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, <br /> <br />• <br />proposed underground mine to the discharge area on lower Fish Creek. The <br />analysis assumed three point sources contributing leachate to the overburden <br />aquifer; the Energy No. 1 Mine, the Eckman Park Mine, and the Foidel Creek <br />Underground Mine. A summation of the analysis, including input and output <br />parameters, is listed below: <br />Input: <br />Longitudinal dispersivity = 1,000 ft. <br />Transverse dispersivity = 250 ft. <br />Aquifer porosity = 0.2 <br />Flow velocity = 0.02 ft./day <br />Aquifer thicJmess = 73 ft. <br />Source concentration = 3,000 mg/1 <br />Retardation factor = 1.0 <br />Decay constant = 0.0 <br />~_ <br />Obs. point x word. = 20,000 ft. <br />Obs. point y word. = 20,000 ft. <br />50-yr. TDS conc. = 0 mg/1 <br />100-yr. TDS conc. = 0 mg/1 <br />500-yr. TDS cow. = 0 mg/1 <br />The analysis shows that in the 500 years following mining, there will be no <br />contribution of TDS from the underground mine through the overburden <br />aquifer to Fish Creek. Therefore, salt loading of groundwater systems will <br />have no measureable effect on stream water quality. <br />Alluvial Water Quantity and Quality <br />The continuous discharge of underground mine water into Foidel Creek will <br />have the effect of maintaining the water table in the alluvium at the level <br />established in the spring during the runoff season. The maximum amount of <br />discharge (650 gpm) is expected to raise alluvial water levels about 5 feet and <br />maintain the water table at the elevation of the streambed throughout the <br />yeaz during mining operations. This effect will probably be felt downstream to <br />the confluence with Middle Creek. The impact of raising the water table in <br />the alluvium will not be adverse; in fact, a higher water table may benefit <br />vegetative production in the floodplain downstream from the mining <br />operations, by supplying continuous moisture to the root zone. <br />The quality of underground mine effluent is expected to be somewhat less than <br />that of baseline surface water quality. Concentrations of dissolved elements <br />such as sodium, sulfate,uon, and total dissolved solids will be increased, and <br />the effluent released to the stream will infiltrate into the alluvial water <br />2.05-53c <br />