2020-08-20_REVISION - C1980007 (36)

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build within the pile and cause the water to migrate laterally to a small seepage area at the edge of the site. There have been no visible flows from the pile toe and mid-section underdrain. ii. Mitigation of Groundwater Impacts - The applicant anticipates no degradation of groundwater quality during mining. The applicant will treat any mine water effluent as necessary to meet water quality standards prior to discharge. There will be no uncontrolled mine water discharge after mining is complete that will significantly degrade surface water or groundwater. The operation plan indicates most water used for dust control will be adsorbed on the coal and carried from the mine, thereby minimizing the quantity to be treated. Any discharge will be treated in the sedimentation ponds and discharged as specified in the NPDES permit. The required ground water monitoring plan for the West Elk Mine is described in Exhibit 71 for the South of Divide and Dry Fork lease areas, and in Table 5, Section 2.04 of the permit application for other areas. MCC monitors water quality and water levels in 27 wells in the permit area. Monitoring wells are completed in the following stratigraphic units (in ascending order): the B-seam, the E-seam, a stratigraphic interval between the E and F seams, the F-seam, the Barren Member, and Quaternary alluvium. More than one well is completed in most of the stratigraphic units. Sampling occurs seasonally(three times a year). Parameters monitored include: water level, pH, conductivity, temperature, total dissolved solids, total suspended solids, total iron, and total manganese. Underground or mine water is permitted for discharge at the following locations: Sylvester Gulch fan site, sediment pond MB-1, the Sylvester Gulch mine water treatment facility, Lone Pine Gulch and Minnesota Creek. The Lone Pine discharge has been discontinued, and the portals have been sealed. Mine water is discharged through the main portals to MB-5E and from the mine water treatment facility to Sylvester Gulch. Quality parameters appear to be such that B-seam mine water will be suitable for treatment and discharge under current NPDES/CDPS permit requirements to the North Fork of the Gunnison River. The quality of mine water from the E-seam workings can be expected to be similar to water from the B-seam workings, based on the similar depositional origin of these two seams. 45