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There are a total of 8 A Zone, 7 B Zone, and 6 C Zone wells that have <br /> been proposed for installation at SHAD. ESEs drilling contractor, North <br /> Valley Drilling, Inc. , will apply for the necessary permit from San <br /> Joaquin Local Health District to expedite the Monitor Well Installation <br /> Program• <br /> All monitor wells will be installed in accordance to the United States <br /> Army Toxic and Hazardous Materials Agencies (USATHAMA) Geotechnical <br /> Requirements for Drilling, Monitor Wells, Data Acquisition, and Reports <br /> (March 1987) . The well boreholes will be drilled with a rotary drilling <br /> rig and a monitor well will be constructed, screening the upper 10 ft of <br /> the aquifer. The well material will be 4-inch O.D. Schedule 40 Polyvinyl <br /> (PVC) . The typical well construction used at SHAD is shown in Figure <br /> 4.2.2-1. Threaded blank PVC will be used except for the 10 ft section of <br /> screened PVC with 0.010-inch slots that will screen the upper portion of <br /> the aquifer being monitored. A sand filter pack will extend 5 ft above <br /> the screen and a 5 ft thick bentonite seal will be placed above the <br /> filter pack to prevent migration of water from any overlying aquifer. <br /> After the bentonite seal has been allowed to swell and set, the annular <br /> space will be grouted to the surface in the presence of a San Joaquin <br /> Local Health District inspector. The grout will consist of a neat cement <br /> and powdered bentonite mixture with a 20 to 1 ratio, respectively. The <br /> construction details of each completed well will be provided to the San <br /> Joaquin Local Health District inspector. Each monitor well will have a <br /> locked steel protective casing to prevent any tampering of the well or <br /> well water. <br /> Drilling Water and Cuttings <br /> All drill cuttings and water will be contained: the cuttings will be <br /> placed on visqueen in the designated South Balloon area at SHAD. The <br /> cuttings from each well cluster will be labeled with the well number. <br /> All drilling and well development/purge water will be entered into the <br /> South Balloon Water Treatment Facility for treatment. <br /> PrPrmutions to P pt nt Potential Cros rontamination <br /> All drilling and sampling equipment will be steam cleaned in a designated <br />