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CONESTOGA-ROVERS &ASSOCIATES table at the site following site upgrades in 1990. Based on this, only soil samples collected after 1990 are considered in the following summary. TPHg was detected in only 1 soil sample collected during dispenser upgrades during 2004 at a concentration of 14 mg/Kg. Up to 3,000 mg/Kg TPH as diesel (TPHd) was detected in 5 soil samples collected during dispenser upgrades. None of the TPHg or TPHd detected matched the laboratory standard. TPHg concentrations not matching the laboratory standard detected in soil samples collected in 1989 at the site (borings SB-1, SB-4, and SB-10) were identified as Stoddard solvent or paint thinner. BTEX was not detected in any of the soil samples collected during the 2004 dispenser upgrades. Tertiary butyl alcohol (TBA) was detected at concentrations up to 0.020 mg/Kg in 3 soil samples collected beneath the dispensers. No other fuel oxygenates (MTBE, diisopropyl ether, ethyl tertiary butyl ether, tertiary amyl methyl ether) were detected. Hydrocarbon Distribution in Groundwater: Historical groundwater data and the most recent groundwater contour map are included in Attachment A. Grab groundwater analytical results from boring CPT-1 are summarized in Table 3. TPHg, TPHd, and BTEX concentrations in wells MW-lA through MW-3A have been near or below method detection limits since monitoring began. TPHg, TPHd, and BTEX have been near or below method detection limits in backfill well BF-1 since at least 2001. Maximum MTBE concentrations have historically been detected in backfill well BF-1 and in monitoring well MW-1A, located northeast of the former USTs. MTBE concentrations are defined vertically by groundwater samples collected from the abandoned water supply well (RW)located onsite. MTBE concentrations have shown a decreasing concentration trend since the initiation of periodic GWE during 2000_ MTBE concentrations in wells MW-2A and MW-3A have been near or below method detection limits since at least 2002. During the first quarter 2007, well MW-1A contained 6.10 pg/L of MTBE. A work plan to investigation the lateral extent of MTBE in groundwater northeast of the site was submitted to the SJCEHD during April 2001. Subsequently,the City of Tracy refused to grant an encroachment permit to investigate within Tracy Boulevard, and offsite investigation could not be completed. A former Unocal Gas Station is located across Tracy Boulevard, northeast of the site, so investigation beyond Tracy Boulevard would be impractical. Additionally, at this time, periodic GWE was proving to be an effective interim remedial approach and MTBE concentrations declined to levels where additional investigation was no longer warranted. 0813 5 Worldwide Engineering,Environmental,Construction,and IT Services