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. 26 December 2001 ' AGE-NC Project No 97-0290 Page 7 of S ' 4 0 SUMMARY AND CONCLUSIONS Based on the data collected from the site, AGE finds • Ground water was encountered in the monitoring wells at approximately 45 feet bsg and was ' inferred to have a southerly flow direction during the February 2001 monitoring event • The highest concentrations of dissolved petroleum hydrocarbons were detected in samples ' collected from wells MW-2 and MW-4 • Concentrations of benzene have decreased in well MW-4 over the past quarter, yet remained significant at well MW-2(on-site) Benzene was detected in wells MW-2,MW-4, MW-6 and ' MW-7 at concentrations exceeding the State of California -Department of Health Services maximum contaminant level (MCL) of 1 0,ugll • Dissolved petroleum hydrocarbons of concern were not detected in samples collected from well MW-1 • The extraction of approximately 1,600 gallons of hydrocarbons as gasoline and BTEX was ' documented during the fourth quarter of 2000 and through the early second quarter of 2001 Continued operation of the SVE should result in diminishing recovery, signifying a reduction ' of the hydrocarbon impact to soil 5.0. RECOMMENDATIONS Based on the findings of the environmental activities recounted in this report, • AGE recommends monthly monitoring of the SVE/IAS operation I • AGE recommends the additional use of an oxygen release compound in wells MW-4 and possible MW-5, to stimulate microbial metabolism of petroleum hydrocarbons, which may reduce the off-site concentration of BTEX, specifically benzene in well MW-4 • AGE further recommends reduction of the quarterly ground water monitoring for the site to only wells MW-2 through MW-6 Due to the consistent lack of fuel additive detection, AGE proposes only to sample and analyze for TPH-g with BTEX • The next sampling event should be scheduled as soon as possible 1 Advanced CeoEnvironmental,Inc