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West Elk one • Predicted Subsidence Related Phenomena and Material Damage Which Would Occur as a Result of Subsidence - 2.05.6 (6)(b)(i)(B&C) Predicted subsidence impacts for the mining azea have been described in detail in the following section entitled "Subsidence Prediction" 2.05.6 (6)(e)(i). Given the magnitude of the subsidence projected in the above referenced sec$on, the following outlines the material damage which could result as a consequence of the projected subsidence. Structures in the permit azea aze described in Section 2.05.6 (6)(a)(i & ii). The discussions in Section 2.05-6(6)(exii)(A-C) and Section 2.05.6(6)(f)(iv)(A-D) include the "worse possible consequence" to these structures, as well as mitigation commitments. There are 13 stock ponds in or near the Apache Rocks permit revision area and only one stock pond in the Box Canyon permit revision area. There aze 24 stock ponds within the South of Divide permit revision area. The stock pond embankments aze not expected to be impacted, however, the ponds will be monitored and any subsidence impacts mitigated by MCC per the USFS agreement letter in Exhibit 19C. The most significant surface impacts aze expected to occur along the precipitous slopes and cliffs immediately north of the Minnesota Reservoir and in those azeas within the influence of longwall mining where the overburden thickness is less than 400 feet. The azeas with overburden less than 400 feet include approximately 30 acres along the western reaches of Longwall Panels E2-E5. Accounting for this small azea, the minnnum overburden thickness above mining in the South of Divide permit revision azea is 375 feet. In all of these azeas, the most severe hydrologic scenarios • aze as follows: • As discussed in Section 2.05.6, Maximum Depth of Surface Cracks, development of cracks as much as 100 feet deep above the chain and bazrier pillars could divert interrnittent surface and/or spring flow into the more impermeable rocks in the overburden. The probability of such surface cracks occumng is very small. For example, based upon MCC nursing of longwall panels to date, only a few surface cracks have been observed that aze considered to be solely related to B Seam mitring. As discussed later, there aze many "healing" and "sealing" mechanisms that act to close surface cracks. In the event that a surface crack opens and stays open, surface and spring flows that encounter relatively permeable zones in the overburden will move downgradient and likely reemerge as springs with subsequent dischazge into the Dry Fork. W WE and Mr. Dunrud have determined that there is virtually no potential for a surface crack in the permit azea to be deep enough to connect with a mine fracture zone. In the extremely unlikely scenario in which this occurs, however, the implications would be minor. If this scenario were to happen in the Dry Fork basin, surface and/or spring flows could be dischazged into the mine workings. Waters collected within the mine workings would be treated, if necessary, to comply with the National Pollution Dischazge Elimination System (NPDES) permit requirements and pumped through a drill hole back into the Dry Fork basin, as specified in the water augmentation plan (Exhibit 52). bosses within the mine would be minor - ie: less than 5 percent of total inflows. The decreed augmentation plan for the Dry Fork basin conservatively provides replacement water for 100 percent of the yield of the basin. The magnitude of replacement water provided by MCC in the Dry Fork/Nlinnesota Creek basin is • 2.05-103 Revised Jane 2005 PR/0