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<br />Appendix A-Errata <br />Use Horizontal Boreholes or <br />Longhole Horizontal Boreholes <br />Mine Ventilation Plans including design of <br />ventilation system are approved by MSHA from <br />submittals and measurements made by MCC. <br />MCC expended a tremendous effort over a <br />three-year period in an attempt to fnd a means <br />to successfully accomplish degas drainage using <br />the in-mine horizontal drilling system. These <br />holes were drilled in the gateroads of the 14-17 <br />panels and connected to a massive collection <br />system to exhaust the gases from the mine. The <br />conclusion of this effort was that the holes could <br />not be drilled large enough, or stay open long <br />enough, to allow safe mining of the coal (due to <br />resulting high methane concentrations). They <br />were simply very inefficient collectors of <br />minimal quality gas, due to the limits of the <br />drilling equipment in this application and the <br />location of the gas producing zones within the <br />overlying strata. <br />In MCC's previous experience in the B Seam <br />approximately 13 percent of total mine methane <br />was able to be vented horizontally (extracted <br />from BLM analysis, 2007). Any attempt to <br />degas the E seam via the horizontal drilling <br />system would have the same issues and possibly <br />more due to constraints of the overlying strata. <br />Based on preliminary plans these types of <br />Boreholes alone are inadequate for proper <br />ventilation and efficient mine operations. These <br />methods are already used by MCC where <br />possible. <br />Directionally Drill MDWs from <br />Outside IRAs <br />MCC has analyzed the use of directional drilling <br />to achieve degasification goals from sites <br />outside the IRA and has noted the following: <br />• Directional drilling is limited by the thickness <br />of overburden (or amount of rock) overlying the <br />coal E seam. This limited thickness of <br />overburden precludes the ability to drill <br />exclusively from outside the IRA boundaries <br />and hit the MDW targets needed in the <br />ventilation plan. <br />• It has been MCC's experience drilling <br />directionally in the B seam that directional holes <br />must be drilled such that the producing part of <br />the well above the seam is vertical. This distance <br />was approximately 250 feet in the B seam <br />methane drainage wells and is projected to be <br />150 feet minimum in the E seam methane <br />drainage wells. If such holes fail to achieve <br />vertical in this portion of the well, they are <br />subject to collapse and ineffective as degas <br />holes. <br />• The maximum safe angle of drilling (above <br />this minimum vertical section) that can be <br />achieved by the drilling equipment available is <br />45 degrees. <br />• The drill mast is set at 45 degrees to begin the <br />holes. This angle must be gradually corrected to <br />vertical during the drilling process. <br />• The maximum allowable dog-leg in directional <br />drilling is 4 percent, in order to be able to <br />successfully install casing in the hole. <br />Given the parameters of overburden depth, as <br />it relates to physical constraints of directional <br />drilling, MCC is unable to reach the required <br />methane drainage targets . from outside the <br />roadless boundary. <br />Therefore, use of directional drilling <br />opportunities has been used as much as possible, <br />however because in places the overburden is not <br />thick enough that directional drilling either from <br />outside the IRA is practical or possible, <br />therefore some of the operations must be <br />placed in the IRA <br />17 <br />