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11 � CAMBRIA SITE CONDITIONS Lithology Native sediments underlying the site consist of predominantly silts (ML) and clays(CL) to a maximum depth explored of 51 5 fbg Some nunor silty sand(SM)lenses were also encountered Fill material was also encountered to 13 5 tbg in well boring MW-4, located adjacent to the former UST complex Boring logs are included in Attachment D and geologic cross sections are presented in Attachment E Hydrogeology Depth to groundwater beneath the site has ranged from 13 to 32 fbg In general, the groundwater beneath the site has risen since monitoring began (1996) During the most recent monitoring event(February 2002), the depth to groundwater under the site ranged from 15 to 17 tbg The groundwater flow direction beneath the site ranges from north to northwesterly and away from a hydraulic mound near MW-4, at a gradient ranging from 0 002 to 0 004 Groundwater depth and elevation data and the most recent groundwater contour map are included in Attachment C Hydrocarbon Distribution in Soil. Three soil samples were collected from the waste oil UST excavation during 1987 One of these samples contained 8,230 ppm TPHmo, 298 ppm TPHg, and 0 044 ppm benzene The other two samples did not contain detectable concentrations of TPHmo, TPHg, or benzene, suggesting that impact to soil is localized in this area Soil borings and samples from the former UST area contained TPHg up to 4,300 ppm and 10 ppm benzene,with the maximum concentrations in sample T2-S Soil samples collected from the western and eastern dispenser areas contained 6 7 and 58 ppm TPHg,respectively Benzene was not detected in the dispenser areas Soil data is presented on Table 1 and the sample locations are shown on Figure 2 Hydrocarbon Distribution in Groundwater. During the first quarter 2002 sampling event, MTBE was detected in wells MW-1 and MW-4 at 0 86 and 14 ppb,respectively TPHg and BTEX were not detected in groundwater from any of the site wells sampled VEW-2 was not sampled this quarter due to insufficient water TPHg and BTEX have not been detected in groundwater samples collected from the site wells since August 1999 and MTBE concentrations in all site wells have been below 5 ppb since May 1999 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 isadjacent to the subject site(Figure 2) Groundwater concentrations in Exxon's well MW-8 decreased 0837 4