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I s +s w •�x (0 064 mg/kg) and xylenes (0 012 mg/kg) were detected at approximately 30 feet bgs in one boring, the maximum depth explored Attempts were made to further advance the Geoprobe unit in several of the borings, however probe refusal was encountered at depths ranging from approximately 16 to 30 feet bgs due to the hardness of the formation The results of the subsurface investigation were summarized in Smith Technology's Summary Report, Subsurface Investigation, dated December 22, 1997 In April 1999, at the request of PHS/EHD, ATC completed a receptor survey for the subject property ATC reviewed PHS/EHDI groundwater well"c'onstruction logs, Department of Water Resources (DWR) groundwater well construction logs, and conducted a site walk in the vicinity of the site to identify any groundwater wells located within a 2,000-foot radius of the site This survey revealed fourteen wells located within approximately 2,000 feet of the site -The closest of these wells is located approximately 800 feet upgradient of the project site The receptor survey findings are summarized in ATC's Well Survey for Andrew and Edith Trust,for the Pioperty at 1112 East Harding Way, Stockton, California, dated Apn19, 1999 On April 11, 2000, a single soil boring (SB7) was advanced to approximately 65 ft bgs to evaluate whether groundwater had been impacted at the subject site Groundwater was initially encountered at approximately 45 feet bgs and a sample was subsequently collected from the soil boring using a Hydropunch0 groundwater-sampling tool In order to determine~the vertical extent of contamination in the most cost-effective manner, the soil boring was further advanced to a total completion depth of 66 5 ft bgs where field observations suggested the vertical extent of the petroleum hydrocarbons had been realized Analytical results and field obser,,ations indicated that soil and groundwater beneath the location of the former USTs were impacted by residual--petroleum—hydrocarbon--constituents The vertical_extent_of—unpacted_sod—and groundwater appeared to be defined However, the lateral extent of petroleum hydrocarbon constituents at or near the groundwater interface was undefined Additional work to further characterize the extent of contamination was been requested PHS/EHD in correspondence dated September 20, 2000 1 On November 15 and 16, 2001, ars ATC geologist supervised the advancement of three soil borings to approximately 54 to 55 feet bgs Soil borings were then completed as groundwater monitoring wells MWI, MW2, and MW3 The soil sample collected from boring MW2 at a depth of 35 5 feet bgs contained the highest concentrations of TPHg, ethyl benzene, and xylenes The soil samples coflected from boring MW2 at depths of 30 feet bgs and 55 feet bgs contained only trace concentrations of TPHg, ethyl benzene, and/or xylenes The soil samples collected from borings MW 1 and MW3 at depths of 35 feet bgs contained trace concentrations of xylenes and TPHg, respectively The samples collected from borings MWI and MW3 at depths of 40 feet bgs did not contain detectable concentrations of TPHg or BTEX MTBE, t-amyl methyl ether (TAME), t-butanol (TBA), ethyl t-butyl ether (ETBE), di-isopropyl_ ether (DIPE), 1,2- dichloroethane (1,2-DCA), or 1,2-dibromoethane (EDB) were not detected in any soil samples collected from borings MWI, MW2, and MW3, though the detection limits were elevated in the MW2 sample from 35 5 feet bgs due to the high concentrations of TPHg noted previously S IEnviromcnta11224931reportslSUMrV doe 2