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Interim Investigation Report June 21, 1996 <br /> Stockton, California <br /> Chapin Brothers Automotive <br /> 3.0 VAPOR EXTRACTION/MONITORING WELLS <br /> The monitoring well MW5 was constructed using 2-in inner diameter PVC pipe with <br /> 0 020-in slotted casing between 10 and 30 ft below grade The vapor extraction wells VE-5 and <br /> VE-6 were constructed using 4-in inner diameter PVC pipe with 0 10-in slotted casing between 5 <br /> and 20 ft below grade Details of well construction, development , and sampling methods are <br /> presented in Appendices A and B Schematic well diagrams are presented on the boring logs <br /> (Appendix B - Figures B5 through B7) <br /> 3.1 Groundwater Gradient <br /> Well casing elevations were measured on April 25, 1996, to the nearest 0 01 ft by the <br /> licensed surveyor Underwood and Rosenblum of San Jose, California The relative elevations <br /> reported during previous investigations were confirmed, and the elevation of the new well (MW5) <br /> was determined based on the previously reported elevations of the existing wells The <br /> groundwater gradient was then approximated from calculations made using the surveyed wellhead <br /> elevations and locations in combination with depth to groundwater measurements made on March <br /> 20, 1996 The groundwater elevation data from the site indicate that groundwater flow is <br /> generally N65°W with a gradient of 0 0019 ft/ft The surface, however has a pronounced warp to <br /> the west, where the gradient was more northerly at that time <br /> 1 <br /> 1 i <br /> i <br /> 530-001 - 4 - LusH GEOSCIENCES <br />