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Boyett Petroleum May 18, 2000 419 South Main Street, Manteca, California Page 4 Work Plan for Lateral Extent of Groun(lwater Contamination (Ad(lendum) The borings will be logged under the direct supervision of a registered professional using the Unified Soil Classification System (Figure 4). The color, texture, moisture, plasticity (if applicable), consistency of the earth materials, pertinent soil or bedrock characteristics, and any evidence of contamination will be noted. All water-bearing zones and the depths at which they were encountered will be noted on these logs (Appendix B). All borings will be drilled in such a manner as to prevent cross contamination between strata. Exploratory soil borings within the unsaturated zone will be backfilled with cement and three percent (3%) Bentonite mixture. 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