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Preliminary Investigation and Evaluation Report SAN JOAQUIN ELECTRIC 525 North Union Street, Stockton, California 1.0. INTRODUCTION In accordance with the request of Mr. Randy Sutphin,Advanced GeoEnvironinental, Inc. (AGE) has prepared this Preliminary Investigation and Evaluation Report for the property located at 525 North Union Street, Stockton, California. The scope of work included the advancement of one soil probe boring and the collection and analysis of soil samples. The location of the site and the immediately surrounding area are illustrated on Figure 1. The structures, former UST and soil probe boring locations are depicted on Figure 2. 2.0. BACKGROUND -� The subject property is located in a commercial area of central Stockton, California,on the southwest corner of North Union Street and Oak Street (Figure 1). Railroad tracks are located west of the site. It is AGE's understanding that one 550-gallon UST was removed from the site on 15 October 1987. The UST was installed in a bunker. The bunker was constructed with three concrete walls and floor while the fourth wall was dirt. A product dispenser was formerly located near the northeast corner of the UST. Total petroleum hydrocarbons quantified as gasoline and motor oil (TPH-g and TPH- mo) were detected in a soil sample collected from the north sidewall of the excavation at concentrations of 30 parts per million (ppm, reported as milligrams per kilogram) and 2,700 ppm, respectively. Benzene, toluene and xylenes were detected in this sample at concentrations of 5 ppm, 0.05 ppm and 8 ppm,respectively. TPH as diesel and kerosine(TPH-d and TPH-k)were not detected in the sample. Site assessment was subsequently required by the PHS-EHD. Based on the San Joaquin County Flood Control and Water Conservation District map titled Lines of Equal Depth to Groundwater - Fall 1998, ground water at the site is estimated to be approximately 45 feet below surface grade (bsg). 3.0. PROCEDURES Field work was performed as proposed in the approved work plan Site Assessment Work Plan dated 12 May 1998 and prepared by AGE in accordance with San Joaquin County Public Health Services - Environmental Health Division (PHS-EHD) and Central Valley Regional Water Quality Control Board (CVRWQCB) guidelines for the investigation of underground storage tank (UST) sites. Advanced GeoEnvlronmental,Inc.