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SECTION 4 <br />MONITORING WELL INSTALLATION PROCEDURE <br />The Dakota aquifer water supply well (DW-1) is an existing well available for sampling. Contour <br />Consulting Engineering, LLC (Contour) will install monitoring wells MW-001A, MW-002, MW-003, <br />and MW-004 once approval for the location of the wells is granted by DMG. Contour will obtain <br />monitoring well permits from the State Engineer and have utilities located prior to installing the <br />wells. <br />Drilling fox well installation will be conducted using atruck-mounted drill rig and acontinuous-flight <br />hollow-stem auger. The total well depth fox the alluvial wells will be determined by the top of <br />bedrock and is not expected to exceed 20 feet. The alluvial wells will be screened across the alluvial <br />aquifer. Depth to screen will be based on measurements of static water level in the aquifer. The <br />well depth fox MW-001A is not expected to exceed 60 feet, based on depth to the Codell sandstone <br />for MW-001. Wells in the Codell sandstone will be screened from the top of the Codell sandstone <br />to total depth. Each boring will be converted to permanent groundwater motutoring wells using a <br />2-inch diameter schedule-40 flush-joint PVC blank casing and slotted mill-casing (0.010-inch slots). <br />The annular space will be backfilled with 10-20 mesh silica sand to a depth two feet above the <br />perforated interval. A two-foot bentonite seal will be placed above the filter pack. The remaining <br />annular space will be filled with cement grout Drill cuttings from well installation, logged in <br />accordance with applicable AGI ox ASTM standards by a professional geologist or geotechnical <br />engineer, will be thin spread on site. Produced water will be discharged and allowed to infiltrate near <br />the wellhead. The wellhead will be completed using an aboveground steel protective casing with <br />locking cover. Three bollards, extending a minimum of four feet aboveground, will provide <br />additional protection. The bollards will be painted yellow or orange fox maximum visibility. <br />Subsequent to installation, the wells will be developed by purging water. The locations of each <br />wellhead will be surveyed from an established control point. The height of each wellhead above the <br />ground surface will be measured. <br />P:\Dau\GEN\F-S-P--f~22421\Pem~iiting\Sripulxnon Response\Groundwain Sampling Plm\Condiuon I Gmundwam Sampling Plan 3~4_03.doc <br />