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Ms. Gail Wiggett Project OC42-001.023 <br /> July 10, 1995 <br /> Page 2 <br /> and sealing the borings with grout. An above ground pipeline restricted drill rig access to <br /> P-32. P-32 was sealed in place with grout. <br /> Piezometers P-9 and P-14 were included in the decommissioning because the protective <br /> monuments were no longer in place and there were no surface seals. In addition, the <br /> casing of P-14 was bent and inaccessible for water level measurements. Piezometer P-15 <br /> could not be located and was not decommissioned. <br /> An SJCDEH representative observed decommissioning of piezometers P-18 through P-20, <br /> P-22, P-24, P-25, P-27, P-28, and P-32. <br /> MONITORING WELL DECOMMISSIONING ACTIVITIES <br /> Two 4-inch diameter monitoring wells, PS/MW-3 and PS/MW-13, screened across the <br /> A-zone and into the upper B-zone were decommissioned. The surface seal, filter pack, and <br /> casing were drilled out using 10-inch diameter hollow-stem auger drilling equipment to <br /> depths of approximately 31 feet below ground surface. The borings were sealed with <br /> cement grout containing 5 percent bentonite tremied from the base of the borings to <br /> ground surface. <br /> A representative of the SJCDEH observed decommissioning and grout placement. <br /> MONITORING WELL REPLACEMENT <br /> Monitoring well pair PS/WC-2s,m have been inaccessible for water level measurements <br /> and groundwater sampling since 1993. The wells are scheduled for quarterly groundwater <br /> sampling under the provisions of Monitoring and Reporting Program 93-807. Well <br /> replacement activities were conducted to provide new monitoring points at this location. <br /> The existing well seals, filter packs, and casing were drilled out to depths of 20 and 35 feet <br /> below ground surface for wells PS/WC-2s and PS/WC-2m, respectively, using 8-inch <br /> diameter hollow-stem auger drilling equipment. New 2-inch diameter monitoring wells <br /> were constructed in the respective borings consistent with the completion details of the <br /> damaged monitoring wells. Raised concrete surface pads with heavy duty vault boxes were <br /> installed for well head protection and access during wet season monitoring events. <br /> Construction details are presented on Well Completion Sheets presented in Attachment A. <br /> The replacement well pair was developed in June 1995, using a combination of surging and <br /> bailing techniques. The wells were sampled during the second quarter 1995 groundwater <br /> SACNN�PJM('42�DC420012.3CL-954mp:1 <br />