2012-07-02_REPORT - C1980007 (3)

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West Elk Mine 2011 Annual Hydrology Report 43 4.2 Water Rights MCC diverts water from the North Fork of the Gunnison River via the Mt. Gunnison Pipeline water right for surface and in -mine processes and potable uses. Approximately 286.97 ac -ft of water was diverted using this water right during WY 2011 (MCC, 2012). Because the Mt. Gunnison Pipeline (Structure ID: 1882) is a relatively junior water right, it may be called out of priority during the late summer and early fall. In WY 2011, two calls were placed on the Mt. Gunnison Pipeline water right in August and September (CDWR, 2012). Out -of- priority diversions are augmented using releases from MCC's water right to Sylvester Gulch and /or leased water released from East Beckwith Reservoir (a.k.a. Lost Lake Slough). 4.3 Sedimentation Ponds The sedimentation and treatment ponds (Figure 9) at the mine site are utilized to manage groundwater collected in the mine, stormwater runoff, and wastewater treatment effluent. All of the ponds except MB -5 and MB -3 are lined with HDPE materials to reduce seepage. Late in WY 2010, pond MB -5 was reconstructed into a large two - celled sediment pond called MB -5E. There are now two "freshwater" ponds (FW -1 and FW -2) that are used to equalize diversions from the North Fork of the Gunnison River and provide water storage. These ponds serve as the raw fresh water supply for the mine's domestic water use and surface and in -mine water needs. 4.3.1 Ponds MB -1 and MB -2R Ponds MB -1 and MB -2R collected mine site stormwater runoff until new sediment pond MB -5E was constructed and made fully - operational in late WY 2010. Stormwater runoff and effluent from the WWTP that had flowed to these ponds is now being diverted to sediment pond MB -5E and until MCC's renewed CDPS permit is approved, any discharges from the new pond will be routed to and through the approved discharge point (004) for pond MB -2R. Water from these ponds can be discharged into either the North Fork of the Gunnison River or transferred to ponds FW -1 and FW -2 per MCC's water storage rights. Pond MB -1 is now freshwater pond FW -2 and pond MB -2R has been filled -in and is the location of the Stacktube 5 coal stockpile. MCC's sediment June 2012 HydroGeo, Inc.