Laserfiche WebLink
Colorado Department of Health water quality standards. Discharge Sites 001 and 004 <br /> have been inactivated since operations ceased. Outfall 002 has been retained as a <br /> back-up system for the South Mine, with new Outfall 016 now operating as the <br /> primary mine-water discharge site. Potential impacts on alluvial water quality due to <br /> mine water discharges were discussed 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 <br /> and shales of discontinuous lateral extent. Consequently, the stratigraphy indicates <br /> that the entire sequence of strata overlying the coal zone in the permit area behaves as <br /> a single hydraulic unit which contains only localized perched aquifers in areas where <br /> it is recharged by the river. Groundwater moves slowly through and between <br /> 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 <br /> quantity is insufficient for beneficial use. Water discharge occurs primarily as virgin <br /> coal seams are mined and drained locally. Discharge rates vary over time, indicating <br /> that saturated zones may be discontinuous over the permit area. <br /> Rollins Sandstone <br /> The fourth water bearing zone is the Rollins sandstone, which is stratigraphically <br /> below the coal seam to be mined. This unit is comprised of a clean, tan-to-cream <br /> sandstone that ranges from 89 to 114 feet thick throughout the permit area. Due to <br /> the extreme depth (from 50 to 1900 feet below surface) and location of the mining <br /> operation, it is believed that no damaging effect to the hydrologic properties of the <br /> Rollins will occur. To date, there has been no significant impact on this unit. <br /> Additional issues that affect the hydrology of the site include waste pile impact on <br /> groundwater supplies, in particular leachate generation. The effect of leachate from <br /> the Roadside coal processing waste pile (RSRDA) on water quality is negligible. <br /> Using the worst-case scenario,where all precipitation enters the waste pile,an average <br /> of 0.01 cfs would enter the Colorado River via alluvium percolation. This would have <br /> the effect of raising the total dissolved solids content of the Colorado River by 0.01 <br /> percent. There is no evidence that leachate from the pile has ever reached or affected <br /> the Colorado River. <br /> The two other refuse piles, CRDA Nos. 1 and 2, located across the Colorado River <br /> from the facility area, have more hydrologic control due to geographic and structural <br /> features. All leachate, should it occur, is routed to sediment ponds. CRDA No. 1, in <br /> addition, has a series of rock underdrains that would channel the leachate to the <br /> sediment pond directly. Since neither CRDA-1 nor CRDA-2 are underlain by <br /> alluvium, the area provides a more stable environment for leachate detection and <br /> 35 <br />