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• is, therefore, highly unlikely that mine derived contaminants could discharge into the Yampa River <br />through its alluvial aquifer. <br />(8) With proper disposal practices, solid wastes can be disposed of in all areas of the mine. Disposal of <br />ash or ash -sludge mbdures In Trapper Mine will enhance slope stabilities relative to mine spoil <br />already present. Separate disposal of scrubber sludge can be expected to lead to slope instabilities. <br />(9) Groundwater contamination from disposal of Craig Station fly ash, bottom ash and scrubber sludge in <br />the Trapper Mine is unlikely. Minimal infiltration, the moisture storage capacity of the overburden, <br />significant attenuation capacity of the overburden for contaminants and relative impermeability of the <br />waste to the spoil are the primary reasons for this predicted low probability. <br />4.3.4.1 Description of the Craig Station Generating Plant <br />The Craig Station is a coal-fired electrical generating plant consisting of three steam -turbine generating units <br />with a net capacity of approximately 1,264 megawatts. The coal is crushed and pulverized before burning <br />such that 65 percent of the coal can pass through a 200 mesh sieve. All three boilers were manufactured by <br />Babcock and Wilcox and employ opposed firing. Air is supplied to the boilers by forced -draft fans. <br />• Approximately 17 percent excess air is added at full load to ensure complete combustion. <br />Mechanical -draft closed -cycle cooling towers are used for cooling the condenser water. Drift, evaporation, <br />and blow -down of cooling tower water result in an eight -fold concentration of the raw water make up. The <br />blowdown is used for bottom ash sluicing and as make-up water for the wet SO2 scrubber and dry scrubber. <br />Excess cooling tower blowdown, if any, goes to an evaporation pond and to the mine for road watering. <br />Ash remaining after the firing of the coal is present both as fly ash and as bottom ash. The bottom ash is <br />quenched in the bottom of the boiler and sluiced to <br />