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\TAAT A S S O C I A T E S I N C ' feet bgs which contained only trace amounts of petroleum hydrocarbons or none above the laboratory detection limits Total lead was detected at 5 5 mg/kg from the soil sample collected from SBI at 25 5 feet bgs Neither benzene, fuel oxygenate additives, or VOCs were detected above laboratory method detection limits in any of the soil samples analyzed ' Of the soil samples collected from MW 1 through MW3, only two samples from boring MW 1 contained one or more analytes above the laboratory's method detection limits (MDLs) The sample collected at 30 5 feet bgs (BP-MW 1-30 5) contained toluene at 0 008 mg/kg, only ' marginally above the MDL of 0 005 mg/kg The sample collected at 40 5 feet bgs contained toluene at 0 010 mg/kg and xylenes at 0 021 mg/kg ' Benzene, ethylbenzene, MTBE, and the remaining fuel oxygenates were not detected above their respective MDLs in any samples ' 3.1.1 Dass Balance Calculations- Soil The lateral extent of petroleum hydrocarbons in soil is depicted on Figures 4 and 6 Soil analytical results are summarized in Table 1 Using the analytical results from the subsurface investigations presented in Table 1, ATC estimated the lateral extent of petroleum hydrocarbon concentrations in the unsaturated zone beneath the site as depicted on Figures 4 and 6 The total mass of TPHg remaining in the soil is estimated to be approximately 2,018 pounds or 917 kilograms The mass of benzene remaining in the soil appears to be negligible since it was not detected above laboratory method detection limits Mass balance calculations are included in Appendix B ' 3_2 Petroleum Hydrocarbons in Groundwater ' Petroleum hydrocarbon constituents, including TPHg and BTEX, were detected in hydropunch groundwater samples collected from borings SB 1 and SB2 Only benzene, which was reported at concentrations of 7 6 ug/l and 12 ug/l, respectively, exceeded California's Maximum Contaminant Level (MCL) for drinking water in these bonngs The MCL for benzene is 1 ug/l Total dissolved lead was detected at 1 1 ug/l and 1 6 ug/l in samples collected from borings SB 1 and SB2, respectively Fuel oxygenate additives were not detected above laboratory method detection limits in either of the two water samples analyzed ' Following the installation of the site's three monitoring wells, ATC initiated quarterly groundwater monitoring and sampling on June 25, 1999 This work included measuring the depth-to-water in wells MW 1 through MW3 and purging and sampling the water from these wells Min addition to the site's domestic well The initial sampling of the on-site wells indicated that only low levels of petroleum hydrocarbons were present in MW I Benzene was detected once at the MCL of 1 ugA Toluene, ethyl benzene, and xylenes were well below their respective MCLS Analytical results of water samples W 114885VepodslNFA-Request doe 4