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-39- reemerge downstream in the same drainage (the Minnesota Creek system) or it could reemerge along the North Fork of the Gunnison. In the latter case,the impact upon water users located along Minnesota Creek is potentially the greatest. In either case, water users located below the confluence of Minnesota Creek and the North Fork of the Gunnison should not be affected. The following stipulation is required by the Division to insure that the applicant analyzes and uses the data gathered under requirements put forth in previous stipulations. Stipulation No. 11: WEST ELK COAL COMPANY OR ANY SUCCEEDING OPERATOR OF THE MT. GUNNISON NUMBER 1 MINE, MUST SUBMIT TO THE DIVISION AN ANNUAL HYDROLOGIC REPORT. THIS REPORT SHALL INCLUDE AN ANALYSIS OF ALL HYDROLOGIC DATA GATHERED DURING THE YEAR, AN ASSESSMENT OF THE IMPACTS OF MINING DURING THE YEAR, AND AN ESTIMATE OF THE PROJECT IMPACTS OF MINING IN THE FOLLOWING YEAR. THIS REPORT SHALL ASSESS THE IMPACTS OF MINING ON THE QUALITY AND QUANTITY OF WATER IN SURFACE STREAMS, SPRINGS, GROUND WATER AQUIFERS, MINE INFLOW AND MINE DISCHARGES. Impacts on Surface Waters The Division, based on review of the permit applications for the mining operations considered in this assessment, has identified several possible effects of mining on surface water quality and quantity . Surface water quality might be affected by the discharge of mine water from underground workings or by seepage from waste rock or coal refuse piles to the stream - alluvial aquifer system. The underground mining operations, by altering ground water flow, reversing hydraulic gradients, and through subsidence effects, may deplete springs and seeps or stream flows. In addition, the withdrawal of surface water for mine usage may deplete surface flows. Two other possible surface water effects increased infiltration in the areas overlying underground workings and increased erosion from disturbed areas, were briefly considered but then deleted from further analysis. Although subsidence might logically increase infiltration rates in an undermined watershed (and therefore decrease runoff), the Division is unaware of any literature documenting that this effect actually occurs. Surface flow from disturbed areas would carry higher sediment concentrations than natural runoff. However, Rule 4.05.2 requires that all disturbed flow pass through a properly designed sediment control pond. Effluent from the pond is required to meet NPDES limitations prior to discharge. During operation, monitoring and inspection by the Division ensures that the sediment control system is maintained to function as designed. At the close of operations, surface disturbances would be reclaimed and the sediment control system would be removed following the ensuing liability period. As a result, the increased sediment load carried by disturbed flows would not be expected to reach receiving streams.