2018-09-04_REVISION - C1980007 (11)

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48 b. Surface Water Effects The West Elk Mine has installed a system of ditches and ponds for controlling sediment eroded from areas disturbed by mining activities. Drainage from undisturbed land is diverted around the site. Almost all drainage from disturbed areas is collected in ponds and treated on-site. There are several small, isolated areas where drainage is not routed to a sediment pond; in these areas, alternative sediment control methods (silt fences, mulch, etc.) are used for controlling sediment. A system of lined and unlined ditches convey water from the disturbed areas to six sedimentation ponds that have been constructed for the surface facilities area. These are: MB-3 Small lower pond MB-4 Train loadout pond MB-5E Bear pond SG-1 Upper Sylvester Gulch pond NSSA North Soil Storage Area pond RPE ponds Refuse pile expansion area With the exception of pond SG-1, all sedimentation ponds discharge directly into the North Fork of the Gunnison River. The mine operation has obtained the appropriate NPDES permits for the discharges. Effluent quality for the sedimentation ponds has been monitored and will continue to be monitored to determine permit compliance. With the exception of occasional WET test failures for microorganisms, and isolated exceedances of suspended solids discharge limitations, the mine has not had recurring problems complying with surface water quality standards. The NPDES permit allows for a discharge of 10,000 gpd, based on a 30-day average, from MCC’s sanitary waste water treatment plant. The potential impact of discharge of waste water effluent would be greatest when the dilution ratio for effluent is smallest. After mining is completed at the West Elk Mine, the underground workings may flood to a point where mine water discharges to the surface either through a perpetual drain that MCC may construct at the down-dip end of the workings next to State Highway 133, or as seepage from the coal outcrop on the hillside south of the highway (if the drain is not constructed). The maximum discharge is predicted to be around 100 gpm. The discharge would likely be relatively high in dissolved solids (on the order of 1,500 to 5,000 mg/l total dissolved solids). The maximum 100 gpm discharge would be diluted to near premining quality by water in the North Fork of the Gunnison River, where flow is always more than 4,500 gpm and total dissolved solids are less than 200 mg/l. MCC predicts the quantity of its water use will not adversely affect the hydrologic balance. Snowmelt provides most surface water flow in the