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Mountain Coal Compant~ 1999 Annual Hydrology Report West Elk Mine <br />• Mine Water Management Activities <br />North Fork Water Rights <br />MCC diverts water for in-mine processes and potable uses from the North Fork via the Mount <br />Gunnison Pipeline water right. Approximately 434 acre-feet of water were diverted using this <br />water right during WY99. <br />Because the Mount Gunnison Pipeline is a relatively junior water right, it is often called out of <br />priority during the late summer and early fall. However, in WY99, no call was placed on the <br />North Fork. Out-of-priority diversions aze augmented using releases from East Beckwith <br />Reservoir (a.k.a. Lost Lake Slough). Due largely to the fault inflows, MCC was a net contributor <br />of approximately 74 acre-feet of water to the North Fork during WY99. <br />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 operating since 1982 and <br />was enlarged in WY97 to handle up to 20,000 gallons per day. Discharges are made in <br />accordance with CDPS Permit No. CO-0038776. <br />As shown on Figure 6, the WWTP discharges into pond MB-2R, where the effluent mixes with <br />• stormwater runoff and mine water stored in the pond, prior to discharge to the North Fork. Both <br />discharges from the WWTP and pond MB-2R must be monitored by MCC as required by the <br />CDPS permit. The regulated parameters that apply to the WWTP are shown in Table 6. The <br />discharge designation for the WWTP is 007A, and the discharge designation for pond MB-2R is <br />004A. <br />As shown for the WWTP (007A) on Table 8, the maximum concentrations during WY99 for all <br />regulated parameters were less than the corresponding CDPS limitations (Table 7). There were <br />no numeric effluent exceedances in WY99. <br />Table 7 <br />CDPS Effluent Limitations for the WWTP (007A) <br />Parameter 30-Da Avera a 7-Da Avera a Dail Maximum <br />TSS(m /L) 30 45 N/A <br />TDS (m ) N/A N/A Re ort <br />H 6.5-9.0 6.5-9.0 6.5-9.0 <br />Oil and ease No visible sheen No visible sheen No visible sheen <br />BODs (m 2) 30 45 N/A <br />Feca] coliform (colonies er 100 ml) 6.000 12.000 N/A <br />Total residual chlorine (m /L) N/A N/A 0.5 <br /> <br />831-031.510 Page 14 Wright Water Engineers <br />