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bw bw Work Plan for Temporary Soil Vapor Probes Boyett Petroleum-Manteca June 17, 2008 419 S. Main Street, Manteca, California The presence of petroleum hydrocarbon impacted groundwater has been reported in "grab" groundwater samples collected from soil borings advanced at the Site (CPT-3 through CPT-6 and HP-1 through HP-9). MTBE was reported at a maximum concentration of 12,000 gg/L in boring CPT-4 at 22 feet bgs (October 2003). During the most recent "grab" groundwater 6W sampling at the Site (August 2006) MTBE was reported at a maximum concentration of 65 µg/L in boring HP-9 at 30 feet bgs. The source of MTBE in groundwater in the deep soil `" horizon is likely the downward vertical migration of MTBE from the shallow aquifer to the deep aquifer in monitoring well MW-1. Monitoring well MW-1 was installed in 1999 by WW WHF. The screen in MW-1 penetrated the clay to silty clay horizon that separates the shallow and deep soil horizons. Monitoring well MW-1 was properly destroyed in October 2003. In a report dated October 7, 2005, Condor calculated the approximate mass of dissolved MTBE in the groundwater under the Site as being 0.03 pounds as of June 2005. 1.4 Summary of Sensitive Receptors A Sensitive Receptor Survey (SRS) was conducted at the Site by WHF during March through May of 2000. The SRS was conducted to find any sensitive receptors within a 2,000-foot radius of the Site. WHF conducted interviews coupled with physical Site inspection and contacted the following agencies, the City of Manteca, San Joaquin County Public Health Services and the State of California Department of Water Resources (DWR), in order to identify all sensitive receptors within the survey area. The closest well found was a public water well located at 331 Jessie Road, approximately 1,000 feet southwest (down-gradient) of the Site and Manteca High School located approximately 2,000 feet northwest (down- gradient) of the Site. In November of 2002, Condor Earth Technologies, Inc. (Condor) conducted a SRS to identify all sensitive receptors within a 2,000-foot radius of the Site. This SRS included r reviewing DWR well logs, contacting City of Manteca Public Works (CMPW) and an area reconnaissance conducted on foot (500-foot radius) and by automobile (2,000-foot radius). The closest well found was a public water well approximately 1,500 feet west (down- gradient) of the Site located at 331 Jessie Road but during the Site reconnaissance this well was found at 323 Jessie Road. The CMPW informed Condor this well tested negative for MTBE in 2002. A drinking water well was found approximately 1,800 feet northeast (up- gradient) of the Site located at Manteca High School. Two schools were identified within the 6W Page 3 of 8 Closure Solutions,Inc v