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. 45 E Harding Way, Stockton, California March 14, 1994 Chevron USA Products Company Page 5 induction and ground penetrating radar to determine the presence of other tanks, d any The results of the geophysical survey are currently being prepared by Spectrum Environmental Services, Inc 33 Soil Sampling During drilling, soil samples were collected at 5-foot Intervals, beginning at approximately 5 feet below grade to the bottom of each boring Samples were collected using a 2 5-inch O D split-spoon sampler, limed with three 2-inch-diameter by 6-inch-long brass sample tubes The sampler was driven 18 inches ahead of the augers at each sample point Soil samples were field screened for hydrocarbon vapors using a photo-ionization detector (PID) One sample from each 5-foot interval was sealed with aluminum foil, capped, taped, labeled, placed on ice in an insulated container and delivered under chain-of-custody manifest to Superior Precision Analytical Laboratory in San Francisco, California The field geologist maintained a complete log of the materials encountered during drilling using the Unified Soil Classification System (Appendix B) Thirty of the 54 sod samples collected from the soil bonngs were selected for analysis Each sample was analyzed for benzene, toluene, ethylbenzene and xylenes (BTEX), and TPH-G by Environmental Protection Agency (EPA) methods 5030/8020/modified 8015 34 Groundwater Monitoring Well lnstallation/Surveying/Development I Monitoring wells MW-2R and MW-14 were installed at the locations shown on Figure 2 (Appendix B) The monitoring wells were constructed of 2-inch-diameter, schedule 40 PVC casing with flush threads, and 0 020-inch-slot well screen Well screen for both wells was installed from 40 to 65 feet below grade The well annulus was filled with a sand filter pack from the Bottom to one foot above the well screen and a bentonite/portland cement grout to one foot below grade The wells were finished to grade with a traffic-rated, watertight street box set in concrete The wells were secured with a locking, expandable well cap Well construction details are presented on the drill logs attached in Appendix B Following installation, the new wells were surveyed for horizontal position relative to the existing well network and elevation relative to mean sea level datum (Appendix C) On January 16, 1994, MW-2R and MW-14 were developed by surging and bailing to remove fine-grained sediments from the well and filter pack Approximately three well volumes were extracted from each well to remove fine-grain sediment, and to insure an even sand filter pack Water was removed from the well GROUNDWATER 48955uM RPT TECHNOLOGY