ARCHIVED REPORTS XR0007243 - Laserfiche WebLink

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A S S O C I A T E S I N C petroleum hydrocarbons appear to attenuate rapidly with depth as indicated greatest by soil samples from SBI at 45 5 feet bgs and SB2 at 55 5 feet bgs which contained only trace or nondetectable concentrations of petroleum hydrocarbons Total lead was detected at 5 5 mg/kg in the soil sample collected from SBI at 25 5 feet bgs Neither benzene nor fuel oxygenate additives were detected above laboratory method detection limits in any of the soil samples analyzed Petroleum hydrocarbon constituents, including TPHg and benzene, toluene, ethylbenzene, and xylenes (BTEX), were detected in initial groundwater grab samples collected from borings SBI and SB2 Only benzene, which was detected at concentrations of 7 6 parts per billion (ppb) and 12 ppb, exceeded California's Maximum Contaminant Level (MCL) for drinking water On June 15 and 16, 1999, a total of three soil borings (MW-1 through MW-3) were advanced at the site in the vicinity of the closed in place or former USTs to evaluate determine the lateral extent of petroleum affected soil and groundwater Following soil sample collection the borings were completed as groundwater morutoring wells The initial sampling of the on-site wells indicated only low levels of petroleum hydrocarbons were present in MW-1 On October 26, 2001, ATC submitted a request for closure The San Joaquin County Environmental Health Department (SCJEHD) requested that an additional monitoring event be performed ATC has conducted groundwater monitoring at the site beginning in June 1999 and continuing through March 2003 Laboratory analytical data indicates that TPHg and BTEX have been consistently detected at low levels in well MW-1, that 1,2-dichloroethane (1,2-DCA) has been detected in wells MW-I, MW-2, and MW-3 during the fourth quarter 2001 sampling event, and that 1,2-DCA was detected in wells MW-1 and MW-3 during the first quarter 2003 sampling event The SJCEHD issued a letter to Ms Lolly Bozzano on September 11, 2003 and concluded that due to the continuing presence of TPHg, and BTEX in groundwater samples collected from monitoring well MW-1 and the presence of 1,2-DCA in groundwater samples collected from wells MW-1 and MW-3, further investigation of the site is warranted Additionally, the SJCEHD reviewed the Closure Report for the site prepared in 2001 by ATC and discussed the contents with the CVRWQCB The CVRWQCB felt that the mass of contamination remaining in the soil was higher than the mass calculated in the report and that the feasibility of vapor extraction should be evaluated to remediate the contamination remaining in the soil that could continue to be a source of contaminant impact to groundwater Based on their review, the SJCEHD requested a work plan to investigate the lateral and vertical extent of the contamination at the site and to evaluate remedial alternatives for cleanup of the site w k14885Vcporu\2qu2004 doc 2