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+.. GeofoBicaC?echnics inc. Page 6 City of Escalon Project No. 750.3 { October 31,2000 4.3 Confirmation Testing A series of confirmation tests will be performed at the end of the remediation to evaluate the overall effectiveness of the site cleanup. These tests include the following, which are discussed in the sections below. • soil vapor • soil samples • groundwater Geological Technics Inc. acknowledges that any analytical results are valid only for the point +r that the sample was collected. However, through interpolation, discrete sample data are .. } routinely used to characterize those areas outside the immediate sampling area. These .techniques, which depend entirely on representative sampling, allow information from a discrete sample to be projected over a larger area than was actually tested. Therefore, the confirmation analytical results, VETS influent data, and quarterly groundwater analytical data, will be used for site closure. 4.3.1. Soil Vapor Two types of soil vapor tests will be performed. The steady state tests will be performed during operation of the VETS and the spike test will be performed near the completion of the �. remedial program. Steady State Once the VETS is operational, the influent soil vapor from each extraction well will be analyzed for TPH-G & BTEX once a month. This data will be used to optimize the extraction process (draw soil vapor from the areas with the highest hydrocarbon content and to estimate rates of contaminant removal). Once the asymptotic plateau has been achieved +-� and influent levels are relatively low, the system is ready for conducting a spike test. The point at which this event may take place will be determined by the safe in-situ levels determined by the regulatory agencies. L Spike Test Conducting a spike test can provide information useful in determining when the remediation has accomplished its goal. The spike test is designed to detect minute concentrations of remnant volatile organic compounds that might not be detected during steady state testing_ The advantage of the spike test is that it is able to test areas that may have been isolated by the development of preferential airflow pathways. Closely monitoring and optimizing the i• airflow during remedial operations can reduce the development of these zones. 4.3.2 Soil Samples A confirmation soil boring will be drilled near each point of release to confirm that the remediation has been successful. An addendum to the RAP will be submitted to the DER that will clearly state the sample collection-testing plan. The plan will include the following: • Soil samples will be collected and analyzed from each of the soil types and from the soil that once contained significant levels of TPH-G, BTEX, and the OhCs. • Confirmation borings will extend to the capillary fringe. A soil sample from the capillary fringe would also be collected.