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C A M B R I A 0 these wells and from previous soil borings drilled in the UST area suggested the USTs are likely the primary source area for petroleum hydrocarbons and MTBE detected in groundwater beneath this site The findings of this investigation are documented in Cambria's February 10, 2000 Site InvestigationJFourth Quarter 1999 Groundwater Monitoring Report 2000 Hoist and Waste Oil UST Removal. During November 2000, one 550-gallon waste oil UST and two hydraulic hoists were removed Cambria collected one soil sample from beneath the waste oil tank and one sample beneath each hoist No petroleum hydrocarbons, fuel oxygenates, halogenated volatile organic compounds,or polychlorinated biphenyls were detected in soil samples collected from beneath the former waste oil UST Total chromium, nickel, and zinc were detected in soil beneath the waste oil tank at concentrations well below hazardous levels Samples collected beneath the hoists were analyzed for total recoverable petroleum hydrocarbons (TRPH) The sample collected from the northwestern hoist contained 820 ppm TRPH Soil from beneath the other hoist did not contain detectable concentrations of TRPH Complete results of waste oil UST and hoist removals are documented in Cambria's December 15, 2000 Waste Oil Tank/Hoist Removal Report Well Survey: A well survey was submitted to San Joaquin County Public Health Services, Environmental Health Division during our June 19, 2001 meeting Only one water supply well was identified within half a mile from the subject site It is a domestic well located approximately one-half mile southwest of the site(Figure 1) 2001 Soil Borings During October 2001, Cambria advanced six cone penetration test (CPT) borings Borings CPT-1 and CPT-2, drilled south of the USTs, delineate the vertical extent of petroleum hydrocarbons and fuel oxygenates in soil Groundwater samples were collected from boring CPT-1, near the USTs, and from borings CPT-2 through CPT-6, to assess the lateral impact to groundwater MTBE was detected in groundwater from all the bonngs at concentrations ranging from 2 8 to 390,000 parts per billion(ppb), with the highest concentration in CPT-5 TPHg, tertiary butanol (TBA), tertiary amyl methyl ether (TAME), and ethyl tertiary butyl ether (ETBE) were also detected in groundwater from some of the borings Complete investigation results are documented in Cambria's April 18, 2002 Site Investigation Report and Site Conceptual Model Groundwater Monitoring Program: Prior to this investigation, there were three monitoring wells located onsite (MW-1, MW-2, and MW-3), which are sampled quarterly During the second quarter 2002 sampling event, MTBE and TBA were detected in all three wells at concentrations ranging from 1,700 to 11,000 ppb and 60 to 2,000 ppb, respectively During the 0955 3