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Musco Family Olive Compan6 - 3 - 29 September 2006 <br /> borehole wall to well casing radial thickness of only 1.938 inches. Technically, the <br /> 6-inch diameter auger does not meet the radial thickness standard in Bulletin 74-90. <br /> Furthermore, the possibilities of the drill stem wandering off of vertical is likely thus <br /> reducing the distance between well casing and the borehole wall. Section 9.C. also <br /> states; "additional space shall be provided, where needed, to allow casings to be <br /> properly centralized and spaced and allow the use of a tremie pipe during well <br /> construction (if required), especially for deeper wells." The Discharger has not <br /> proposed centralizers to ensure the well casing is centered within the borehole and the <br /> annular seal is of sufficient depth to warrant grout placement by tremie pipe. <br /> Other problems could result from using smaller diameter auger, specifically bridging of <br /> well construction materials. Bridging of well construction materials could compromise <br /> the effectiveness and integrity of the well, which would require the Discharger to <br /> reconstruct. To reduce or eliminate this potential and to comply with DWR well <br /> standards, the Discharger shall drill the well borings using an 8-inch diameter hollow <br /> stem auger. <br /> • If required, well borings will be abandoned in accordance with San Joaquin County <br /> Environmental Health guidelines and DWR Well Standards Bulletin No. 74-90. <br /> Regional Water Board staff approves the work plan dated 22 September 2006 if the above <br /> conditions are met. If you have questions please call me at (916) 464-4737. <br /> Todd A. Del Frate P.G. <br /> Engineering Geologist <br /> Lower San Joaquin River Watershed <br /> Discharge to Land Unit <br /> cc: Melissa Hall, RWQCB, Sacramento <br /> Robert McClellon, San Joaquin County Environmental Health Department, Stockton <br /> Michael Infurna, San Joaquin County Environmental Health Department, Stockton <br /> Joseph D. Zilles, Kleinfelder, Inc., Stockton <br /> Paula Hansen, Kennedy/Jenks Consultants, San Francisco <br /> TAD/W:\San Joaquin CountyWusw\Letters\WP_response0906 <br />