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<br />-25- <br />Recharge to aquifers occurs primarily in the spring and early swnmer when <br />snowmelt and surface water runoff is abundant, and when transpiration by <br />vegetation and evaporation is at a minimum. Recharge to rock aquifers is <br />limited by the permeability of rock strata and the limited recharge area <br />exposed to surface water (e.g. most sandstones are cliff formers). <br />Overlying clayey and silty soils, and shale and siltstone rock strata <br />also limit vertical recharge of underlying sandstone and coal aquifers. <br />Discharges from bedrrock strata are primarily through springs to the <br />surface system. The flow characteristics of the springs are related to <br />1) the lateral extents and thicknesses of the associated aquifers, 2) the <br />distance between the springs and the aquifer recharge areas, and 3) the <br />permeabilities and ground water storage characteristics of the associated <br />aquifers. Springs issuing from laterally discontinuous, thin sandstones <br />(lenticular and interbedded sandstones) which occur close to the aquifer <br />outcrops will flow intermittantly and their flows will fluctuate <br />seasonally; while springs issuing from regionally extensive, thick <br />sandstones or coals which occur at a great distance, from recharge areas <br />will flow perennially and their flows will not signficantly fluctuate <br />with time. <br />C. Surface Water <br />The area of the proposed Foidel Creek Mine is drained by Fish Creek, a <br />perennial stream, and Foidel Creek, an intermittent stream. Both streams <br />flow northeast to Trout Creek and ultimately into the Yampa River (Figure <br />2). <br />Fish Creek has an average base flow of approximately 3 cfs, which is <br />derived from ground water contribution. Boettcher (1972) estimated that <br />roughly 25 percent of the total streamflow in Fish Creek comes from <br />ground water discharge. Peak discharge in Fish Creek near the proposed <br />permit area occurs during the period from March through June, when the <br />combination of snowmelt, incident precipitation and ground water <br />contribution result in discharge rates in excess of 25 cfs (CYCC, 1982). <br />No ground water discharges into Foidel Creek, as is evidenced by the lack <br />of base flow in the stream during the summer and fall. Foidel Creek <br />flows in response to snowmelt in March through June, at a rate as high as <br />6 cfs (CYCC, 1982) and flows during high intensity rainfall events at <br />other times. <br />Surface water quality in the area is affected at the baseline level by <br />farming, road drainage, and previous mining. Concentrations of major and <br />trace constituents vary greatly with the rates of flow and evaporation, <br />and the locality of sampling. Common elements are: calcium, <br />bicarbonate, sulfate, nitrate-nitrogen, total iron, and total manganese. <br />In general, surface water upstream from current mining activities is <br />calcium bicarbonate type, alkaline, moderately saline and high in calcium <br />carbonate hardness (CYCC, 1982). During the two and one-half years of <br />surface water monitoring conducted by Colorado Yampa Coal Company, total <br />