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0 <br /> These findings indicate that GWE, SVE, and natural attention processes have successfully <br /> reduced concentrations of petroleum hydrocarbons in soil and ground water beneath the <br /> site <br /> Recent Ground Water Monitoring Summary <br /> Ground water monitoring and sampling for the second quarter of 1997 was conducted on <br /> April 2, 1997 Groundwater samples from Wells MW-1, MW-2, RWA, and VEW-1 <br /> contained 0 81 ppb, 0 76 ppb, 6 3 ppb, and 1 5 ppb benzene, respectively The remaining <br /> wells were ND for benzene in ground water MTBE was detected in Wells MW-i through <br /> MW-5, RW-1, VEW-1, VEW-2, and VEW-4 Halogenated volatile organics (HVOCs) <br /> were detected in Wells MW-2, MW-3, MW-4, RW-1, RW-2, and VEW-3 Petroleum <br /> hydrocarbon analytical data are summarized in Table 2 and on Plate 3 HVOC analytical <br /> data are summarized in Table 3 and on Plate 4 <br /> Potential Chlorinated Solvent Sources <br /> Shell Oil Products Company formerly operated a service station at the site The service <br /> station was constructed in 1955 This construction included the installation of four 4,000- <br /> gallon underground storage tanks (USTs) used to store gasoline products and one 500- <br /> gallon UST used to store used motor oil In 1963, one of the 4,000-gallon USTs was <br /> removed and two 7,500-gallon USTs were installed to store gasoline products The station <br /> discontinued selling gasoline in 1981 and all five gasoline USTs were removed The waste <br /> oil UST remained in use at the site until June 1990 On June 1, 1990, the waste oil UST <br /> failed a precision tank test The contents of the waste oil tank were pumped out on June 5, <br /> 1990 In September 1990, a soil boring (SB 6) was drilled adjacent to the waste oil tank <br /> Soil samples collected at depths of 11 5, 21 5, 31 5, and 36 5 feet below grade (fbg) from <br /> Boring SB 6 were analyzed for TPH-diesel, TPH-gasoline, and BTEX Petroleum <br /> hydrocarbons were not detected in any of these soil samples The waste oil tank was <br /> removed in 1991 No data were available regarding the collection of soil samples during <br /> the waste oil tank removal <br /> Based on Shell's use of the site, the former waste oil tank appears to be the only potential <br /> on-site source of HVOCs While Shell does not have any soil sample data for HVOCs in <br /> the vicinity of the former waste oil tank, the distribution of HVOCs in ground water at the <br /> site indicate the former waste oil tank is not the source of HVOCs which have impacted <br /> ground water beneath the northern portion of the site Ground water samples collected <br /> from the wells nearest the former waste oil tank were ND for HVOCs (Plate 4) <br /> 97369 2 <br />