2008-02-22_APPLICATION CORRESPONDENCE - C2008086 (43)

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Joint: A fracture surface or parting in rock, usually sub-planar, without displacement and frequently one of closely spaced sub-parallel fractures forming a joint set. Fault: A fracture surface, parting, or series of partings in rock, more extensive than joints, where rock on either side of the surface, or surfaces, is displaced (offset). Percent Swell: The percent increase in volume of intact rock when broken, collapsed or caved into the open space produced by mining. Coal Bump: The sudden release of strain energy that may produce an explosion-like sound and shock waves in locations where stress (pressure) on the coal exceeds its strength. May be accompanied by sudden sloughing from the face of an advancing entry, sudden uplift of floor coal and/or sudden outward movement of coal from a rib. More frequently occurs in room-and-pillar mining during pillar robbing during retreat from a panel, when mining the pillars were stressed by load transfer from the entries and crosscuts driven on the advance into a panel. Rock Burst: The sudden release of strain energy that produces an explosion-like sound, seismic shock waves recorded on seismographs. Rock bursts or coal will generally be violently ejected from ribs, roof and/or floor of mine openings. Generally occurs at depths exceeding 1,500 feet, in stronger rock types and coal seams and in locations where mining has increased pillar and/or rib stress concentrations that exceed the strength of the rock or coal. 3.0 GENERAL MINING INFORMATION Longwall and room-and-pillar mining are planned for the Red Cliff Mine, with longwall mining predominant. The Proposed Coal Lease tract is bounded by the dashed red line on Figure 1. Red Cliff Mine Project and Coal Lease Areas. There has not been any previous mining in the Coal Lease Application area or the Project Area. The following design specifications were developed for the purposes of describing the potential impacts. A final mine plan will be developed and approved by OSM and the Colorado DRMS. Pillar widths and panel design may vary from those described in this section. 3.1 Panel Design Panels in the Red Cliff Coal Lease Application are projected to be arranged in groups of three or four, with the long axis of the panels oriented in a north-south direction, at an angle that will range from roughly 20° to 70° counterclockwise from the Big Salt Wash drainage, the major topographic feature in the Project Area. The projected north-south panel orientation will align the east-west longwall face between 70° and 20° to this major lineament direction. Big Salt Wash and the upper reaches of Buniger Canyon, Hatchet Canyon and Garvey Canyon are between 20° and nearly 90° to the direction of the secondary drainages that feed into Big Salt Wash from both sides (Post Canyon, Lapham Canyon and other unnamed smaller side canyons), and the lower reaches of Buniger Canyon, Hatchet Canyon and Garvey Canyon. This panel orientation should minimize any parallel alignment of both linear drainage features to the direction of the longwall face and, thereby, possible periodic loading of the face supports. A barrier pillar about 200 feet wide is projected to be left between adjacent panel groups. All panels will be oriented in the north-south direction. The longwall panels are projected C-3 DBMS 295