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25 September 2002 AGE-NC Project No. 99-0581 Page 2 of 5 alluvium, lake, playa and terrace deposits of Quaternary age (California Division of Mines and Geology, 1977).Rocks composing the basement complex of the Province have not been completely defined but are believed to be metamorphic and igneous in origin. The Modesto, Riverbank and Turlock Lake Formations and overlying Recent alluvium are the principal sources of domestic ground water in the 13,500-square mile San Joaquin Valley Ground Water Basin(Basin 5-22).The estimated depth to ground water at the site is approximately 50 to 60 feet below surface grade(bsg)based on information from Lines of Equal Depth of Water Wells Fall 1999,published by the San Joaquin County Flood Control District and Water Conservation District- FCD&WCD. Based on the map titled Lines of Equal Elevation of Groundwater Spring 1999 also published by the San Joaquin County FCD&WCD, the ground water elevation is estimated at approximately 35 feet below surface grade and ground water flow generally toward the east/southeast. However, this may be greatly modified by local recharge and discharge patterns. 2.2. UNDERGROUND STORAGE TANK REMOVAL The following information was obtained from EHD records: One 2,000-gallon unleaded gasoline underground storage tank (UST), one 2,000-gallon regular gasoline UST,one 1000-gallon waste oil UST and one 550-gallon waste oil UST were removed from the site by Precision Industries,Inc. (PH)on 18 March 1987.Following tank removal, a soil sample was collected from the floor of each UST excavation and analyzed at Canonie Environmental, a certified laboratory, for total extractable hydrocarbons (TEH) and benzene, toluene and xylenes (BTX); in addition, the sample from the regular gasoline tank was analyzed for ethylbenzene and total lead and the samples from the waste oil USTs were analyzed for polychlorinated bi-phenols (PCBs) and purgeable hydrocarbons (PH). At that time, the soil samples were not analyzed for the fuel additive methyl tert-butyl ether(MTBE). The laboratory analysis did not detect BTEX,BTX,PCBs and PH in the analyzed samples.TEH was detected at a concentration of 7.3 mg/kg (unleaded gasoline UST) and total lead was detected at a concentration of 9.1 mg/kg(regular gasoline UST). Based upon results of the soil sample analysis, the site was closed by the EHD, with a No Further Action(NFA) letter dated 02 March 1993. 2.3. PREVIOUS SITE ASSESSMENTS An AGE-prepared Phase I Site Assessment,dated 31 December 1999,identified: 1)four former UST locations,2)spray-paint booth,paint storage and solvent recycling areas,3)multiple hydraulic lifts, Advanced GeoEnvironmental,Inc.