2003-03-03_HYDROLOGY - M2002004 - Laserfiche WebLink

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SECTION 4 MONITORING WELL INSTALLATION PROCEDURE The Dakota aquifer water supply well (DW -1) is an existing well available for sampling. Contour Consulting Engineering, LLC (Contour) will install monitoring wells MW -001A, MW -002, and MW- 003 once approval for the location of the wells is granted by DMG. Contour will obtain monitoring well permits from the State Engineer and have utilities located prior to installing the wells. Drilling for well installation will be conducted using a truck- mounted drill rig and a continuous -flight hollow -stem auger. The total well depth for the alluvial wells will be determined by the top of e oc expected to exceed 20 feet. The well depth for MW -001A is not expected to exceed 60 feet, based on depth to the Codell sandstone for MW -001. Each boring will be converted to permanent groundwater monitoring wells using a 2 -inch diameter schedule -40 flush -joint PVC blank casing and slotted mill- casing (0.010 -inch slots). The annular space will be backfilled with 10- 20 mesh silica sand to a depth two feet above the perforated interval. A two -foot bentonite seal will be placed above the filter pack. The remaining annular space will be filled with cement grout. Drill cuttings from well installation, logged in accordance with applicable AGI or ASTM standards by a professional geologist or geotechnical engineer, will be thin spread on site. Produced water will be discharged and allowed to infiltrate near the wellhead. The wellhead will be completed using a metal protective casing with locking cover. Subsequent to installation, the wells will be developed by purging water. The locations of each wellhead will be surveyed from an established control point. The height of each wellhead above the ground surface will be measured. A-4 f P:\ Data\ GEN\ F -S -P -T \22421 \Permnnng \Snpulanon Response \Groundwater Sampling Plan \Condmon 1 Groundwater Sampling Plan 2_28_03.doc 6