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• ~J Hydrologic Monitoring Activities The hydrologic monitoring program for the West Elk Mine began in 1974 with the completion o[ several groundwater observation wells. This prelim- inary monitoring ne[work was expanded consider- ably and in 1981, with the approval of the West Elk Mine Mining and Reclamation plan (M and R Plan), bepme the "approved" hydrology monitor- ing program. In 1984, 1987, and 1989 the program was revised. The 1984 and 1987 revisions were made to more efficiently monitor possible effects from mining and provide data for future permitting. The 1989 revision incorporated provisions for collecting "B" seam baseline data and monitoring for potential mining impacts in anticipation o[the 1990 opening of the "B" Seam. All revisions were approved by the Colorado Mined Land Reclamation Division (CMLRD). Surface Water Monitoring Mountain Coal Company's (MCC) surface water monitoring program includes nine monitoring locations (Table 1). The loptions of these moni- toring stations are shown on Exhibit I. Daily flow estimates (including mean, maximum, and mini- mum flows) for the five MCC gauges are summa- rized in Appendu A Except for two stations with a few mechanical problems, the records are complete. Table 1 Summary of Surface Water Moni- toring Program at the West Elk Mine Slatioo Row Water Quslily The 1991 Annual Hydrology Report contains the following: • Data from five continuous Clow monitoring stations; • Data from two U.S. Geologipl Survey (USGS) continuotu Clow monitoring stations; • Data from seasonal water quality sampling at two surface water quality monitoring stations; • Data from seasonal measurements of pH, temperature, dissolved oxygen, turbidity, and conductivity at the six stream gauging stations in the Minnesota Creek Basin and Sylvester Gulch; • Data from seasonal measurements of dis- charge and water quality sampling at seven springs issuing from or below the "F" seam coal; • Data from seasonal water level and water quality measurements at ?3 wells; and • Data from measurements of mine water discharges and mapping o[ inflow locations. Sylvester Gulch Continuous 3 lima per ywr USGS/MCC Gaging Slatioo Continuous 3 times per ywr £ast Fork Minnewta Crsk Flume Continuous 3 times per ywr Lower Dry Fork Flume Continuous 3 times per ywr Uppv Dry Fork Flume Continuous 3 limes per ywr Lick Creek Rume Continuous 3 limes per ywr Nonh Fork Upper - 3 limes per ywr Nonb Fork Lower - 3 limes per ywr USGS Nonh Fork gaging alatioo near Somerset Cominuous - Stilling wells at the five MCC gauges began freez- ing in November. By the beginning of December, all were frozen. Thawing began in February, but it was mid-April before all stilling wells had thawed. Debris buildup in the flumes was minimal during 1991 and no data were lost due to debris. In addition to the five MCC monitoring locations, flow data are available from two USGS monitoring stations. These stations are Minnesota Creek downstream of Dry Creek and the North Fork oC the Gunnison River near Somerset, Colorado. The Nonh Fork station is located approximately +/a-