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

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West Elk Mine The proposed longwall mining operation within the current permit and South of Divide permit revision area could potentially affect water supplies and water rights in the Dry Fork and North Fork drainages. Each drainage and its accompanying water rights that could potentially be affected by subsidence are discussed below. Following this discussion is an evaluation of the water rights aspects of the sealed panels sumps, fault inflows, and MCC's North Fork diversions. In the following analysis, the term "depletion' is calculated as diversions minus return flows. Dry Fork Drainage MCC has a comprehensive decreed water augmentation plan (86CW38) in place to mitigate the possible mining related depletions to Minnesota Creek and its tributaries. Over 80 percent of the South of Divide permit revision area mining is planned in the Dry Fork basin, a tributary to Minnesota Creek which, in turn, is tributary to the North Fork near Paonia. No portion of the Box Canyon permit revision area is within the Dry Fork basin. All of the mining operations in the Dry Fork basin are covered by the augmentation plan. The augmentation plan did not become active until longwall mining first occurred in the 12NW panel (July 1998), the first panel longwall mined, within the Dry Fork drainage. The plan is based on the continuous measurement of several streams (including diversions and reservoir storage volumes) to predict the expected runoff from basins above the mining operations. The expected runoff is compared with actual measured runoff. If actual is less than expected, MCC is required to provide augmentation water as specified in the decree. A copy of the augmentation decree is provided in Exhibit 52. Furthermore, MCC does not anticipate the disruption of flows in Dry Fork due to mining activities in the. SOD permit area. However, under a worst possible scenario, the flows could enter a surface subsidence crack and possibly enter the mine workings. Under such circumstances, MCC would detect the reduction in flow via the water monitoring program and surface observations, as well as the inflow of water into the mine. MCC would then implement the mitigation measures outlined in the permit, which would likely result in identification of the channel section affected and conveyance of flows across the reach. Until long term mitigation measures could be implemented, flows would be conveyed beyond the impacted reach via culverts. The amount of flow lost to the downstream users would be dependent on the time of year and time to implement the nutigation measures. The yield of Dry Fork basin is minimal, but the channel also carries water imported via the Deep Creek Ditch. The Deep Creek Ditch imports about 720 acre-feet (AF) per year and typically runs from May into September. Much of this water is stored in Minnesota Reservoir during the runoff for release later in the irrigation season and diversion by ditches along the mainstem of Minnesota Creek. The 1\4innesota Creek Augmentation Plan is predicated on providing replacement water to irrigation ditches downstream of the confluence of Minnesota Creek with Dry Fork by curtailing diversions controlled by MCC. Depending on the location of the calling water right, the curtailment could result in providing consumptive use credits or full diversion credits. Deep Creek Ditch water that was prevented f'om reaching storage in Minnesota Reser?%orr would Ifkeiy be auginerited by cuitailineiit Qt seiiior irrigation rights.. when in priority. The Auginentation Plan also has over 98 AF of storage water rights within Lone Cabin and Beaver Reservoirs. If the direct flow rights are not in priority when augmentation water is needed, the reservoir 2.05-209 Revised June 2005PRIO; Rez& March.2006; Rev. Apri12006 PR10; May 2006 PRIO;Sep. 2007PR12:Feb 2008 PR12