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C A M B R I A concentrations ranging from 0 021 to 0 13 ppm Complete investigation results are presented in Aegis' March 5, 1991 Monitoring Well Installation Results Report 1991 Monitoring Well Installation- During December 1991, one groundwater monitoring well (MW-4) was installed TPHg was detected in the soil sample collected from 29 lbg at 1 1 ppm Benzene, toluene, ethylbenzene, and xylenes (BTEX) were not detected in any of the soil samples collected from well boring MW-4 This investigation is summarized in Aegis' April 27, 1992 Hydrogeologic Assessment Results and Quarterly Groundwater Monitoring Report 1991-1992 Extended Pilot Vapor Extraction Test- Petroleum hydrocarbons were removed from soil beneath the former UST pit during a soil vapor extraction pilot test performed from December 1991 through January 1992 Air monitoring data indicated petroleum hydrocarbons at concentrations of up to 6,500 parts per million by volume were removed from soil during the test The test is documented in Aegis' January 6, 1992 and February 7, 1992 Results Reports]for Air Monitoring of Extended Pilot Vapor Extraction Test(Attachment B) . 1998 Upgrade Activities. During July 1998, the service station was upgraded During the upgrade activities, waste oil overspill containment was installed Cambria inspected native soil exposed in the work areas for evidence of petroleum hydrocarbons and none was observed Soil sampling was not required by San Joaquin County Public Health Department Environmental Health Division and no soil samples were collected for chemical analysis These activities are described in Cambria's 1998 Upgrade Site Inspection Report dated October 19, 1998 Groundwater Monitoring Program. There are currently four groundwater monitoring wells(MW-1 through MW-4) and two vapor extraction wells (VEW-1 and VEW-2) onsite that are sampled annually During the first quarter 2002 sampling event, methyl tertiary butyl ether (MTBE) was detected in wells MW-1 and MW-4 at 0 86 and 14 parts per billion (ppb), respectively TPHg and BTEX were not detected in groundwater from any of the site wells sampled VEW-2 was not sampled first quarter due to insufficient water Historical groundwater data and the first quarter 2002 groundwater contour map are included in Attachment C A monitoring well installed by Exxon (MW-8) is located in the sidewalk along Pershing Avenue adjacent to the subject site (Figure 2) Groundwater concentrations in Exxon's well MW-8 decreased to 215 ppb TPHg and 0 60 ppb benzene during the first quarter 2002 sampling event MTBE was not detected in this well Soil results for the investigations and activities described above are presented in Table 1, and the • sample locations are shown on Figure 2 0837 3