ARCHIVED REPORTS XR0007241 - Laserfiche WebLink

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Iw v N 1 - . ll A S S O C I A T E S I M C [9,500 mllgrams per kilograms (rng/kg)], toluene (65 mg/kg), ethyl benzene (82 mg/kg), and xylenes (470 mg/kg) The petroleum hydrocarbons appear to attenuate rapidly with depth as indicated by soil samples collected from SBI at 45 5 feet bgs and SB2 at a concentration of 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 SB I 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 1 Petroleum hydrocarbon constituents, including TPHg and BTEX, were detected in initial groundwater grab samples collected from borings SB 1 and S132 Only benzene, which was reported at concentrations of 7 6 ug/l and 12 ug/l, exceeded California's Maximum Contaminant ' Level (MCL) for drinking water iIn correspondence dated October 9, 1998, San Joaquin County Public Health Services, 1 Environmental Health Division (PHD/EHD) requested additional work be performed at the project site ' On June 15 and 16, 1999, a total of three soil borings (MW 1 through MW3) were advanced at the site in the vicinity of the closed in place or former USTs to evaluate the lateral extent of petroleum affected soil and groundwater Following soil sample collection the borings were completed as groundwater monitoring wells The initial sampling of the on-site wells indicated only low levels of petroleum hydrocarbons were present in the groundwater sample collected from MW-I On October 26, 2001, ATC submitted a request for closure The San Joaquin County ' Environmental Health Department (SJCEHD) requested that an additional monitoring event be performed ATC has conducted groundwater monitoring at the site beginning in June 1999 and continuing 1 through April 2004 Laboratory analytical data indicate that TPHg and benzene, toluene, ethyl benzene, and xylenes (BTEX) have been consistently detected at low levels in samples collected 1 from well MW-1, 1,2-dichloroethane (1,2-DCA) was detected in samples collected from wells MW-1 and MW-3 during the second quarter 2004 sampling event, and MTBE and the remaining fuel oxygenates other than 1,2-DCA have never been detected in samples collected from wells ' MW-1, MW-2, and MW-3 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 w 1148851reporls\Sum2004 doe 2