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Ms. Mary Raygoza October 8, 1990 Page 2 Scope of Work TASK 1 Drill and Sample Soil Boring(s). A soil boring will be drilled near the excavation and within the building, as shown on Figure 1. The boring, TB- 1, will be drilled with a Simco 2400 hollow-stem auger rig. Soil samples will be taken at 5-foot intervals and at significant lithology changes. Samples will be taken in three 6-inch brass tubes from an 18-inch split-spoon sampler. The lower tube from each sample will be labeled, capped, sealed with duct tape, and stored on ice for possible laboratory analysis. The next higher tube will be emptied into a plastic bag, logged geologically and screened in the field for hydrocarbons by sight, odor, and by headspace analysis with an Organic Vapor Analyzer (OVA). The headspace analysis consists of sealing the plastic bag, allowing hydrocarbon vapors that may be present to volatilize for several minutes, then measuring the hydrocarbon concentration with an OVA. Samples with a noticeable odor, or having a headspace concentration of greater than 50 parts per million (ppm) are assumed to contain hydrocarbons. The boring will be advanced until no evidence of hydrocarbons is detected, or the limits of the rig are reached (approximately 50 feet). Ground water in the area is at a depth of approximately 85 feet and is not expected to be encountered. One sample from the interval estimated to contain the highest concentration of hydrocarbons, and one from the bottom of the boring, will be sent to a state-certified laboratory to confirm the headspace analysis and the vertical extent of hydrocarbons within the boring. If no evidence of hydrocarbons is detected in any of the samples from the boring, then only the deepest sample will be submitted for analysis. The. samples will be analyzed for TPHG, TPHD,and BTEX using appropriate sample preparation and analysis methods set forth in the 'Tri-Regional Board Staff Recommendations for Preliminary Underground Tank Investigations". ESE estimates that one 30-foot boring will be sufficient to assess the vertical and lateral extent of hydrocarbons near the excavation. If more or deeper borings are needed, Delta Truck Sales will be informed. It is also assumed that only one sample will be sent for laboratory analysis. TASK 2 Deepen and Enlarge the Excavation. The excavation will be deepened and enlarged (overexcavated) to try to remove the soil containing hydrocarbons, as indicated by Samples #5 and #2 from the January 1989 sampling activities. As the overexcavation proceeds, grab samples of soil will be taken from the `-� excavator bucket and screened by sight, odor, and by headspace analysis for