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• <br />-24- <br />Table 2 displays the flow characteristics of the streams affected by coal <br />mining operations which are considered in the general area. <br />The Crystal and Roaring Fork Rivers are similar in quality. Total <br />suspended solids are less than 50 milligrams per liter for much of the <br />year. Total dissolved solids are 200-500 milligrams per liter. (mg/1). <br />With a pH slightly above neutral, heavy metals and trace elements 1n <br />solution are low. All of these are indicators of good water quality. <br />The Coal Creek Basin includes a 26.6 square mile watershed and consists <br />of eight tributary streams. The Coal Basin Mines affect six of these <br />tributaries and a 10 square mile watershed area. Sediment loads within <br />this basin are naturally high. This is due to the steep terrain and <br />large volumes of runoff generated primarily by snowmelt. Water quality <br />is good with total dissolved solids concentration less than 500 mg/1. <br />Both North Thompson Creek and Middle Thompson Creek exhibit similar <br />baseline characteristics. Total dissolved solids content is low, <br />generally between 100 and 300 mg/1. Suspended solids content is also <br />low, except during snowmelt situations or thunderstorm events. <br />The Fourmlle Creek drainage alsa exhibits good water quality. Total <br />dissolved solids concentrations average 150 mg/1, while total suspended <br />,solids concentrations normally fall below 100 mg/1. For comparisons of <br />selected water quality characteristics, please refer to Table 3. <br />Probable Hydrologic Consequences of North Thompson Creek Mine = Ground <br />Water <br />The North Thompson Creek Mines are impacting the quantity and quality of <br />ground water in the North and Middle Thompson Creek drainage basins. <br />These impacts are mintmal, at present. <br />Both the North Thompson Creek No. 1 and No. 3 mines are experiencing mine <br />inflows. The inflow maps, descriptions of inflows and water quality <br />analyses of inflows are within the permit document. The inflow water <br />quality analyses Indicate at least two sources of water. The inflows <br />with low total dissolved solids (TDS) concentrations have water qualities <br />similar to surface waters. This suggests that these inflows may be <br />transmitted directly to the mine workings from the surface water system <br />with very little residence time in the transmltting aquifer. These low <br />TDS inflows are also generally found emanating from fractures beneath or <br />directly ad,)acent to the stream valleys of North and Middle Thompson <br />Creeks. High TDS inflows indicate longer residence time and reactive <br />time with soluble minerals in ttre transmltting aquifer. These inflows <br />represent the dewatering of overlying and underlying aquifers whose <br />ultimate source of recharge cannot readily be determined. <br />The impacts of depleting ground water in overlying and underlying <br />aquifers will be mintmal as long as these aquifers do not add <br />significantly to the depletion of springs and stream flows. <br />