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West Elk Mine 2014 Annual Hydrology Report 38 4.2 Water Rights MCC diverts water from the North Fork via the Mt. Gunnison Pipeline water right for surface and in -mine processes and potable uses. Approximately 315.8 ac -ft of water was diverted using this water right during WY 2014 (MCC, 2015). 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 2014, a senior water right placed a call on the North Fork from July 18, 2014 to September 30, 2014, causing the Mt. Gunnison Pipeline water right and all other junior rights to augment their uses from the North Fork (MCC, 2015). MCC's out -of -priority diversions from the North Fork are augmented using releases from MCC's mine 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 10) at the mine site are utilized to manage groundwater collected in the mine, stormwater runoff, and wastewater treatment effluent. All of the ponds are lined with high-density polyethylene (HDPE) materials, except ponds MB -5E and MB -3 that are clay -lined and pond MB -4 that is a concrete basin. There are now two "freshwater" ponds (FW -1 and FW -2) that are used to equalize diversions from the North Fork 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 Pond MB -5E Pond MB -5E (that replaced ponds MB -1 and MB -2R) collects stormwater runoff and effluent from the waste water treatment pond (WWTP). Until MCC's renewed CDPS permit is approved, any discharges from pond MB -5E are routed to and through the approved discharge point (004A) for former pond MB -2R. Water may be stored in pond MB -5E 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 ponds are designed to retain water over a period of time so settling of sediment occurs prior to discharge (batch mode). In WY 2014, pond MB -5E did not discharge to the North Fork (Figure 10) (MCC, 2015). 4.3.2 Ponds MB -3 and MB -4 In addition to pond MB -5E, ponds MB -3 and MB -4 also receive stormwater runoff. In WY 2014, no water was discharged from ponds MB -3 or MB -4 (Figure 10) (MCC, 2015). June 2015 HydroGeo, Inc.