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• 2.04.7 <br />(b)(i) Minimum, maximum, and average flow data identifying seasonal variations <br />of low flow and peak discharge rates are presented in this section and in <br />Volume III, Exhibit 3. <br />Generally, seasonal variations in stream discharge shows peak rates in late <br />spring and early summer (April-July). Low flows begin in October and end <br />in March. Daily peak flows are typically around 12 midnight and low flows <br />are around 12 noon, due to snowmelt. <br />(b) (ii) (A through G) <br />Water quality data identifying seasonal variations are presented in this <br />section and Volume III, Exhibit 3. <br />Generally, seasonal variations in water quality are functions of flow rates. <br />Total suspended solids and flow peaks coincide due to the erosional nature <br />of run-off due to snow melt events. <br />Total dissolved solids and electro-conductivity diminish as functions 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 D-Seam could dewater saturated portions of the seam and may <br />temporarily dry the D-Seam outcrop and the related springs and seeps. After <br />mining, the eastern section of the mine should fill with water to approximate <br />premining levels. The water quality in the mine could be degraded because <br />it will be exposed to collapsed strata. The probable impact would be an <br />increased concentration of TDS, iron and manganese and possibly sulfate. <br />Although no data for permeability or transmissivity of the saturated portions <br />of the coal bearing member of the Mesaverde Formation are available within <br />the permit area, the experience by others (Brooks, 1983) suggests the <br />Mesaverde Formation transmits little water. Therefore, the coal mining <br />operation is not expected to result in the contamination, diminution, or <br />interruption of an underground or surface source of water. <br />The surface drainage system in the surface facilities area will not be <br />interrupted. The mining operation could impact the surface drainage system <br />by increasing the sediment load in the streams. This impact should not <br />occur because run-off from disturbed areas will be passed through sediment <br />ponds or some other form of alternative sediment control. Mine water <br />• discharge could impact the surface drainage system by mixing mine water <br />PR-04 2.04 - 35 - y22/Ot <br />