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areas of the New Elk mine workings as the mains fill. The slurry will be comprised of 34 <br /> percent solids and pumped at a maximum rate of 700 gpm. The slurry will flow down dip <br /> and the coal fines will gradually settle out. Transport water will be pumped out of an <br /> existing borehole at a rate of 462 gallons per minute and recycled to the preparation <br /> plant. The coal fines are expected to fill 70 percent of the mains upon the completion of <br /> the operation. <br /> The applicant estimated that the life of the slurry operation will be 5 years at the <br /> proposed deposition rate. After the operation is completed, the mine will eventually flood <br /> with mine inflows. The borehole that was used to draw off the decant slurry water will be <br /> monitored and will later be sealed. The borehole is located north of, and adjacent to, the <br /> alluvium of the Purgatoire River. Samples of preparation plant water, which are <br /> representative of the expected quality of slurry decant water, exceed receiving stream <br /> standards for nitrate, ammonia, and cadmium. Slurry water will be diluted with inflow <br /> water flowing from up-dip locations. Mine inflows from down-dip locations and under the <br /> Purgatoire River will pass through the settled fines and are expected to be similar in <br /> quality of the slurry decant water. This water is not planned to be discharged to the <br /> Purgatoire River. The statement of probable hydrologic consequences for the mine <br /> begins on page 2.05-58 of the permit application. <br /> In the unlikely event that discharge from flooding does occur, it will be from the East <br /> Portal, located 42 feet in elevation above the river. Other drillholes and mine openings <br /> lower in elevation than the East Portal will be sealed. In the past, mine inflows have <br /> been measured underground at a rate of 120 gpm. Mine inflows are expected to <br /> decrease as the workings flood and the cone of depression flattens out. From <br /> monitoring of the coal seam water level at other locations, the applicant estimated that <br /> water levels in the mine will recover to an elevation approximately 10 feet below the East <br /> Portal. <br /> If the mine were to discharge from the East Portal at the current rate of mine inflow, the <br /> discharge would subsequently be diluted by the relatively large flow of the Purgatoire <br /> River to levels below receiving stream standards for all constituents. To further improve <br /> the water quality of the slurry water, the applicant will convert from sulfuric acid to <br /> hydrochloric acid in the thickener process to reduce the dissolved metals in the slurry <br /> water. <br /> Once the mine workings are flooded, the water quality of the mixed mine water is <br /> expected to meet the Colorado Water Quality Control Commissioner's Ground Water <br /> Standards. The current water quality of the underground mine is used as the baseline <br /> water quality, as pre-mining baseline water quality is not available from this 43-year-old <br /> mine. <br /> -7- <br />