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West Elk Mine 2014 Annual Hydrology Report 41 <br />4.5.1.2 Outfall 017A Amendments <br />The WQCD deleted effluent limitations and reporting requirements for potentially <br />dissolved iron at Outfall 017A (CDPHE, 2009a and b). <br />4.5.1.3 Bio -Monitoring Testing for Toxicity <br />The acute toxicity limit of LC50 >100% was established in the 2009 amendment. <br />Daphnids (Daphnia magna) and fathead minnows (Pimephales promelas) are used to <br />conduct acute 48-hour whole effluent toxicity (WET) tests (Part I.A.5.a of the permit) on <br />any discharges that include mine water. No WET testing was required in WY 2014 <br />because there was no discharge (MCC, 2015). <br />4.5.2 Sanitary Wastewater <br />MCC maintains an activated sludge wastewater treatment plant to handle sanitary <br />wastewater generated by the West Elk Mine. The WWTP has been in continuous <br />operation since 1982 and was enlarged in WY 1997 to handle up to 20,000 gallons per <br />day. <br />As shown on Figure 10, the WWTP (Outfall 007A) discharges into pond MB -5E where <br />the effluent mixes with stormwater runoff stored in the pond, prior to discharge to the <br />North Fork. Both discharges from the WWTP and pond MB -5E are monitored by MCC, <br />as required by the CDPS permit. In WY 2014, 8.8 ac -ft were discharged from the <br />WWTP to pond MB -5E, but there was no discharge to the North Fork (Figure 10) (MCC, <br />2015). <br />4.5.3 Sedimentation Ponds <br />The sedimentation and treatment ponds (Figure 10) at the mine site are utilized to manage <br />mine water, stormwater runoff, and wastewater treatment effluent. There was no <br />discharge from ponds SG -1, MB -3, MB -4, MB -5E or the RPE and NSSA ponds in WY <br />2014 (Figure 10) (MCC, 2015). Table 11 summarizes the CDPS discharge permit <br />parameters and limits for the sedimentation ponds. <br />June 2015 HydroGeo, Inc. <br />