concentration was in the 1991 HydroPunch groundwater sample from <br /> B-19 collected offsite. The distribution of impacts identified in the 1991 assessment <br /> suggests sources other than the former Safeway USTs are contributing to groundwater <br /> impacts The highest detected concentration m 1995 HydroPunch samples was <br /> 1,200 µg/L The groundwater samples collected in the northwest part of the site and <br /> intended to represent background conditions contained 300 µg/L and 420 Rg/L TPHD in <br /> KHP-2 and KHP-3, respectively. These samples, collected upgradient of the former UST <br /> location, suggest other sources of groundwater impact are present in the vicinity of the <br /> former Safeway facility <br /> Samples collected from wells MW 4 through MW-6 and HydroPunch locations <br /> completed in a sand unit below 25 feet bgs contained the highest TPHD concentrations. <br /> The locations of wells MW-4 and MW-6 are upgradient and crossgradient of the former <br /> Safeway USTs, respectively In previous reports (Krazan, 1995, Safeway, 1996), these <br /> results were interpreted to indicate regional groundwater impacts. <br /> PETROLEUM HYDROCARBON MASS ESTIMATES <br /> Analytical results collected from prior site characterization and monitoring activities were <br /> used to estimate the mass of TPHD in soil and groundwater. The mass of BTEX <br /> constituents and PNA constituents were not calculated based upon very limited <br /> detections. Mass calculation sheets are presented in Appendix C. <br /> Mass Removed by Soil Excavation <br /> Soil excavation activities in 1987 and 1988 removed approximately 1,200 cubic yards of <br /> petroleum hydrocarbon-impacted soil. Characterization of the extracted materials <br /> indicated the TPHD concentrations ranged from approxirnately 18 to 140 mg/kg per <br /> SACN\PJZ2794\279410001CS-99V=smer8 Emcon <br /> Rev 0.8110198 <br />