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s The soil samples were analyzed for Total Petroleum Hydrocarbons as diesel,benzene,toluene. ethylbenzene, and xylene(BTEX), and MTBE by USEPA Test Methods 8015M and 8020. II Analytical laboratory results are presented in Appendix 3. The results are summarized in Table 1 and plotted on Figure 6. Upgradient suggested the field observations made during drilling(i.e. hydrocarbons present only at 15 and 20 feet bgs in soil boring B1)were valid when compared with analytical laboratory results. No MTBE was reportedly detected in either of these samples. Diesel-range hydrocarbons were detected in the water grab sample from soil boring B3 at a concentration of 1700 µ1l. The ` source of this diesel fuel was most likely from fueling operations spillage. Upgradient(1999)concluded the following from the subsurface investigation: (1). Drilling in and around the UST excavation indicate that fuel leakage from the fueling facility was limited to the fueling piping immediately around the excavation. The boring through the excavation.(B 1)indicated that diesel penetrated less than 10 feet below the former excavation floor,to a maximum depth of 20 to 25 feet bgs. Soil borings within 5 i feet of the lateral margins of the.excavation reportedly encountered no contaminated soil whatsoever. This indicated that lateral leakage from the UST or dispenser did not occur to any appreciable extent.Upgradient reported that the depth to groundwater in the Stockton area in general was generally near its historically highest level (1999), and was reported to be between 40 and 45 feet bgs at a site less than 2000 feet to the north. Based on long-term groundwater measurements by the Flood Control Section of the San Joaquin County Public Works Department,Upgradient concluded that it was unlikely that groundwater had been shallower than 35 feet at the site. Upgradient concluded that it was therefore not likely that the saturated zone had been impacted by petroleum hydrocarbons. MainlDhEnvironmentaRl STE\WorkplanSWorkplan l 1192007.wpd 9