2018-09-04_REVISION - C1980007 (11)

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46 colluvial soils and the lack of a groundwater table near the surface in the colluvium, no impacts on groundwater are anticipated. Water monitoring near the site of the soil stockpiles and waste piles, other water quality monitoring stations on Sylvester Gulch, and sites above and below the mine on the North Fork of the Gunnison, provide data on impacts of this refuse stockpile. The wells in the colluvium in the vicinity of the refuse piles have been mostly dry since 2000 or yielded insufficient water to provide an analysis. A leachate study of the F Seam refuse was conducted and included in the application for the permanent refuse disposal site in Exhibit 51 of the permit application. In addition, the effects of B Seam refuse on leachate were also evaluated and can be found in Exhibit 56. The permeability contrast found in the pile will cause most of the leachate to perch within the refuse pile and above the native soils. A shallow water mound will probably 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.