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— - Geological Audit Services, Inc. 1803 W. March Lane, Suite A •Stockton, CA 95207 • (209) 956-0264• FAX (209) 956-0700 V WORK PLAN FOR SITE ASSESSMENT 1014 N. El Dorado Street Stockton, California SITE DESCRIPTION The site is located in a flat light industrial/commercial area of central Stockton (Figure 1 - Location Map, 7. 5 Minute Stockton West Quadrangle, USGS Topographic Map Series, 1987) . A small building and two canopies are present on the property. The site was a gasoline station. The underground storage tank facility apparently consisted of five fuel tanks, one waste oil tank, three fueling islands and their appurtenant piping. Based upon the existing records, all tanks, piping and dispensers have been removed from the site. The property is currently not occupied. The site is underlain by unconsolidated Quaternary alluvial sediment. The upper twenty feet consists of clayey sands to silty sands. Groundwater is estimated at 45-55 feet below surface grade (San Joaquin County Department of Public Works, Flood Control Section, 1990) . PREVIOUS WORK According to records at the San Joaquin County - Environmental Health Division (SJEHD) between three and five underground tanks were removed from the property by an unknown contractor in 1984 (see Figure 2 - Site Plan) . The records do not indicate whether soil samples were collected or analyzed. The excavation was apparently backfilled and covered with asphalt. In February 1988, under the direction of BSK & Associates, one soil boring was drilled to a depth of 26. 5 feet in the southeast portion of the property, where the fuel tanks were located. Six samples were collected from the boring and analyzed for total petroleum hydrocarbons (TPH) and aromatic hydrocarbons (BTE&X) . only one sample (at 5. 5 feet) showed any detectable concentration of hydrocarbon contamination (TPH at 4 ppm) . Another underground storage tank (a 550 gallon waste oil tank) was removed by Seibold Corporation in December of 1990. One soil sample from the fill end of the tank was collected by FGL Laboratory at the time of removal. This sample was tested for TPH-d (EPA method 8015) , BTE&X (EPA 8020) , Chlorinated Hydrocarbons (EPA 8010) , Metals (Cd, Cr III and IV, Pb and Zn) and PCB' s (EPA 8080) . Chromium and Zinc were encountered in the sample, but well below the Total Threshold Limit Concentration (TTLC) . The concentrations of the remaining metals were below the detectable limits. The excavation was then backfilled and covered with asphalt to match existing surface. Environmental Services • Hydrogeology•Geotechnical Services