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Boyett Petroleum April 19, 2000 ' 419 South Main Street, Manteca, California Page 4 • Work Plan for Lateral Extent ' of Groundwater Contamination Borings into the saturated zone will be drilled to a maximum of twenty feet (20') beneath the top of the aquifer being explored. Any perching layers encountered will be investigated to a maximum thickness of five feet (5') and will be backfilled with concrete slurry, after a ' Bentonite seal has been placed. If a deeper aquifer is to be investigated, conductor casings will first be grouted into place to seal off the upper aquifer(s), in series, if necessary, and drilling will proceed through the conductor casing after the grout has been allowed to set properly. If evidence of contamination is noted during the drilling, the drilling will be halted until the responsible professional determined the advisability of deeper drilling. Upon termination, the boring into the saturated zone will be completed as a monitoring well and backfilled with concrete grout, after a Bentonite seal has been placed. The boring for the monitoring well will be of a diameter at least four inches (4") greater than the two inch ' (2") diameter of the well casing to be used. The cuttings from the drilling operation will be containerized on-site during drilling for ' proper disposition. The proper method of disposal will be dependent upon results of laboratory analysis. This disposal will be the responsibility of the client unless other arrangements have been made. 3.2 Well Construction All materials used in well construction will be thoroughly cleaned prior to introduction into the boring. A Bentonite or cement and Bentonite grout will be placed at the bottom of the boring as necessary. After the seal has been allowed to set long enough to support the weight of the casing, a two inch (2") diameter well casing (stainless steal or PVC) with end cap and factory perforations for placement in the saturated zone (taking into account seasonal variation) will be placed in the boring. The screen and filter pack sizes will be as noted in the well construction drawing. The casing and end caps will be threaded or joined ' by stainless steel screws; no PVC cement will be used. The filter pack will extend two feet (2') above the perforated zone. A Bentonite seal two to three feet (2-3') thick will be placed in the annular space above the filter pack followed by a cement grout to the surface. Seal and filter pack elevations may change based on the underlying geology (Appendix Q. 3.3 Well Development and Sampling The well will be developed until the well water appears clear of sediment_ or until an ' appropriate number of well volumes (based on the judgment of the responsible professional) have been evacuated. The water produced during well development will be containerized ' and left on-site in 55-gallon drums of other suitable containers for disposal of hazardous waste if deemed necessary upon receipt of laboratory results. Disposal will be the