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• • Hydrologic Monitoring Activities The hydrologic monitoring program for the Mt. Gunnison No. 1 Mine began in 1974 with the completion of several groundwater observation wells. This preliminary monitoring network was expanded considerably and in 1981, with the approval of the Mt. Gunnison No. 1 Mine Mining and Reclamation plan (M and R Plan), became the "approved" hydrology monitoring program. In 1984, 1987, and 1989 the program was revised. The ]984 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 of the 1990 opening of the "B" Seam. All revisions were approved by the Colorado Mined Land Reclamation Division (CMLRD). The 1990 Annual Hydrology Report contains the following: • Data from Dve continuous Dow monitoring stations; • Data from two U. S. Geological Survey (USGS) continuous Dow monitoring stations; • Data from seasonal water quality sampling at two surface water quality monitoring stations; Surface Water Monitoring West Elk Coal Company's (WECC) surface water monitoring program includes nine monitoring locations (Table 1). The locations of these moni- toring stations arc shown on Exhibit I- Daily Dow estimates (including mean, maximum, and mini- mum Dows) for the five WECC gauges are summa- rized in Appendix A. Except for two stations with a few mechanical problems, the rewrds are complete. 'fable l Summary of Surface Water Moni- [nring Program at the Mt. Gun- nison No. l Aline Slalion hlow~s~ Water Quality wt « Sylvester Gulch Cominuous A 3 limes per year D USGS/WECC Gaging Slalion Cominuous Q 3 limes per yrar D Fall Fork Minnesota we rr Creek Flume Continuous R 3 times per year ~ !~~ • • • I-ower Dry Fork Flume Continuous A 3 limes per year D ~, r . r Upper Dry Fork Flume Continuous A 3 times per year A v ' •r Lick Creek Flume Continuous A 31ima per year A North Fork Upper -- 3 times per year ? North Fork Lower -- 3 limes per year J USGS North Fork gaging Slalion near Somerset Continuous ~ -- • Data from seasonal measurements oC pH, temperature, dissolved oxygen, turbidity, and conductivity at the six stream gauging stations in the Minnesota Creek Basin and Sylvester G u Ich; • Data from seasonal measurements of dis- charge and water quality sampling at seven springs issuing from or below the "F" scam coal; • Data from seasonal water level and water quality measurements at 23 wells; and • Data from measurements of mine water discharges and mapping of inflow locations. Stilling wells at the five WECC gauges began freezing in October. By the middle of the Decem- ber, all were frozen. Thawing began in February, but it was early April bc(ore all stilling wells had thawed. Debris buildup in the Dumes was minimal during 1990 and no data were lost due to debris. In addition to the five WECC monitoring loca- tions, Dow data are available from two USGS monitoring stations. These stations are Minnesota Creek downstream of Dry Creek and the North Fork of the Gunnison River near Somerset, Colo- rado. The North Fork station is located approxi- mately t/a-mile upstream of the mine site. Because the USGS gauging stations arc heated, they were unaffected by freezing temperatures. Data for the ]m