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J. Probable Hydrological Consequences <br />The Hay Gulch alluvial valley floor (AVF) has been identified as an aquifer in <br />the study area. The Blue Flame Coal, Ia Plata No. 1 and King Coal Mines <br />Have been designed to minimize, to the extent possible, impacts to the alluvial <br />aquifer. The sediment ponds at the National King Coal operation have never <br />discharged into the AVF. The proposed sediment pond at the Blue Flame site <br />as well as the existing Ia Plata No. 1 sediment pond, have been designated to <br />store the nmoff from a 10-year, 24-hour storm event. No discharge is expected <br />from any of these ponds due to a storm event of lesser ntagninrde, or as a result <br />of snowrnelt. Furthermore, monitoring of the alluvial aquifer down gradient <br />form the National King Coal operation, indicates that the quality of the alluvial <br />aquifer is not being diminished by coal mining operations. Alluvial water <br />quality monitoring programs committed to by National King Coal will help <br />delimit the potential for future impacts to this alluvial system. <br />Due to the hydrologic characteristics of the Hay Gulch alluvial aquifer, and to <br />the manner in which the mining operations are, or proposed to be, conducted, it <br />has been detenttined that no significant cumulative hydrologic impacts to the <br />alluvial aquifer will occur. <br />Pursuant to C.R.S. 34-33-114(2)(C), the Division has assessed the probable <br />cumulative hydrologic impacts to the ground water and surface water basins <br />defined in this document, from permitted and anticipated mining operations. <br />.The Division finds that the King Coal operations had been designed to prevent <br />material damage to the hydrologic balance outside the permit area. <br />Surface Water Effects <br />All runoff from the disturbed area at the mine site will be routed through the <br />two sediment ponds. Effects of mining on this water will involve changes in the <br />magnitude and duration of runoff and changes in water quality. <br />The effects on water quantity are expected to be minimal. An increase in <br />imperviousness due to the construction or roads and buildings can be expected <br />to cause an increase in runoff amounts. The rate of runoff will increase over <br />natural conditions because of the increased efficiency of conveyance channels. <br />However, these effects are moderated by the detention of nmoff in the pond and <br />subsequent evaporation of pond water. In general, only slight changes in the <br />hydrologic balance of surface water are expected due to the underground mining <br />operations proposed at the King Coal Mine. <br />Changes in water quality can be expected to occur as a result of mining. An <br />increase in erosion rates are expected from the disturbance of soils and <br />vegetation, however, these are compensated by deposition of sediment in the <br />sediment pond. An increase in total dissolved solids (TDS) may occur from <br />well water pumped and used for dust suppression and other operational use. <br />15 <br />