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Z Ms. Lori Duncan Page 2 The UST pit was backfilled to grade and the surface repaved. The locations of the former USTs are depicted on Figure 2. Laboratory analytical results are summarized in Table 1. Hydrogeologic Setting The site is located in south central Manteca approximately 1/2 mile north of Highway 120. There are no naturally occurring bodies of surface water in proximity to the site. Surface elevation at the site is approximately thirty five feet above sea level. Based upon published data from the San Joaquin County Flood Control and Water Conservation District (Spring 1997 Groundwater Report), groundwater is expected to be encountered at a depth of approximately 15 to 17 feet below grade in the site vicinity. Groundwater flow is expected to be generally toward the northwest. Historical low groundwater is estimated to have been approximately 30 feet below grade (Fall 1994 Groundwater Report). Soil in the site vicinity is expected to be primarily sandy (USDA, Soil Conservation Service). During the UST removal it was noted that soil at a depth of nine feet was sand. Workplan In order to investigate the lateral and vertical extent of soil contamination resulting from the former USTs and to determine if groundwater has been impacted, Ground Zero proposes drilling and sampling four soil borings at the approximate locations shown on Figure 2. Drilling and Sampling A C-57 licensed drilling company will advance soil borings at the approximate locations shown on Figure 2 using a truck mounted Geoprobe direct push rig. The soil boring located within the former tankpit will be advanced to a depth corresponding to the historic low groundwater depth (approximately 30 feet) to evaluate the vertical limits of contamination. The other borings will be advanced to first encountered groundwater (estimated to occur at approximately 15 feet). Upon completion, the soil borings will be backfilled with cement grout to ground surface. Soil samples will be collected at five foot intervals to total depth for lithologic identification and field screening for contamination. Soil samples will be collected in clear acetate liners with the direct-push drilling equipment. Samples selected for laboratory analysis will be capped, labeled for identification and immediately placed in an ice-chest chilled to 4° C. A groundwater sample will also be collected from the central boring. The groundwater sample will be collected using a discrete sampling device (Hydropunch or equivalent) driven into the water bearing zone. After driving the sampling device to the appropriate depth, the drill rods manteca.eqp\workplan