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FIRESTONE Service Center 400 North El Dorado Street, Stockton, CaLforma October 6, 1993 Site Assessment Work Plan-2072,01 Page 6 of 7 4.6 Soil Analyses Soil samples collected from each boring (estimated at two) will be analyzed within allowable holding times by a certified laboratory for concentrations of • Oil and Grease (O&G) by EPA Method 5520 E&F • TPH Gasoline by the CA Department of Health Services (DOHS) Method • BTEX by EPA Method 8020 These tests will be performed in accordance with protocols prescribed in SW-846 and EPA 600/4-79-020 manuals The analyses above are included in the recommended EPA Methods (for investigating used motor oil and gasoline contamination) as specified by State of California, Central Valley Regional Water Quality Control Board guidelines Several analyses, including TPH diesel, chlorinated hydrocarbons, and metals, have been omitted from the proposed analytical series due to the demonstrated absence of these constituents in previous testing. As stated in Section 4 5, soil samples will represent the soil zones exhibiting maximum PID measurements and/or physical evidence of contamination, and the boring termination depth. In lieu of detectable OVA-PID readings, the most permeable material within the appropriate depth range will be sampled in addition to the boring termination depth Appropriate chain-of-custody documentation will be maintained for all samples transported to, and evaluated by, the analytical laboratory 4.7 Vapor Extraction Well Construction Following soil sample collection, the central soil boring (through the former pit) will be converted to a vapor extraction well. The well will initially be used for a one-day vapor extraction pilot study performed immediately after completion of drilling Based on the pilot study results, the well may be utilized for long-term vapor extraction remediation of site contamination The well will be constructed of 4-inch diameter PVC casing The well screen will be 10- feet in length, with No 10 (0 010-inch) machine slotting The filter pack will consist of standard pea gravel The remaining annular space above the screened zone will be filled entirely with a bentonite grout slurry The well will be finished with concrete slurry and a water-tight flush-mount metal surface cover Specific construction details and dimensions are illustrated on the well construction diagram (Figure 3) RYAN-MURPHY, INCORPORA IFA Denver ' Envhvnmental Contraction Management I" Angeles