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-- PROPOSED WORK PLAN FOR PRETANK CLOSURE SITE ASSESSMENT Shell Service Station 3725 Tracy Boulevard, Tracy California Delta Project No. 40-0-012 Pale 7 .1 Exploratory Soit Borings A total of ten soil borings will be advanced within the property boundaries of the site (Figure 2). Four soil borings will be advanced adjacent to the existing underground storage tank location. Four soil borings will be advanced in the vicinity of the proposed new tank location, and two other soil borings will be located adjacent to the dispensing line locations. All soil borings will be advanced using 7.5- or 8-inch-diameter hollow-stem augers. Samples will be collected with a California modified split-spoon sampler. Appendix C describes the drilling and V sampling techniques to be used. Soil samples will be collected at vertical intervals of 5.0 feet. Soils - will be screened with a PID as described in Appendix C to determine organic vapor content. Borings will be advanced to a minimum depth of 20 feet, or until soil screening indicates three consecutive LI soil samples contain nondetectable levels of organic vapors. A soil sample containing organic vapor levels comparable to background levels will be considered to contain nondetectable levels of organic vapors. A sample will be submitted for laboratory analysis to verify the field determination. 3.2 Soil SAmiple Collection and Scrgening L' A California modified split-barrel sampler will be used to extract the soil samples from the soil borings. Three 6-inch brass tubes will be inserted into the California sampler to retain the soil w� sample. Upon retrieval, one brass tube will be capped, packaged, and placed in an ice chest at 4°C for shipment to the laboratory. The soils in the second brass tube will be extracted and placed in a t sealed jar until completion of the drilling activities. The samples placed in jars will be brought to !� room temperature, and the headspace of each jar will be screened for total organic vapors utilizing a portable photoionization detector equipped with a 10.2 eV lamp calibrated to benzene for direct t reading in parts per million. Refer to Appendix C for sampling and screening methods. 3.3 Chemical Analysis Based on results of soil sample screening, soil samples will be selected for chemical analysis. Soil samples will be analyzed for TPH by EPA Method 8015. Those samples with TPH concentrations exceeding 100 ppm will be analyzed for BTEX by EPA Method 8020. 4.0 SCHEDULE Delta will proceed with the work outlined in this work plan as soon as approval is obtained. A drill crew will be mobilized to drill the proposed borings within 2 weeks of approval of this plan. Laboratory analysis of soil samples generally requires 3 weeks. A summary report of our results will be prepared within 3 weeks after laboratory results are received. 1 r