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2.04.7 Hydrology Description <br />Total dissolved solids and electro- conductivity diminish as a function of peak <br />flows due to the diluting effect of run -off events. The pH values or acidity of <br />surface waters usually remain stable during peak flows and either increase <br />during low flow due to increased concentrations of caliche derived soluble <br />material, or decrease due to higher concentrations of humic material, <br />depending upon vegetation influences on the drainage basin. <br />(3) Mining in the B -Seam and D -Seam could dewater saturated portions of the <br />seam and may temporarily dry the B -Seam and D -Seam outcrop and the <br />related springs and seeps. After mining, the eastern section of the mine <br />should fill with water to approximate premining levels. The water quality in <br />the mine could be degraded because it will be exposed to collapsed strata. <br />The probable impact would be an increased concentration of TDS, iron and <br />manganese and possibly sulfate. Although no data for permeability or <br />transmissivity of the saturated portions of the coal bearing member of the <br />Mesaverde Formation are available within the permit area, the experience by <br />others (Brooks, 1983) suggests the Mesaverde Formation transmits little <br />water. Therefore, the coal mining operation is not expected to result in the <br />contamination, diminution, or interruption of an underground or surface <br />source of water. The surface drainage system in the surface facilities area <br />will not be interrupted. The mining operation could impact the surface <br />drainage system by increasing the sediment load in the streams. This impact <br />should not occur because run -off from disturbed areas will be passed through <br />sediment ponds or some other form of alternative sediment control. Mine <br />water discharge could impact the surface drainage system by mixing mine <br />water with surface water. Mine water is typically high in total dissolved solids <br />(TDS) relative to surface water so mixing mine water with surface water <br />would be expected to increase the TDS of the resultant mix. <br />B -Seam mining in the western permit area, although unlikely, could impact <br />springs seeps, ponds, Terror Creek and the stream formed by Stevens <br />Gulch. Terror Creek is protected from the affects of subsidence by a limited <br />extraction zone. <br />Hubbard Creek, Terror Creek, West Terror Creek and Stevens Gulch are <br />located in the east, central, north and west portions of the permit area <br />respectively. Hubbard Creek and Terror Creek are protected from <br />subsidence by limited extraction zones. West Terror Creek and Stevens <br />PR -14 2.04-58- 06/14 <br />