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West Elk Mine • Protection of Hydroloeical Balance - 2.05.6 (3)(a-i) The purpose of this section is to assess the probable hydrologic consequences from mining of the E Seam within the South of Divide permit revision area. This includes impacts to the surface water as well as the groundwater systems within the active mining area. The existing surface water and groundwater resources that may be impacted are described in Section 2.04.7. Key findings in Section 2.04.7 include: (1) Many of the streams in the permit area are ephemeral with flows occurring only in response to snowmelt and significant rainfall events. Dry Fork of Minnesota Creek is appazently a perennial stream, flowing only in response to snowmelt runoff and rainfall events. However, because the currently available data does not specifically indicate whether the majority of Dry Fork is ephemeral, intermittent, or perennial, MCC will continue to monitor the flows through the Dry Fork flumes, the interbasin diversion operational data, and visually check the flows in the fall after water is no longer being diverted to Dry Fork to determine if the stream is ephemeral, intermittent, or perennial. Due to the importation of water via the transbasin Deep Creek Ditch, the Dry Fork stream channel carves water later into the summer than would naturally occur. The presence of a couple of springs downstream of Minnesota Reservoir and below the outcrop of the E Seam, may be able to sustain flow in part of the lower Dry Fork reach (the exception is a small portion of the Deep Creek channel in Section 35); (2) The vast majority of springs in the South of Divide permit area aze located at least 400 feet above the E Seam; and (3) With the exception of certain fault systems, groundwater is very limited in the active coal lease area and there aze no groundwater supply wells at the mine or in the immediate vicinity that could be affected by mining. There aze no "aquifers" in the permit area that will be undermined. Hydrologic consequences that are evaluated herein include: • Disruption, loss, or relocation of ephemeral stream or spring flows • Changes in ephemeral stream or spring water quality • Disruption or loss of reservoir or stock pond capacities • Disruption, loss or storage of groundwater in certain formations, which could, in fain, affect the limited water resources in the azea including springs and stock ponds • Changes in groundwater quality as a consequence of groundwater movement from one formation to another or as a result of interception and/or storage of groundwater within the mine • Wetland impacts Information contained in the following sections demonstrates that only in limited circumstances can these probable hydrologic consequences occur within the West Elk Mine pemtit area. A discussion of these circumstances, their consequences, and protection, mitigation, and monitoring measures is ~~ provided. 2.05-174 Revised June 1005 PRIG, January 1006, March 1006; Rev. May 2006 PRIO