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Colorado Department of Health water quality standards. Discharge Sites 001 and 004 have been <br />inactivated since operations ceased. Outfall 002 has been retained as a back -up system for the <br />South Mine, with new Outfall 016 now operating as the primary mine -water discharge site. <br />Potential impacts on alluvial water quality due to mine water discharges were discussed <br />previously in Section B.H.A. of this document. <br />Strata Overlying the Cameo Coal Seams <br />The unit directly overlying the Cameo coal seams consists of interbedded sandstones and shales <br />of discontinuous lateral extent. Consequently, the stratigraphy indicates that the entire sequence <br />of strata overlying the coal zone in the permit area behaves as a single hydraulic unit which <br />contains only localized perched aquifers in areas where it is recharged by the river. Groundwater <br />moves slowly through and between interconnected sandstone and shale lenses and beds. <br />The Cameo Coal Seam <br />The third water bearing zone is the Cameo coal seam. Water quality is poor and quantity is <br />insufficient for beneficial use. Water discharge occurs primarily as virgin coal seams are mined <br />and drained locally. Discharge rates vary over time, indicating that saturated zones may be <br />discontinuous over the permit area. <br />Rollins Sandstone <br />The fourth water bearing zone is the Rollins sandstone, which is stratigraphically below the coal <br />seam to be mined This unit is comprised of a clean, tan-to -cream sandstone that ranges from 89 <br />to 114 feet thick throughout the permit area. Due to the extreme depth (from 50 to 1900 feet <br />below surface) and location of the mining operation, it is believed that no damaging effect to the <br />hydrologic properties of the Rollins will occur. To date, there has been no significant impact on <br />this unit. <br />Additional issues that affect the hydrology of the site include waste pile impact on groundwater <br />supplies, in particular leachate generation. The effect of leachate from the Roadside coal <br />processing waste pile (RSRDA) on water quality is negligible. Using the worst -case scenario, <br />where all precipitation enters the waste pile, an average of 0.01 cfs would enter the Colorado <br />River via alluvium percolation. This would have the effect of raising the total dissolved solids <br />content of the Colorado River by 0.01 percent. There is no evidence that leachate from the pile <br />has ever reached or affected the Colorado River. <br />The two other refuse piles, CRDA Nos. 1 and 2, located across the Colorado River from the <br />facility area, have more hydrologic control due to geographic and structural features. All <br />leachate, should it occur, is routed to sediment ponds. CRDA No. 1, in addition, has a series of <br />rock underdrains that would channel the leachate to the sediment pond directly. Since neither <br />CRDA -1 nor CRDA -2 are underlain by alluvium, the area provides a more stable environment <br />for leachate detection and minimization. During the period of active use, minor intermittent <br />seepage was observed from the rock underdrains beneath CRDA -1, and from widely scattered <br />seep areas on the CRDA -1 and CRDA -2 bench outslopes. <br />Groundwater Quantity <br />Permit Revision No. 5 32 July 10, 2012 <br />