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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 for well installation will be conducted using a truck - mounted drill rig and a continuous -flight <br />hollow -stem auger. The total well depth for 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 for 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 monitoring 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 or 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 for 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: \ Data \GEN \FS -P•T\ 22421 \Permnnng \Stipulation Response \ Groundwater Sampling Plan \Condition 1 Groundwater Sampling Plan 3 .24_03.doc <br />6 <br />