2018-11-05_PERMIT FILE - C1981044 (12)

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COLORADO DEPARTMENT OF HEALTH 40Rationale Quality Control Division Rationale - Page 2 Permit No. CO -0034142 FACILITY DESCRIPTION: This facility utilizes underground and surface mining to produce coal. The surface operation has been completed and is in the post -mining phase. Sources of wastewater from this facility are: 15 surface runoff sedimentation ponds, two continuous discharges of mine drainage, one continuous discharge of groundwater from a spoils area, and one discharge from a domestic wastewater treatment facility (WWTF). Discharges go to the Williams Fork River and the Yampa River. Outfalls 004, 006, 007, 009, 011 - 021 These outfalls are associated with surface runoff sedimentation ponds. The ponds control runoff from reclaimed areas and are designed and constructed to contain flows generated by the 10 -year, 24-hour precipitation event. Outfalls 004, 006, 007, 009, 011, 012, 015 and 017 go to the Williams Fork River. • Outfalls 013, 014, 016 and 018-021 go to the Yampa River. The outfalls are shown in figure 1 in the permit. Outfalls 001 , 005, 008 and 010 previously existed. The ponds and collection ditches have been partially or completely removed. Remaining work will be completed this summer. Enough work has been done already that no discharge can occur. These outfalls have been deleted.. Outfalls 002, 003 and 022 Outfalls O02 and O03 consist of underground mine drainage from mines #9 and #5 respectively, with design flows of 1000 gpm and 2000 gpm respectively (1.44 14GD and 2.88 MGD). Wastewater is treated with a cationic coagulant prior to sedimentation. A11 groundwater from the mines is discharged through outfall 003. Mine U9 has been shut down and will be sealed. As a result, no discharge is eminating from outfall 002. It is not known if discharge will recommence prior to sealing the mine. Outfall 022 consists of groundwater which flows through a spoils area prior to surfacing. Seepage from the mine water dewatering system is also discharged through this outfall. The design flow for this discharge point is 112 gpm (0.161 MGD). No treatment is provided. Discharge is through a cutthroat flume. • All three discharges go to the Williams Fork River as shown in Figure 1 in the permit.