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I C 2.4 October 2003 Diesel Dispenser Grab Soil Sample Results Geo-Logic did not observe any field evidence of hydrocarbon contamination at the diesel dispenser excavationDiesel . The collected sample contained 140 m /K diesel and 2.4 mg/Kg gasoline, but did ( ) p mg/Kg � l {- not contain BTEX or MTBE (Table 1A). . 2.5 October 2003 Waste Oil Tank Piping Grab Soil Sample Results r Geo-Logic observed no evidence of hydrocarbon contamination in,the WOT piping trench, including the f two WOT soil sample locations. Analytical results of the P1 and P2 samples indicated metals concentrations that appear to be natural background concentrations. The only VOC detected was PCE, in both samples, at trace concentrations of 0A079 and 0.0055 mg/Kg (Table 1 B). T � 3 SITE DESCRIPTION This Stockton Service Center is used for obtaining, storing, and distributing materials and equipment for � the gas and electric operations work crews. Since 1962, the facility has been operating on a twenty-two acre site owned by PG&E. There are office, operations, shops, and fleet services buildings, a warehouse, and the subject fuel facility and WOT. The fuel facility includes two 10,000-gallon underground storage- tanks (USTs)of unleaded gasoline and diesel fuel. ' t}r 4 TOPOGRAPHIC AND GEOLOGIC SETTING ? i The Stockton Service Center is 21 feet above mean sea level (MSL). The topography in the area is gentle. The nearest surface drainage is the Calaveras River, 900 feet north of the fuel facility. A geologic map of the region (Wagner, et. al. 1990) indicates that the Quaternary Modesto Formation underlies the service center. The Modesto Formation is an alluvial.fan deposit that typically consists of I� discontinuous, lenticular clay and silt lenses interbedded with sand',-rich sediments from the Sierra Nevada Mountains. ' Based on the site elevation and topography,groundwater beneath{the site is expected to occur at twenty ' to.thirty feet. I i I V! I 'i y - 402.331.04.30 3 !