ARCHIVED REPORTS_VAPOR INTRUSION SURVEY - SOIL GAS SAMPLING REPORT

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' Groundwater Monitoring In accordance with the Central Valley Regional Water Quality Control Board (CVRWQCB) request in their letter dated September 26, 2006, PSC initiated quarterly groundwater ' monitoring at the Site in January 2007. Prior to this, it appears as though MW-1 was sampled once in February 1996 and MW-7S and MW-7D were sampled once in October 1997. There is no record that VE-1 was sampled prior to 2007. ' From January through May 25, 2007, approximately 500 milliliters (mL) of liquid-phase hydrocarbons (LPH) were removed from well VE-1. LPH has not been detected in well VE-1 ' since April 2007. Consequently, VE-1 has been sampled during quarterly groundwater monitoring activities since July 2007. The CVRWQCB requested that well VE-1 be included in all subsequent quarterly monitoring events in a letter dated October 12, 2007. LPH has not been detected in the other wells installed at the Site on behalf of Sara Lee and its predecessors. ' 1.3 Local Geology The Site is located in the San Joaquin Sub-basin of the San Joaquin Valley Groundwater Basin. Shallow deposits in this sub-basin consist of alluvium, riverbank, and flood basin deposits. Sediments encountered in these deposits consist of interbedded sands, silts, and clays of various thicknesses. Soil borings drilled on and in the vicinity of the Site found ' sediments indicative of the sub-basin and are primarily clay, silt, sand, and gravel of varying thicknesses. Sandy gravel fill was encountered in the former UST excavation at the Site to depths of ' approximately 10 to 12 feet bgs. Soil encountered in the 15 borings and wells drilled at the Site in 2007 generally consisted of silt and/or clay with lesser amounts of sand. A silty sand layer measuring approximately 0.5 to 2.5 feet thick was occasionally encountered in the borings between approximately 17.5 and 28 feet. Alternating layers of silt, sandy silt, silty sand, and sand were encountered from 45 feet bgs to ' a total depth of 82.5 feet bgs at boring MW-71). Sandy gravel was encountered in boring MW-71) below 82.5 feet bgs. Layers of interbedded sand and silty sand were encountered at about 45-60 feet bgs, 70-90 feet bgs, and a thin layer around 115-120 feet bgs in the CPT ' investigation performed in April 2008. Based on geologic cross-sections prepared by consultants for the Dolly Madison, Chevron, ' and former Arco sites, the sandy gravel is present beneath the Chevron, and former Arco sites at depths of approximately 60 to 90 feet bgs (Stratus, 2007; BBL, 2006; Delta, 2000). Sand and/or sandy gravel layers have been encountered at depths ranging from 105 to 120 feet bgs ' in borings located at the former Arco and former Texaco sites (Delta, 2000). 1.4 Local Hydrogeology ' Shallow groundwater in the San Joaquin sub-basin is found in un-confined and semi-confined conditions. Shallow groundwater is generally of good quality. However, saltwater intrusion 1 Vapor Intrusion Survey Soil Gas Sampling Report ' Prepared For:Sara Lee Bakery Gmup,Inc. Prepared By:PSC Industrial Outsourcing,LP Sam Lce—Lincoln Street\2009-03_31-Soil Gas Sampling Report.doc March 31,2009 3