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SUBSURFACE INVESTIGATION REPORT BEACON STATION NO. 502 35 NORTH CHEROKEE LANE LODI, CALIFORNIA DELTA PROJECT NO. 40-92-813 1 1.0 INTRODUCTION ' Delta Environmental Consultants, Inc. (Delta), was authorized by Ultramar Inc. (Ultramar) to conduct an investigation of soil conditions at Beacon Station No. 502, located at 35 North Cherokee Lane, Lodi, San Joaquin County, California (Figure 1). The investigation was intended to confirm remediation of petroleum hydrocarbons in the soil beneath the site, and was performed in accordance with the ' Proposed Closure Plan, dated January 8, 1993, and prepared by Delta. This report presents the results of our findings. 2.0 SITE BACKGROUND INFORMATION The presence of petroleum hydrocarbons in soil beneath the site was detected during lining of underground fuel storage tanks in 1987. Since that time, investigative activities at the site have included the installation of five ground water monitoring wells, measurement of water table elevations in the wells to determine ground water flow direction, and sampling of the wells to evaluate ground water quality. Remedial activities have included the installation of a soil vapor extraction system, which has been in operation at the site since 1989. The system applies a vacuum to two of the ground water monitoring wells and four vapor extraction wells: Site facilities are illustrated in Figure 2. ' 3.0 FIELD INVESTIGATION On April 29, 1993, three soil borings were advanced to a depth of 50 feet below grade in the vicinity of the underground fuel storage tank location. Soil boring SB-1 was drilled at an angle of 35° from vertical ' in order to collect soil samples from below the underground fuel storage tanks. Soil borings SB-2 and SB-3 were drilled adjacent to the underground fuel storage tank location to the south and north, ' respectively. Methods used to drill and sample the soil borings are described in Appendix A. Locations of the soil borings are shown in Figure 2. Soil samples were collected from each boring at 5-foot vertical intervals and were field-analyzed for the presence of organic vapors with a photoionization detector (PID). Native soils encountered were } generally sand or silty sand from the surface to depths of 14 to 22 feet, silt, sandy clay, or clayey sand RPT 103.S]H r