2009-11-13_PERMIT FILE - C1982056A (7)

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SOUTHWEST MINING DISTRICT • The impacts associated with mining the coal from this District are the same as predicted above. In addition to the Wadge Overburden and Twentymile Sandstone, the Fish Creek Sandstone exists over portions of the Southwest Mining District. The Fish Creek Sandstone is localized in this immediate azea, and is approximately 950-1,000 feet above the coal seam. TCC is not predicting any major impacts to the Fish Creek Sandstone. There may, however, be short-term transitory impacts due to subsiding the area. This could result in lowering the Fish Creek sandstone so that any associated springs would issue from a new location. This location may be at a lower elevation than the original point or from a fracrured zone, if present, within the area. These impacts should not injure any party, and if injury does occur, TCC does have the ability to augment any water loss from the unit TCC will monitor the Fish Creek Sandstone unit during mining to detect and quantify impacts, if any. The monitoring program is outlined in Exhibit 14. TCC does not anticipate any impacts to the Twentymile Sandstone unit resulting from its mining in the Southwest Mining District. Monitoring to date does not show any negative impacts to this unit. Likewise, there aze no springs on the mine property issuing from the Twentymile Sandstone, which eliminates the potential to modify the flow regime of a spring. Given the distance, and the depth of overburden, relative to both Fish and Foidel Creeks, no impacts aze anticipated to the surface water system. Please refer to the above discussion concerning surface wafer impacts resulting from the Foidel Creek Mine. Historically, TCC utilized a 25 degree draw angle to determine a required buffer distance from panels 1o structures in order to prevent subsidence impacts. TCC, through its extensive subsidence monitoring work, has collected data • which indicates that the draw angle varies from 16 to 26 degrees. Between 16 and 26 degrees, however, subsidence is minimal, and no significant surface impacts can be ascertained. It is TCC's opinion that a 16 degree draw angle is a more useful planning constraint. Therefore, TCC will utilize a 16 degree draw angle to determine distance from pane] rib-line to structure for providing adequate protection. The calculations supporting this angle of draw aze presented in Exhibit 7D, Revised Subsidence Predictions for Permit Revision No. 2. j4) Ponds. Impoundments and Diversions (a) General. A genera] plan and detailed denim plan for each sediment pond. water impoundment and diversion proposed to be constructed within the permit azea. Ii) Each general plan shall: (A) Be nrenazed bv, or under the direction of. and certified by a qualified registered professional eneineer, or by a arofessional ¢eoloeist with assistance from experts in related fields such as surveying and landscape azchitectwe; (Bl Contain a description map. prepared accordine to 2.10. and cross section of the structure and its location• (Cl Contain preliminary hvdrolotnic and geologic information reguired to access the hvdro]oeic impact of the structure; • TR06-52 2.05-75 02/17/06