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Stantec Site History and Previous Investigations Stockton Charter Way Commingled Plume February 15, 2011 activities are summarized in the Touchstone UST Closure Report and Limited Over-excavation Sampling Report dated August 7, 1997. Former Colombo/Toscana Bakery (Sara Lee) Colombo/Toscana owned and operated two 4,000-gallon gasoline UST systems for fleet refueling at the property. The USTs were located west of and adjacent to the warehouse building. The fuel dispenser was located inside the building near the northwestern corner. Environmental investigations have been performed at the property since February 1996 to evaluate the degree and extent of contamination in soil and groundwater. Mr. Edward Overton currently owns the property. In February 1996, SECOR advanced four soil borings (MW-1, VE-1, S13-1, and S13-2). A groundwater monitoring well was installed in MW-1 and a vapor extraction well was installed in VE-1. TPHg and benzene were detected in soil samples collected during the installation activities at concentrations up to 13,000 and 44 mg/kg, respectively. TPHg and benzene were detected in groundwater samples collected from these borings at concentrations up to 190,000 and 22,000 pg/L, respectively. These activities are summarized in the SECOR Summary Report, Site Investigation dated June 11, 1996. In October 1997, SECOR advanced one soil boring (MW-7) through the former UST excavation. A dual-nested groundwater monitoring well (MW-7S and MW-7D) was installed in MW-7. TPHg, benzene, and MTBE were detected in soil samples collected during the installation activities at concentrations up to 390, 2.3, and 0.052 mg/kg, respectively. TPHg, benzene, and MTBE were detected in groundwater samples collected from this boring at concentrations up to 400,000, 19,000, and 120 pg/L, respectively. These activities are summarized in the SECOR Results of Deeper Exploratory Boring and Well Installation and Work Plan to Perform a Cone Penetrometer Testing (CPT) Survey dated November 24, 1997. In December 1997, SECOR advanced three CPT borings (CPT-1 through CPT-3) to further assess the vertical and horizontal extent of petroleum hydrocarbons beneath the property. TPHg was detected in groundwater samples collected from these borings at concentrations up to 17,000 pg/L. These activities are summarized in the SECOR Results of Cone Penetrometer Testing (CPT) Survey dated March 9, 1998. In April 2007, ETIC Engineering, Inc. of Pleasant Hill, California (ETIC) performed a water well survey within 2,000 ft of the property. The Environmental Data Resources (EDR), the California Department of Water Resources (DWR), and Cal Water were contacted to identify water supply wells in the vicinity. EDR identified one public well (W1 — located at V&P Trailer Park; approximately 2,000 ft northeast of the property) within the search radius. DWR had no records for agricultural, domestic, industrial, or municipal water supply wells within the search radius. Cal Water indicated that they did not have a well within the search radius via a telephone call and fax communication. The location of W1 could not be verified during the field visit performed on March 13, 2007. Appendix A- Site History and Previous Investigations.doc 5