SITE INFORMATION AND CORRESPONDENCE

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` PG&E General Construction Yard inch Camp - 3 - 28 February 2011 r./ remaining in place at depth greater than 11 feet bgs do not pose a threat to human health or the environment. Soil concentrations in samples from the floor of the excavation at 11 feet bgs and from the western sidewall contained petroleum hydrocarbons above the ESLs. PG&E used VLEACH to model the vertical migration of petroleum hydrocarbons in soil to groundwater. PG&E concluded that (1) the maximum concentrations in groundwater occurred within the first year of the release and (2) at 10 years after release, concentrations would be below water quality objectives (WQOs). Figure 3 shows the excavation area and sample locations, and the confirmation soil data are in Table 3. GROUNDWATER INVESTIGATION ACTIVITIES In May 2006, PG&E sampled the onsite domestic well that supplied water for the facility. The only detection was 2,2-dichloropropane at 1 .3 micrograms per liter (pg/L). Historically, the well was used for the restroom facilities and for general commercial use. Potable drinking water is purchased from a drinking water provider. In June 2009, PG&E properly abandoned the onsite domestic well. In April 2007, PG&E drilled five soil borings to determine the lateral extent of petroleum pollution in groundwater at the Site. PG&E collected grab groundwater samples at about 26 feet bgs from each of the soil borings. No petroleum hydrocarbons were detected in the grab samples collected from the borings. In May 2007, PG&E installed three monitoring wells at the Site. As shown on Figure 4, MW-1 is within the former excavation area, MW-2 is east of the former heavy equipment area, and MW-3 is north of the equipment area. All three wells were screened from 19 to 34 feet bgs. Depth to water is about 28 feet bgs. In 2007, MW-1 contained the maximum concentrations of TPHd and TPHg at 850 pg/L and 580 pg/L, respectively. No petroleum hydrocarbons were detected in MW-2 or MW-3. Table 4 presents the groundwater data. PG&E sampled the monitoring wells in November 2007, February 2008, May 2008, and August 2008. As shown in Table 4, TPHd was the only compound detected during this time period at a maximum concentration of 150 pg/L in MW-1 in February 2008. In July 2009, PG&E properly abandoned all Site monitoring wells in accordance with San Joaquin County Environmental Health Department (SJEHD) requirements. SENSITIVE RECEPTORS In 2005, PG&E conducted a sensitive receptor survey and determined that three wells are located within one-quarter mile of the Site. The first well is about 530 feet northwest of the Site and is 236 feet deep. The second well is about 1 ,200 feet northwest of the Site and supplies a Fresno Truck Lines facility. The Fresno Truck Lines well has a history of coliform contamination violations, which resulted in enforcement actions against Fresno Truck Lines by San Joaquin County. These violations are unrelated to the Site. PG&E later located the third well when it observed a pressure tank, presumably connected to a water supply well, at the property immediately adjacent to the Site to the northwest. In July 2009, PG&E sampled the domestic well at the adjacent site, and no petroleum hydrocarbons were detected above the laboratory detection limits.