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A9oun[ain Coa! Compam~ 1997 Annual Hydrology Report Wes[ Elk A4ine <br />ri Introduction <br />Purpose <br />The purpose of this 1997 Annual Hydrology Report (AHR) is to summarize Mountain Coal <br />Company's (MCC) hydrologic monitoring activities at the West Elk Mine; report the results of <br />these monitoring activities; and describe the significance of the data, particulazly with respect to <br />mining activities as they relate to the Probable Hydrologic Consequences predictions. <br />Overview of 1997 Mining Activities <br />Longwall Mining <br />During water year 1997 (WY97), mining was completed in longwall panels 8NW and 9NW in <br />the Jumbo Mountain permit revision area. The longwall was then moved to longwall panel <br />LONE. As shown on Map ], retreat mining of longwall panel IONE had only just begun in <br />September 1997, the last month of the water year. <br />Development Mining <br />Development mining of the gate road and bleeder entries for IONE and I1NE panels was <br />completed (Map 1). Development of the 12NW longwall panel was also completed. The Box <br />• Canyon Mains had been driven to the north to Cross-cut #13 and the B South Mains were driven <br />to the south to Cross-cut #6. <br />Hydrologic Characterization of 1997 Water Year <br />Climatological Data <br />To summarize precipitation information for the West Elk Mine, data were used from the Paonia, <br />McClure Pass, and Overland Reservoir monitoring stations. Snow data, as well as overall <br />precipitation for WY97, were compared to long-term averages for these stations to categorize the <br />extent to which the weather deviated from normal. For precipitation data, Climatological Data <br />for Colorado, published by the National Oceanic and Atmospheric Administration were used, <br />and for the snow data, snow station data from the Natural Resources Conservation Service were <br />used. <br />Overall, WY97 was wetter than normal for the West Elk Mine vicinity, as well as for the <br />Gunnison River Basin. This coincided with the pattern the state of Colorado was exhibiting. <br />The wet conditions were demonstrated by higher than normal streamflow. Reservoir storage <br />remained at greater than 100 percent of normal for the Gunnison Basin during the water year. <br />Tota] precipitation measured at Paonia for WY97 was 139 percent ofnormal--defined by the 30- <br />year average (1961-1990). Monthly snow depths were well above average for all months except <br />May at McClure Pass and for all months except May and June at Overland Reservoir during <br />• WY97. Overall, measured snow depths at McClure Pass were approximately ]55 percent of <br />31-032.450 image t rig t a[er ngrneers <br />