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New Horizon Adjacent North Ground Water Monitoring Holes <br />Four boles . are planned to be drilled at each of three sites. Qne of tilese holes at each of <br />the sites Will be drilled as a pilot hole and will he logged with geophysieal toole. The <br />_ _ <br />„ , <br />other three holes will be constructed as groundwater Monitoring holes. After reviewing <br />: the logS from the pilot holes, the depths for the Monitoring holes Will be deterrnined. At <br />each site one monitoring hole will be constructed in the overburden above the coal zone, <br />another within the Coal ZOne,: and third beloW the Ocial <br />All holes will be drilled using a truck-mounted rotary drill rig. The pilot holes will be <br />drilled to a diameter of 5.418" or 5-518" and will be drilled through the lquela Seam, a <br />thin cpaly shale seam usually found between 15 and. 30 feet below the Upper and Lower <br />Dakota Scants which are the seams targeted for mining Each Of the three pilot holes is to <br />be logged immediately after the hole is drilled. Upon review of these logs, the depths and <br />pecifo construction: details for each of the monitoring holes will be decided. <br />The eOristrtiCtion of the monitoring holes is subject to the findings of the geophysical logs <br />from the pilot holes but will follow the following general guidelines (See Figure 1).: Each <br />hole will be drilled to a diameter of approximately Once drilled the hole will be <br />ased with 4" schedule 40 PVC Casing. In the case of the hole that Will monitor Water <br />above the coal zone, the total depth of the hole will be several feet above the Upper <br />Dakota (UD1.) seani, The lower ten feet of casing will be mill-slotted PVC : Above the <br />slotted easing, a soft-formation packer will be placed on the casing and 3/8" bentonite <br />pellets will be poured down the annulus on top of the packer to an elevation of feet <br />above he packer,: Drill cuttings will then be placed on top of the bentonite pellets to <br />depth of five feet from the SurfaCe, Concrete will be used to grant from the surface to the <br />• Op of the drill cuttings. <br />The holes Monitoring groundwater within the coal zone will be drilled tO the bottom of <br />the Lower Dakota (LDx) Semi. Slotted casing will be used from the total depth to the top <br />of the 03 seam, A soft-formation packer Will be installed above the slotted casing and <br />19 feet Of bentonite chips Will fill the annulus above the packer . Drill cuttings Will be <br />placed itt the hole to a depth of Rite feet from the SurfaCe. The final five feet will be <br />grained with Concrete. <br />The holes completed below the coal zone will be drilled to a depth of approximately <br />fifteen to 30 feet below the LDx seam, Slotted easing Will be used from the total depth to <br />just below the bottom of the coal Seam. A soft-formation packer will be placed just <br />below the bottom of the lower seam and 3/8" bentonite pellets will be pouted in to a <br />depth of several feet above the UD1 seam. Drill cuttings will be placed in the hole to a <br />depth Of five feet from the surface. The final five feet Will be grouted With Obnerete, <br />