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S Ms. Lori Duncan November 18, 1999 Page 2 of 3 SCOPE OF WORK Ground Zero will supervise the drilling and sampling of five soil borings in the vicinity of the former USTs to a depth of approximately 35-40 feet below ground surface (bgs) to investigate the vertical and lateral extent of residual hydrocarbons in the soil. If field evidence (odors, discoloration, field meter readings) indicate that residual contamination is present at the bottom of a given boring, then drilling will continue until no further evidence of impact is present or refusal is encountered. Four borings will be placed in the vicinity of the former gasoline storage tank to assess the vertical and lateral extent of documented soil contamination, and one angle boring will be advanced 20 degrees from vertical beneath the building/waste oil UST to assess the vertical extent of contamination beneath the former waste oil UST. Groundwater reportedly occurs at approximately 130 feet bgs according to maps published by the San Joaquin County Flood Control and Conservation District and is not expected to be impacted. The proposed boring locations are shown on Figure 3. A drilling company licensed in the State of California will advance the borings using a truck mounted Geoprobe® 5400 direct push rig. Soil samples will be collected for logging and identification purposes at 5-foot depth intervals. Samples will be collected using a 1-inch diameter core sampler lined with clear acetate sleeves. Samples collected beneath the waste oil UST will be collected at vertical depths of approximately 15, 20, and 25 feet bgs, which correspond to measurements of approximately 16, 21.3, and 26.6 feet along the axis of the boring, based the equation MD = d/sin(90°a) where: MD = measured depth along boring axis; d = desired vertical depth of sample; a = angle of boring from vertical. To position the 20-foot deep sample (21.3 feet along boring axis) directly below the former UST, the proposed angle boring will penetrate the ground surface approximately 7.3 feet southeast of the center of the former UST, based on the equation HD = MD,cos(90°a) where: HD = horizontal step out distance to begin boring at ground surface; MDC = measured depth along boring axis that corresponds to center line of UST; a = angle of boring from vertical. The portion of each sample to be analyzed will be immediately capped and preserved in an iced cooler at a temperature of approximately 4° Centigrade. No cuttings requiring disposal will be produced using the direct push drilling method. Borings will be backfilled to the ground surface with neat cement grout. Up to three soil samples per boring will be submitted for analysis of petroleum hydrocarbon constituents. Samples collected from the four borings in the vicinity of the former gasoline USTs will be analyzed by a State-certified laboratory for total petroleum hydrocarbons as gasoline (TPHg) using data/groundze/frankstire/wp 1199.doe