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1 <br /> 05 November 1997 <br /> AGE-NC Project No 96-0249 <br />' Page 6 of 7 <br />' • Laboratory and field data suggest extensive petroleum hydrocarbon-impacted ground water <br /> is present near the UST area (PI through P3) and the dispenser island area (P4) <br /> • Laboratory analysis of grab ground water samples collected from P 1 through P4 suggests that <br />' the highest concentration of dissolved TPH-g is near P3 (Figure 4), laboratory analysis <br /> suggests that the highest concentration dissolved TPH-d is encountered near P2 and P4 <br /> (Figure 5) <br />' • An immiscible, lighter-than-water sheen on water samples P2-H20, P3-H20 and P4-H20 <br /> noted in the laboratory report indicates the possible presence of free product in the area <br />' • The State of California drinking water standards, adopted by the Safe Drinking Water Act, <br /> have established maximum contaminant levels (MCLS)for benzene, toluene, ethylbenzene and <br />' xylenes at 1 ppb, 150 ppb, 700 ppb and 1,750 ppb, respectively Concentrations of BTE&X <br /> compounds detected in the grab ground water samples collected from PI through P4 were <br /> above MCLS <br />' • Laboratory analysis of grab ground water samples from P-I through P-4 detected TPH-d at <br /> concentrations between 5,700 to 530,000 ppb The Central Valley Regional Water Quality <br /> Control Board has declared enforceable limits for TPH-d based on the USEPA"Suggested <br /> No Adverse Response Level (SNARL)" of 100 ppb <br /> 60 RECOMMENDATIONS <br /> Based upon data collected from the site, AGE recommends <br /> • Additional investigation to determine the lateral and vertical extent of hydrocarbon-impacted <br />' soil and ground water at the site Further assessment is wai ranted north, south, east and west <br /> from the known petroleum hydrocarbon-impacted area <br />' • The installation of ground water monitoring wells to provide repeatable ground water <br /> sampling locations, determine site-specific ground water flow direction and gradient and to <br /> document petroleum hydrocarbon concentration trends <br /> 1 70 LIMITATIONS <br /> Our professional services were performed using that degree of care and skill ordinarily exercised by <br />' environmental consultants practicing iii this or similar localities The findings were based mainly upon <br /> analytical results provided by an independent laboratory Evaluations of the geologic/hydrogeologic <br /> conditions at the site for the purpose of this investigation are made from a limited number of available <br /> Advanced GecEm ironmental,Inc <br />