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V 15 April 2003 AGE-NC Project No. 02-0950 Page 2 of 10 u valley; the site itself is located on unconsolidated and semi-consolidated alluvium, lake,playa and terrace deposits of Quaternary age. 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 20 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 ofEqual Elevation of Groundwater Spring 1999 also published by the San Joaquin County FCD&WCD, the site is in an area where ground water appears to be flowing southwest. 2.2. UNDERGROUND STORAGE TANK REMOVAL It is our understanding that two underground storage tanks (USTs) were removed from the site in March 2002. The USTs were reportedly utilized for the storage and dispensing of gasoline and diesel. Concentrations of total petroleum hydrocarbons quantified as diesel (TPH-d), gasoline `r (TPH-g), volatile aromatics (benzene, toluene, ethyl benzene and xylenes - BTEX) and total lead were detected in soil samples collected from the UST excavation. V 2.3. PREVIOUS SITE INVESTIGATIONS V On 15 and 16 October 2002, AGE advanced soil borings B1 though B3 to a depth of 35 feet bsg at the site. TPH-g was detected in soil samples collected from all three borings at a maximum concentration of 22,000 milligrams per kilogram (mg/kg)(Table 1). TPH-d was detected in soil samples collected from borings B1 and B2 at a maximum concentration of 7,500 mg/kg. BTEX compounds were detected in soil samples collected from all three borings at maximum concentrations of 1.1 mg/kg, 460 mg/kg, 320 mg/kg and 1830 mg/kg, respectively. Lead was detected by EPA Method 6010B in one soil sample collected in boring B2 at a concentration of 59 mg/kg.No additional target analytes were detected at or above laboratory detection limits in the soil samples analyzed. TPH-g was detected in ground water samples collected from each boring at a maximum concentration of 170,000 micrograms per liter(µg/1)(Table 2).TPH-d was detected in ground water samples collected from borings B 1 and B2 at a maximum concentration of 23,000 µg/1. BTEX compounds were detected in ground water samples collected from all three borings at maximum concentrations of 550 gg/l,23,000 gg/1,6,100µg/1 and 33,000µg/1,respectively. 1,2-dichloroethane Advanced GeoEnvi ro n mental,Inc. r