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Boyett Petroleum January 15, 2001 <br /> • 4.19 South Main Street, Manteca, California Page 4 <br /> Interim Report of Findings for Lateral <br />' Extent of Groundwater Contamination <br />' 3.1 Drilling <br /> The soil borings were accomplished using a mobile mounted drilling rig employing <br />' the use of a hollow stem flight auger whose outer diameter was no less than S <br /> inches. <br />' All drilling equipment was thoroughly cleaned before drilling began, to prevent the <br /> introduction of contamination from off site, and between borings to prevent cross <br /> contamination. <br /> The borings were logged under the direct supervision of a registered professional <br />' using the Unified Soil Classification System (Appendix Q. The color, texture, <br /> moisture, plasticity (if applicable), consistency of the earth materials, pertinent soil <br /> or bedrock characteristics, and any evidence of contamination was noted. All water- <br /> bearing zones and the depths at which they were encountered are noted on these <br /> logs (Appendix A). <br /> iUpon termination, the borings into the saturated zone were completed as monitoring <br /> wells and backfilled with concrete grout, after a Bentonite seal was placed. The <br /> monitoring wells were of a diameter at least four inches (4") greater than the two <br /> inch(2") diameter of the well casing to be used. <br /> The cuttings from the drilling operation were containerized on-site during drilling <br /> ' for proper disposition. The proper method of disposal are dependent upon results <br /> of laboratory analysis. This disposal will be the responsibility of the client unless <br /> other arrangements have been made. <br /> 3.2 Well Construction <br /> All materials used in well construction were thoroughly cleaned prior to introduction <br /> ' into the boring. A Bentonite, or cement and Bentonite grout, was placed at the <br /> bottom of the boring, as necessary. After the seal was allowed to set long enough <br /> to support the weight of the casing, a two inch(2") diameter well casing (PVC)with <br /> end cap and factory perforations for placement in the saturated zone (taking into <br /> account seasonal variation)was placed in the boring. <br /> The screen and filter pack sizes are noted in the wen construction urawuigs <br /> (Appendix A). The casing and end caps were threaded; no PVC cement was used. <br /> The filter pack extends two (2') above the perforated zone. A Bentonite seal at <br /> ' least three feet (3)thick was placed in the annular space above the filter pack <br />