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Geosyntec <br /> C011Stt11MUS <br /> FIELD ACTIVITIES <br /> 5.1 Well Installation <br /> The extraction wells will be drilled and installed by a C-57 licensed well drilling contractor using <br /> a mud rotary drilling rig under supervision of a Geosyntec field staff working under the direction <br /> of a California licensed Professional Geologist. The proposed well construction diagrams for <br /> EW-18A, EW-18B, and EW-19 are shown in Figures 4, 5, and 6, respectively. The proposed <br /> well construction details are included in Table 1. Based on the anticipated flowrates and target <br /> well depths, it is anticipated that up to 6-inch-diameter pumps will be needed to achieve the <br /> desired capture. Therefore, the extraction wells were designed with 10-inch nominal diameter <br /> casing. <br /> 5.1.1 Drilling and Geophysical Logging <br /> At EW-18A, EW-18B, and EW-19,the borings will be drilled to approximately 100, 190, and <br /> 275 feet bgs, respectively. The total depth of the borings may be adjusted in the field based on <br /> field observations, such as the depth at which Corcoran Clay is encountered. <br /> Downhole geophysical logs will be conducted in the boreholes to the total boring depths. The <br /> suite of geophysical logs will include: natural gamma; spontaneous potential (SP), 16-inch <br /> normal resistivity, 64-inch normal resistivity, and lateralog-3. The geophysical logging will be <br /> used to determine the final screen intervals for EW-18A, EW-18B, and EW-19. The depth of the <br /> screen interval may be adjusted and blank casing may be installed within sections of the target <br /> screen intervals across fine grained clay and silt layers. The CVRWQCB and County will be <br /> notified of changes made to the proposed screened interval and well depth based on the <br /> geophysical logging of the borehole. <br /> 5.1.2 Extraction Well Installation <br /> An approximately 16-inch nominal diameter boring will be drilled to the target well depth at <br /> each well location using the mud rotary method. The extraction well casings and screens will <br /> consist of 10-inch nominal diameter Type 304 stainless steel. The wells will be fitted below the <br /> screened interval with a 10-inch nominal diameter, welded or flush-threaded bottom plug. <br /> Centralizers will be placed along the blank casing at minimum intervals of 40 feet to keep the <br /> well centered in the boring during installation. The well screens will be constructed of wire wrap <br /> screen. Based on the sieve sample results collected at the nearby PW43 boring, the screens will <br /> be constructed with 0.055 slot and 8x16 filter pack sand (Appendix B). <br /> The filter pack and seal materials will be installed via tremie pipe. The filter pack intervals will <br /> be installed from the bottom of the borehole to a depth of approximately 10 feet above the top of <br /> the screen interval. The volume of filter pack will be monitored during installation by field staff <br /> to confirm that the volume of material used is consistent with the volume of the borehole. <br /> Surging of the extraction wells during installation of the filter pack will be performed to ensure <br /> proper settling and to avoid annular void spaces in the filter pack surrounding the well <br /> Extraction Well Installation Work Plan 5 November 30,2018 <br />