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MCC has analyzed the use of directional drilling to <br />achieve degasification goals from sites outside the <br />IRA and has noted the following: <br />Based on preliminary plans these types of boreholes <br />alone are inadequate for proper ventilation and <br />efficient mine operations. These methods are <br />already used by MCC where possible. <br />Directionally Drill MDWs from <br />Outside IRAs <br />Directional drilling is limited by the thickness of <br />overburden (or amount of rock) overlying the coal <br />E seam. This limited thickness of overburden <br />precludes the ability to drill exclusively from <br />outside the IRA boundaries and hit the MDW <br />targets needed in the ventilation plan. <br />MCC expended a tremendous effort over athree- <br />year period in an attempt to Snd a means to <br />successfully accomplish degas drainage using the <br />in-mine horizontal drilling system. These holes <br />were drilled in the gateroads of the 14-17 panels <br />and connected to a massive collection system to <br />exhaust the gases from the mine. The conclusion of <br />this effort was that the holes could not be drilled <br />large enough, or stay open long enough, to allow <br />safe mining of the coal (due [o resulting high <br />methane concentrations). They were simply very <br />inefficient collectors of minimal quality gas, due to <br />the limits of the drilling equipment in this <br />application and the location of the gas-producing <br />zones within the overlying strata. In MCC's <br />previous experience in the B Seam approximately <br />13 percent of total mine methane was able to be <br />vented horizontally (extracted from BLM analysis, <br />2007). Any attempt to degas the E seam via the <br />horizontal drilling system would have the same <br />issues and possibly rr~ore due to constraints of the <br />overlying strata. <br />Therefore, use of directional drilling opportunities <br />has been used as much as possible, however <br />because in places the overburden is not thick <br />enough that directional drilling either from outside <br />the IRA is practical oar possible, therefore some of <br />the operations must be, placed in the IRA <br />Helicopter Drilling of IRA Sites <br />For safety reasons, inladdition to, technical reasons <br />regarding weight limits, this altemative was not <br />carried forward for detailed analysis. <br />Comparison ofi Alternatives <br />This section provides a summary of the effects of <br />implementing each al emative considered in detail <br />(Table S-1). Informal+on in the table is focused on <br />activities and cffect~ where different levels of <br />effects or output, can be distinguished <br />quantitatively or qualitatively among alternatives. <br />The analysis assumed that since coal could not be <br />mined economically v~ithout the methane drainage, <br />ventilation shaft and escapeway, the Alternative 1 <br />would result in previously leased coal not being <br />mined from the area affected. As discussed earlier <br />in this chapter, the ono action alternative would <br />likely cause undergror~tnd coal mining operations in <br />the E seam to slow significantly or diminish entirely <br />over time, due to the economic feasibility. <br />Agency Preferried Alternative <br />Alternative 2 - Pro~iosed Action, including the <br />design criteria is the Forest Service's preferred <br />alternative. ~ <br />I <br />5-12 Deer Creek Ventilation Shaft and E Sea i Methane Drainage Wells FEIS ' <br />