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SECTICNFOUR Conclusions and Recommendations <br /> 4.1 CONCLUSIONS <br /> Based upon our review of field exploration and laboratory analysis of soil and groundwater <br /> samples collected at the 1645 Cherokee Lane site during this investigation, we conclude the <br /> following <br /> 4.1.1 Evaluation of Soil Conditions <br /> o Reported concentrations of TPH-diesel exceed the 1,000 mg/kg standard, generally used by <br /> regulatory agencies as the criteria above which corrective measures are required That <br /> concentration is exceeded in samples from 10-ft to 40-ft bgs in Boring B-1, and at 25-ft and <br /> 31-ft bgs in Boring B-5 Soil from below this depth in B-5 may also exceed the 1,000 mg/kg <br /> standard <br /> o All ethylbenzene concentrations are less than the 230 mg/kg PRG (USEPA Preliminary <br /> Remediation Goal) for industrial soil <br /> o All total-xylenes concentrations are less than the 370 mg/kg PRG for industrial soil <br /> o Benzene toluene and MTBE were not detected in any soil sample <br /> o Impacted soil appears to extend to a depth of about 45-ft bgs Soil at 51-ft bgs showed only a <br /> trace concentration of xylenes <br /> 41 2 Evaluation of Groundwater Conditions <br /> o The laboratory reported detections of TPH diesel at 94,000 mg/l in groundwater from the <br /> site The 12,000 mg/l of TPH-gasoline reported probably represents short-chain constituents <br /> of diesel fuel <br /> o The laboratory reported detection of 28 gg/l benzene exceeds the California State MCL for <br /> drinking water of 1 gg/l <br /> a The laboratory reported detection of 22 gg/l toluene is less than the California State MCL for <br /> drinking water of 150 gg/1, <br /> o The laboratory reported detection of 550 gg/l ethylbenzene is less than the California State <br /> MCL for drinking water of 700 gg/l <br /> o The laboratory reported detection of 2,400 gg/l total-xylenes exceeds the California State <br /> MCL for drinking water of 1,750 gg/l, <br /> 4.2 RECOMMENDATIONS <br /> Because drinking water MCLs have been exceeded for benzene and xylenes in site groundwater, <br /> and soil is present with TPH-diesel concentrations exceeding 1,000 mg/kg, a Phase lI <br /> investigation should be conduced to assess the lateral extent of impacted soil and groundwater <br /> URS Greiner Woodward Clyde 11099670491UST REPORT CHEROKEE DOC122 SEP 99N\OAK 4-1 <br />