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• Based on conversations with MCC, the E-Seam is close to the elevation of the <br />highway, with the B-Seam approximately 250-300 feet below this elevation. <br />The lowest borehole (B 1) will reach the E-Seam (Oliver Mine workings) at an <br />estimated depth of 70 feet. Intersection of the Oliver Mine workings will assist <br />geological interpretation and analysis of subsidence associated with historical <br />voids likely to be encountered below the proposed refuse pile. This hole will be <br />abandoned and properly sealed with grout at the Oliver Mine level as needed. <br />• The second and third strings of boreholes will be drilled approximately 10 feet <br />into bedrock below the colluvium, except the location described below. <br />• Extrapolation of the F-Seam puts it in the vicinity of Elevation 6,285, making one <br />of the locations in the third string of boreholes able to intersect it (approx. 95 feet <br />in depth). <br />• The upper two boreholes (fifth string) will be drilled to a depth of approximately <br />10 feet into the bedrock. <br />• Optional boreholes B9 and B10 will be drilled, if needed, to a depth of 10 feet <br />into the bedrock. B9 is intended to define the thickness of the colluvium at a <br />higher elevation of the draw and B 10 is intended to define the lateral extent and <br />thickness of the colluvium at a lower elevation near the highway. <br />• A piezometer will be installed in each of the boreholes to measure groundwater <br />levels and selected locations will be finished with an inclinometer. Figure 2 <br />(attached) provides general installation information for two types of piezometers <br />and the inclinometer. <br />• All boreholes will be sealed according to State of Colorado (CDRMS) <br />requirements when completed. <br />Confirmation from logs and field mapping will assist with proposed depths for drilling, <br />but assuming an average of 30 feet for each of these to reach 10 feet below the base of <br />the colluvium, total drilling footage is estimated to be 330-360 feet for the planned eight <br />boreholes with another 60 feet total for the optional boreholes. <br />Existing roads and trails will be used as much as possible to access the proposed borehole <br />sites. If a tracked rig is available for this project, very little additional access preparation <br />will be required. With a four-wheel drive boring rig, approximately 1,330 feet of new, <br />temporary access will be needed, as shown in Figure 1. This access will be constructed <br />to the minimum width necessary (anticipated to be approximately 12-15 feet wide) by <br />windrowing topsoil and subsoil to the side. Following completion of the boreholes, the <br />soils will be pulled back onto the trail and the area seeded. The borehole sites will be <br />similarly prepared and reclaimed. <br />HAENV PERMITTINGUREVISIONS-MINOR\MR-354\East_RPE_Area_Boring_Memo VI.doc