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IX. Assessment of Probable Hydrological Consequences of Mining and Cumulative <br />y ro ogic mpacts - Ru es an c . <br />A. Probable Hydrologic Consequences <br />The probable hydrologic consequences section of this findings document <br />addresses the effects that the King Coal tline will have on the ground and <br />surface water systems within and adjacent to the mine area. The information <br />used in this assessment is found in Sections 2.04 and 2.05 of the permit <br />application. <br />1. 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 <br />the 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 of 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 <br />channels. However, these effects are moderated by the detention of runoff in <br />the pond and subsequent evaporation of pond water. In general, only slight <br />changes in the hydrologic balance of surface water are expected due to the <br />underground mining 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 />Evaporation of water standing in the pond may also cause an increase in TDS, <br />although the increase above background concentrations (1500-2000 mg/1) is not <br />expected to be large. <br />The Division has determined that probable hydrologic effects on surface water <br />identified above will not preclude use of the water below the point of <br />discharge from the mine. This conclusion is based on the small and infrequent <br />flows relative to the large amount of dilution available in receiving waters. <br />The quantity of surface water is limited on site and the treatment systems <br />should act to mitigate any adverse effects on surface water. <br />2. Ground Water Effects <br />There are two potentially impacted ground water systems within and adjacent to <br />the King Coal operation: the Menefee Formation and the Hay Gulch alluvial <br />system. <br />The probable hydrologic consequences of mining to the Menefee Formation are <br />negligible. The Menefee is essentially dry at the King Coal Mine. This has <br />been historically documented during past operations. Additionally, a drilling <br />program initiated in 1980 for the proposed Shalako Mine (about 1 mile <br />northeast of the King Coal Mine in Hay Gulch) confirmed that the coal and <br />overburden are essentially free of water. Perched aquifers, which may be <br />-13- <br />