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Mountain Coa! Compani~ 1999 Mnual Hydrology Repot[ West Elk Mine <br />. Introduction <br />Purpose <br />The purpose of this 1999 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 1999 Mining Activities <br />Longwall Mining <br />During water year 1999 (WY99), mining was completed in the western halves of longwall panels <br />] 2 and 13 (Map 1). By the end of the water year, the longwall had advanced to 27 cross-cut in <br />longwall panel 13. <br />Development Mining <br />Development continued north in the Box Canyon Mains and development of longwall panel 13A <br />during WY99 (Map 1). Development in the 14 Tailgate and Headgate proceeded cautiously after <br />the 14SEHG fault was encountered. <br />• Hydrologic Characterization of 1999 Water Year <br />Water Year 1999 (WY99) was characterized by below average snowfall at the higher elevations, <br />which resulted in below average streamflows in the North Fork of the Gunnison River and in <br />Minnesota Creek. WY99 precipitation (measured in Paonia) was slightly above the 30-year <br />average yet varied substantially from month to month in comparison to the historic data. <br />February and March precipitation totals were less than 40% of the long-term monthly averages <br />while April and July were 200% and 240% respectively of the long-term monthly averages. <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 WY99, were compared to long-term averages for these stations to categorize the <br />extent to which the weather deviated from normal. For precipitation data, Climatologica/ Data <br />jar 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 <br />SNOTEL information database were used. <br />Total precipitation measured at the Paonia 1 SW station for WY99 was 108 percent of normal - <br />defined by the 30-year average (1961-1990). Not counting the wet months of April and July, <br />precipitation during the remaining ten months was at 88 percent of the 30-yeaz average. For <br />WY99, snowpack was only 65 percent of the average at the McClure Pass Station, and 75 <br />83/-03?.520 Page 1 If'righr li'arer Engineers <br />