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139 South Center Street, Stockton, California January 25, 1993 Chevron U.S.A. Products Company Page 4 grade. Samples were collected using a 2.5 -inch outside diameter (O.D.) split -spoon sampler, lined with three 2 -inch -diameter by 6-inch4ong brass sample tubes. The sampler was driven 18 inches ahead of the augers at each sample point. One sample from every five-foot interval was sealed with aluminum foil, capped, taped, labeled, placed on ice in an insulated container and delivered under Chain -of -Custody to Superior Precision Analytical Laboratory, a State of California -certified laboratory (Appendix D). Groundwater Technology Standard Operating Procedures (SOP's) for soil sampling are presented in Appendix E. Three soil samples from the soil boring were selected for analysis. Each sample was analyzed for benzene, toluene, ethylbenzene and xylenes (BTEX), and total petroleum hydrocarbons -as -gasoline (TPH-G) by Environmental Protection Agency (EPA) -approved methods 5030/8020/8015, and total lead by Method 6010 (sample MW5-45 only). 3.6 Monitoring Well Installation Upon drilling completion, a monitoring well was installed within the boring (Figure 2). The monitoring well was constructed of 2 -inch diameter, schedule 40 PVC casing with flush threads, and 0.020 -inch - slot well screen. The well screen was installed from a maximum depth of 60 feet up to a depth of 35 feet below grade. A sand filter was placed around the well screen to a height of approximately 2 feet above the top of the screen. The well was completed with a bentonite and neat -cement seal, to grade, and protected by a locking cap and a traffic -rated street box with a water -tight bolted lid. Well construction details are presented in the drill logs (Appendix B). The well head was then surveyed for vertical control using established wellhead surveys as datum points (Appendix C). 3.7 Monitoring Well Development Upon completion, the new monitoring well was developed to remove fine-grained sediments from the well and filter pack. Approximately eight well volumes were extracted, using surge and bailing methods. This technique insures an even sand filter pack, removes fines, and rehabilitates the borehole sides. The fines are drawn from the well by the bailer until the well water is visibly clear. Purge water generated during the development process was stored in a DOT -approved purge water trailer and transported to the Chevron refinery in Richmond, California for recycling. '14 GROUNDWATER TECHNOLOGY