Laserfiche WebLink
Water monitoring conducted by the operator since 1982 has not identified any unanticipated <br />effects on river water quality. Mine water discharges from approved CDPS points will <br />continue to be analyzed annually for the list of parameters in Table 18 -2 of the permit. <br />2. Surface water runoff from disturbed areas on the mine site passes through sediment ponds, <br />with the exception of the small areas discussed in Section C.II. A.of this document. <br />Discharges from these ponds have historically met effluent limits in the mines' CDPS permit <br />except for discharges related to severe storm events. Effects on water quality due to <br />disturbed -area runoff have been and should continue to be insignificant. <br />Gmnndwater <br />Groundwater Quali ty <br />Four hydrologic units have been identified as aquifers that may be effected by the mining <br />operation. These are: Colorado River alluvium, strata overlying the Cameo coal seams, Cameo <br />coal seams, and the Rollins sandstone unit. Each of these will be addressed below as to the mines' <br />probable hydrologic impact. <br />Colorado River Alluvium <br />The Colorado River alluvium consists of silty sand intermixed with gravel along the canyon and <br />mine facility site. The alluvium varies between 0 and 60 feet in thickness and has a hydraulic <br />conductivity of 0.01 cm2. The main concern with the alluvial aquifer is the total dissolved salt <br />(TDS) content that mining contributes to the stream flow. The diminished quality of water <br />discharged from the mine due to salt and sediment loading is improved somewhat by allowing the <br />water to settle out the solids. The discharged mine water is given sufficient time to allow gravity to <br />settle the solids before discharge occurs to the Colorado River. Three NPDES points discharged <br />the mine water during active operations (Nos. 001, 002 and 004) and were subject to Colorado <br />Department of Health water quality standards. Discharge Sites 001 and 004 have been inactivated <br />since operations ceased. Outfall 002 has been retained as a back -up system for the South Mine, <br />with new Outfall 016 now operating as the primary mine -water discharge site. Potential impacts <br />on alluvial water quality due to mine water discharges were discussed previously in Section B.ILA. <br />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 of <br />discontinuous lateral extent. Consequently, the stratigraphy indicates that the entire sequence of <br />strata overlying the coal zone in the permit area behaves as a single hydraulic unit which contains <br />only localized perched aquifers in areas where it is recharged by the river. Groundwater moves <br />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 />31 <br />