GENERAL35442 - Laserfiche WebLink

Home Browse Search

As previously discussed, the effects on ground water attributable to the disposal of coal processing waste in abandoned underground workings will be negligible. The water used in the disposal process will be reused and what ground water comes in contact with the waste would not be significantly affected because this ground water would be in contact with the same material under natural conditions. In addition, the workings will be flooded, creating anaerobic conditions, which will slaw the dissolution of exposed minerals. The disposal of coal processing waste in the Cameo and North Declines is not planned to occur until after cessation of mining. This disposal will be accomplished in a manner that mitigates any effects on the surface and ground water systems. (See Section VI of this document). The existing Cameo coal processing waste pile is underlain by a series of rock drains. Any leachate would enter the sediment control pond. However, the Roadside waste pile directly overlies Colorado River alluvium, therefore, leachate will have an effect on the Colorado River. The effects of leachate from the Roadside coal processing waste pile on water quantity and quality will be negligible. Using worst case conditions, where all precipitation enters the waste pile, an average of 0.01 cfs would enter the Colorado River. Based on chemical analysis of the coal processing waste, this leachate would have a total dissolved solids (TDS) level of 875 mg/1. Even at the lowest recorded flow with the lowest recorded TDS level, the leaching effect would raise the TDS level in the Colorado River by less than 0.01%. The proposed Cameo Refuse Disposal Areas Nos. 2 and 3 will be constructed without rock underdrains. This is based on the results of piezometer monitoring installations at both disposal sites which indicate dry conditions within the surficial material. As such, it is anticipated that foundational areas will not contribute moisture to the piles and that the proposed drainage control systems around the piles will prevent the development of significant phreatic surfaces within the piles. Any leachate from the piles will come from precipitation falling directly onto the piles during construction and percolating through the material to the finer textured alluvial material beneath the piles. The amount of leachate passing into the alluvial material is considered negligible given the low annual precipitation and relatively high precipitation/evapotranspiration ratio of the region. All surface runoff from disturbed areas and refuse piles will be contained by sediment ponds. This water will be released following a 24-hour settling time and any discharge will meet effluent standards. It is difficult to quantify the effects on water quality, since there has been no sediment pond discharge to date. However, the effect on water quality should be minimal following dilution in the Colorado River. Surface water monitoring will determine if the effects are minimal, as expected. The amount of surface runoff water reaching the Colorado River will be slightly lower than pre-mining conditions because of dead storage below the maximum sediment storage level in the sediment ponds. This effect should be negligible, since the amount lost would be, at worst case, 0.07% of the daily average flow of the Colorado River. With removal and reclamation of the sediment control system, runoff should return to normal conditions. -lg_