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West Elk Mine 2008 Annual Hydrology Report 41 <br />The total inflows entering the mine and mine site during WY 2008 were 440.64 ac-ft versus total <br />outflows of 784.55 ac-ft, resulting in a net difference of 343.91 ac-ft (surface discharges). <br />4.2 North Fork Water Rights <br />MCC diverts water for in-mine processes and potable uses from the North Fork of the Gunnison <br />River via the Mt. Gunnison Pipeline water right. Approximately 404.77 ac-ft of water was diverted <br />using this water right during WY 2008 (CDWR, 2009). <br />Because the Mt. Gunnison Pipeline is a relatively junior water right, it may be called out of priority <br />during the late summer and early fall. In WY 2008, two calls were placed on the Mt. Gunnison <br />Pipeline water right in August and September 2008 for 17.95 ac-ft and 26.63 ac-ft, respectively. <br />The Fire Mountain Canal implemented the call (CDWR, 2009). Out-of-priority diversions are <br />augmented using releases from MCC's water right to Sylvester Gulch and/or leased water released <br />from the East Beckwith Reservoir (a.k.a. Lost Lake Slough). <br />4.3 Sanitary Wastewater <br />MCC maintains an activated sludge wastewater treatment plant (WWTP) to handle sanitary <br />• wastewater generated by the West Elk Mine. The WWTP has been in continuous operation since <br />1982 and was enlarged in WY 1997 to handle up to 20,000 gallons per day. Discharges are made <br />in accordance with Colorado Discharge Permit System (CDPS) Permit No. CO-0038776. <br />As shown on Figure 9, the WWTP (007A) discharges into pond MB-2R (004A) where the effluent <br />mixes with storm water runoff and the mine surface operations water stored in the pond, prior to <br />discharge to the North Fork of the Gunnison River. Both discharges from the WWTP and pond <br />MB-2R are monitored by MCC, as required by the CDPS permit. The seven regulated parameters <br />and stipulations that apply to the WWTP for WY 2008 are summarized in Table 10. <br />The maximum effluent CDPS limitations for WY 2008 are summarized in Table 10. The discharge <br />data for the regulated parameters for WY 2008 are summarized in Table 12. As discussed in <br />Section 4.4.1 below, there were four numeric effluent exceedances at Outfall 007A in WY 2008 <br />(MCC 2009). The permit modifications noted in Table 1 l will be effective in WY 2009 (CDPHE, <br />2009b). <br /> <br />June 2009 HydroGeo, Inc.