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Mountain Coa! Company 1998 Annual Hydrology Report West Elk Mine • Introduction Purpose The purpose of this 1998 Annua] Hydrology Report (AHR) is to summarize Mountain Coal Company's (MCC) hydrologic monitoring activities at the West Elk Mine; report the results of these monitoring activities; and describe the significance of the data, pazticulazly with respect to mining activities as they relate to the Probable Hydrologic Consequences predictions. Overview of 1998 Mining Activities Longwall Mining During water yeaz 1998 (WY98), mining was completed in the ]0 and 11 Northeast longwall panels (Map 1). In middle to late July 1998, the longwall was then moved to longwall panel 13. By the end of the water yeaz, the longwall had advanced to 46 cross-cut. Development Mining Development mining during WY98 focused on completion of gate roads and bleeder systems for longwall panels 13 and 13A, the panel to the south of panel 13 (Map 1). Development continued north in the Box Canyon Mains and south in the B South Mains. The azea in the 23 Headgate was developed to establish an operational sump to be utilized during the development of panel • 14. Development in the 14 Tailgate proceeded cautiously as the 14SEHG fault was encountered. Hydrologic Characterization of 1998 Water Year Overall, WY98 was chazacterized by above average snowfail at the higher elevations, which resulted in above average streamflows in the North Fork of the Gunnison River. During WY98, precipitation measured in Paonia was about average until May, which was only 12 percent of average. From May through September, rainfall was approximately 2.8 inches below normal. This dry Spring is reflected in the Minnesota Creek flows in June, which were well below average despite an above average snow pack in April and May. Climatological Data To summarize precipitation information for the West Elk Mine, data were used from the Paonia, McClure Pass, and Overland Reservoir monitoring stations. Snow data, as well as overall precipitation for WY98, were compazed to long-term averages for these stations to categorize the extent to which the weather deviated from normal. For precipitation data, Climatological Data jot Colorado, published by the National Oceanic and Atmospheric Administration were used, and for the snow data, snow station data from the Natural Resources Conservation Service were used. Total precipitation measured at Paonia for WY98 was 79 percent of normal-defined by the 30- • yeaz average (1961-1990). April snowpack was 135 percent of average at McClure Pass and 121 /- 31.5 age 1 Wrig t aver ngineers