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_P7_ <br />ground water and quality of surface water. The applicant states that <br />this poor water quality is due to alluvial ground water flow over the <br />Mancos Shale. However, alluvial water quality analyses of the Coal Creek <br />alluvial ground water show water qualities favorably comparing to the <br />surface water qualities. This, in spite of the fact that there are <br />greater exposures of Mancos Shale 1n the Coal Creek Drainage Basin. <br />Continued monitoring of the alluvial ground water at both mine sites and <br />analysis of this data should aid 1n verifying the actual source of the <br />water quality degradation. <br />The water used at the loadout site is pumped from wells completed in the <br />Roaring Fork alluvium. The withdrawal of this ground water is small and <br />covered under a plan of augmentation. Thus, there will be a minimal <br />impact to the quantity of alluvial ground water. <br />Impacts will be minimal to the quality of ground water within the Roaring <br />Fork alluvium at the loadout site. The water exposed to the coal will be <br />either consumed through evaporation and adsorbed on the coal, or be <br />contained in a lined pond. Any minimal infiltration of degraded water <br />will be quickly diluted by the ground water in the highly transmissive <br />Roaring Fork alluvium. <br />One of the potential impacts associated with most mining operations is <br />increased sediment loads to receiving streams. This would be caused 6y <br />surface disturbance which increases soil loss. Unnatural sediment loads <br />to receiving streams could be detrimental in the following ways: <br />1. Fish reproduction, growth rate, and life span could be reduced. <br />2. Stream temperature could be increased. <br />3. Stream channel capacity could 6e reduced. <br />4. Drainage structures and downstream irrigation systems could be <br />clogged. <br />5. Alluvial water tables could be raised. <br />6. Floodplains could be altered. <br />7. Sediment may carry toxic substances that could change water <br />quality. <br />To minimize the potential impacts of sediment loads at this mine, the <br />operator has constructed a sediment control system (see Section XV of <br />this document). This system will treat all mine discharges and surface <br />disturbed runoff such that total suspended solids and/or settleable <br />solids will be reduced to levels of 70 mg/1 and 0.5 mg/1, respectively. <br />The contribution of sediment by this operation, even without treatment, <br />would be small. The surface disturbed area at the mine area is 522 <br />acres, or 0.2% of the North Thompson Creek drainage. The cumulative peak <br />discharge of all ponds at the mine for the 10-year event (assuming <br />coincident hydrograph peaks) is 0.9 cfs, compared with a 409 cfs flow in <br />North Thompson Creek. For the mine to increase the suspended solids <br />Content of North Thompson Creek by 45 mg/1 (the NPDES Standard), it can <br />be Calculated, at the present discharge rates, that the pond discharge <br />~OUit~ hdV@ t0 hdv0 d TSS Concentration of 20,490 mg/l. This level of <br />