2008-03-21_PERMIT FILE - C1980007A (46)

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West Elk Mine Bedrock Springs From the information available, roughly one third of the springs in the permit area can be considered bedrock springs. All of the springs associated with formations are located well above the projected E Seam fractured zone; consequently, these springs will not be measurably affected by fractures extending up from the mine workings. As noted above, if the relevant formations fall within the caved zone or the lower portion of the fractured zone, the springs may be lost and the recharge water may enter the mine workings. Springs associated with the upper portion of the fractured zone may be either lost into the mine workings or they may relocate to a lower elevation. Although highly unlikely, consider an example in which 50 percent of the bedrock springs in the South of Divide permit revision area are in the caved and fractured zone. In this very conservative scenario, the spring recharge water would drain into the mine workings. The implications of this scenario are not significant. 1. The maximum number of springs that would be lost under this scenario within the South of Divide permit revision area is 8. 2. The combined discharge of the relevant springs is, conservatively, 50 gpm. This represents less than 10 percent of the total spring discharges in the permit area. 3. The source water for these springs would be discharged into the mine workings. Losses within the mine workings are estimated to be less than 5 percent. The remaining 95 percent of the inflow water would. therefore be collected, treated and discharged to the Dry Fork or the North Fork. Bedrock springs could potentially be impacted by surface cracks, but the logic presented in the previous section for colluvial/alluvial springs applies to bedrock springs also. Simply stated, there is no significant risk to bedrock springs from surface cracks. In summary, there is a small, if any, potential for springs to be affected by mining-induced subsidence. The majority of springs within the permit area have alluvium or colluvium as their source of water. These springs may be affected by the natural instability characteristics of the steep hillsides within the permit area that may be increased as a result of mining activities. In this situation, the likely response of an alluvial/colluvial spring will be to relocate downgradient. Vegetation supported by the spring would also likely migrate downgradient to the new spring location, i.e. translated effects to habitat and the ecosystem. Bedrock springs are far less prevalent in the permit area and are less likely to be affected by surficial disturbances. In the unlikely event that a spring's bedrock source is intercepted by the fracture zone, the water would enter the mine workings, where it would be collected, treated, and discharged to the Dry Fork or the 'North Fork. iii such an event, vegetation supported by the sprung would lose its water source. However, the probability of this occurrence is remote, in part due to the lenticular nature of the bedrock fonmations, which would tend to limit the recharge area for the spring to an area near the outcrop. 2.05-205 Revised June 2005 PRIO; Rev. March 2006; Rev. Apri12006 PRIO; May 2006 PRIO.Sep. 2007 PR12;Feb 2008 PR12