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PROPOSED CLOSURE PLAN BEACON STATION NO. 502 35 NORTH CHEROKEE LANE LODI, CALIFORNIA ' DELTA PROJECT NO. 40-92-813 1.0 INTRODUCTION ' Delta Environmental Consultants, Inc. (Delta), has been 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 is intended to confirm remediation of petroleum hydrocarbons in the soil beneath the site as indicated by quarterly ground water monitoring, ' and to provide justification for regulatory closure of the site. ' 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 levels 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. Measurements of water levels in the monitoring wells are presented in Table 1, and a summary of laboratory analyses of ground water samples is presented in Table 2. 3.0 PROPOSED CLOSURE PLAN Delta recommends drilling and sampling of three soil borings to a depth of 50 feet below grade to assess the efficiency of vapor extraction, and to confirm that no further remediation is warranted at the site. 1 The soil borings would be located to the west, east and south of the underground fuel storage tank location. One of the soil borings would be drilled at a 35' angle in order to collect soil samples from below the underground fuel storage tanks. The proposed soil boring locations are shown in Figure 3. Soil samples will be collected from each boring at 5-foot vertical intervals and will be field-analyzed for the presence of organic vapors with a photoionization detector (PID). Soil samples collected from depths of 10, 20, 30, 40, 45, and 50 feet below grade will be submitted to a state-certified laboratory for ' RPT049.TA