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YVest Etk Mine <br />Monitorine Freauency - 2.05.6 (6)(b)(I)/D,E & F) <br />Unless as otherwise noted above, the subsidence and seismic monitoring will be performed semi- <br />annually and reported to the CDMG semi-annually, as well. A summary of the visual observations <br />and monitoring of subsidence will be provided in a quarterly letter report to CDMG and to the <br />USFS. <br />Subsidence Control Plan - 2.05.6 (~(b)(iii)(B), (6)(d)(i&ii). (6)(e)(iv) & (6)(n(i-vii) <br />Description of Mining Methods - 2.05.6 (6)(fl(iv)(A& B) <br />As discussed in Section 2.05.6(6)(e)(i)(A), Brief Description of Mining Method, the longwall <br />mining method is planned for Apache Rocks and Box Canyon mining areas. An east-west panel <br />layout, is planned except for the two northeast panels (LONE and 11NE) which aze orientated in a <br />north-south direction. Longwall mining of the E Seam (in Sections 32, 33 and 34 of T13S and in <br />Section 3, 4, 9 and 10 of T14S) is planned in the South of Divide mining azea. Although longwall <br />mining may initially induce more caving and fracturing of the roof rocks as compared to the room- <br />and-pillaz method due to the complete removal of coal in the panel, it offers the advantages of <br />maximizing resource recovery. The longwall method also causes more uniform subsidence (full <br />extraction of panel) and causes equilibrium conditions to be reached in a shorter period of time (i.e., <br />there is no additional, lingering pillaz crushing in panels). <br />Preventive Measures - 2.05.6/6)/n/iii) <br />• State-of--the-art longwall mining technology will continue to be utilized for extraction of the B <br />Seam and for the extraction of the E Seam in the permit area. Although longwall mining may <br />initially induce more caving and fracturing of the roof rocks, as compared to the room-and-pillar <br />method, it offers the advantages of maximizing resource recovery; more complete subsidence; <br />equilibrium conditions occumng in a shorter period of time; more uniform and predictable <br />pazameters necessary for the evaluation of probable hydrologic consequences; and in general, <br />fewer and less significant adverse hydrologic impacts than room-and-pillaz mining. <br />Anticipated Effects - 2.05.6 (6)(fl(iii)(A <br />Long-term impacts on the surface are predicted to be minimal above the longwall panels. The <br />few surface cracks over the mining panels that may occur aze expected to close once the longwall <br />face moves past the surface area of influence. Surface cracks present above the chain or barrier <br />pillazs or mine boundaries may remain open where permanent tensile strains remain after mining <br />is completed. However, at least several hundred feet of unfractured rock will typically exist <br />between any mine-induced surface fractures and the upper part of any mine-induced fractures <br />above the caved zone in the mining panels. Therefore, from a practical standpoint, no <br />interconnection between the surface fractures and the mine workings is anticipated. Again, <br />under a worst case scenario, if a surface fracture were to occur concurrently within an area <br />controlled by faults or bedrock lineaments, there could be interconnection between adjacent <br />sandstones. However, even under these conditions, the fractures would most likely not extend <br />through the claystones and shales present in the overburden. <br />• Monument Dam and Minnesota Reservoir aze located outside of the angle of mining influence of <br />the nine projected panels (panels E1 through E9) for the South of Divide mining azea (see Map <br />1.05-169 Revised June 2005 PRIO, Rev. March 2006; May 1006 PRIO <br />