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West Elk Mine 2013 Annual Hydrology Report 43 4.5 Colorado Department of Public Health and Environment, Colorado Discharge Permit System (CDPS) Summary 4.5.1 CDPS Permit CO- 0038776 MCC's CDPS Permit CO- 0038776 was amended in WY 2009 and changes became effective on May 1, 2009. This permit is currently under administrative extension while the renewed permit is being prepared and is issued. 4.5.1.1 Outfall 007 Amendments In 2009, the Water Quality Control Division (WQCD) adjusted applicable TSS limitations for Outfall 007 to 75 and 110 mg /L (30 -day and 7 -day averages, respectively) (Part I.A.l.e.iv). Additionally, the WQCD established mass based, 30 -day average not- to- exceed limitations for BOD5 and TSS, to replace the percent removal requirements of the permit of 5 lbs. /day for BOD5 and 12 lbs. /day for TSS. These limitations are based on a design flow of 0.02 million gallons per day (mgd) and the concentration based on 30- day average limits of 30 mg /L and 75 mg /L for BOD5 and TSS, respectively. Part I.A.I .e.iii of the permit was amended to reflect these changes." (CDPHE, 2009a and b). Table 10. Summary of CDPS Limits for Outfall 007 n.a. — not applicable 4.5.1.2 Outfall 017 Amendments The WQCD deleted effluent limitations and reporting requirements for potentially dissolved iron at Outfall 017 (CDPHE, 2009a and b). 4.5.1.3 Bio- Monitoring Testing for Toxicity The acute toxicity limit of LC50 >100% was established in the 2009 amendment. Daphnids (Daphnia magna) and fathead minnows (Pimephales promelas) are used to conduct acute 48 -hour whole effluent toxicity (WET) tests (Part I.A.5.a of the permit) on any discharges that include mine water. June 2014 HydroGeo, Inc. Discharge Limitations Discharge Limitations Parameter Maximum Concentrations Maximum Concentrations through April 30, 2009 Effective ay 1, 2009 30 -Day Avg. 7 -Day Avg. or 30 -Day Avg. 7 -Day Avg. or Daily Max Daily Max Total Suspended Solids, mg/L 35 70 75 110 Total Suspended Solids, Percent Removal n.a. >85% - Total Suspended Solids, lbs. /day (mass loading) -- - 12 n.a. BOD5 mg /L, Percent Removal n.a. >85% -- - BOD5 lbs. /day (mass loading) -- 5 n.a. n.a. — not applicable 4.5.1.2 Outfall 017 Amendments The WQCD deleted effluent limitations and reporting requirements for potentially dissolved iron at Outfall 017 (CDPHE, 2009a and b). 4.5.1.3 Bio- Monitoring Testing for Toxicity The acute toxicity limit of LC50 >100% was established in the 2009 amendment. Daphnids (Daphnia magna) and fathead minnows (Pimephales promelas) are used to conduct acute 48 -hour whole effluent toxicity (WET) tests (Part I.A.5.a of the permit) on any discharges that include mine water. June 2014 HydroGeo, Inc.