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EXECUTIVE SUMMARY xxw~;-;:~:;~z. mww:>s;.:acxxc. a:.scmcx+o~:a~.;~-:»,:xrasa~naexs.~.w •e;.:o;:;^:,-,,:+.;;;;;s:r. »:xae:ae~::x::xr:.x~:;.,--.^yrm~ This Annual Hydrologic Report (AHR) for the West Elk Mine (formerly the Mt. Gunnison No. 1 Mine) covers the period from 1 October 1994 through 30 September 1995 (Water Year 1995). The report is divided into two sections. The fast section describes monitoring activities. The second section interprets the hydrologic data and relates this information to mining and reclamation activities at West Ells to assess the impacts, if any, on the hydrologic balance. This section also addresses hydrologic impacts that might be expected to occur during Water Year 1996. Monitoring in the 1995 Water Year reflects the revised hydrologic monitoring plan approved with TR-71. This differed from previous monitoring in that a full suite analysis is performed annually on all sites. Two wells were installed during the water year: GB-1 and LP-1. GB-1 replaced SG-1 in the Sylvester Gulch alluvium east of the refuse pile. LP-1 was completed in the Rollins sandstone east of the Lone Pine Portal. By nearly al] accounts, the climate during WY 1995 in Colorado was abnormal. Precipitation within the Gunnison River Valley for Water Year (WY) 1995 was 150% of the 1961-1990 average (Johnson, D.L., Natural Resources Conservation Service, Basin Outlook Report for Colorado, October 1, 1995, Lakewood, Colorado). No water was dischazged from the Sylvester Gulch underground sump nor from Portal No. 5. Discharged water had no measurable effect on the quality of the North Fork of the Gunnison River. • Imponed water during Water Year 1995 was 202.3 acre feet. The volume of water dischazged from the underground workings in 1995 was approximately 57 acre feet. With the development mining under Lone Pine and Gribble Gulch(es), azeas being mined during Water Year 1995 were somewhat wetter than during 1994. The sediment control impoundments effectively treated storm runoff water to meet effluent limitations in all instances except for an excursion from MB-2R during the fourth quarter of 1994. Mine water discharge coupled with storm water runoff yielded waters with nominally elevated total suspended solids concentrations. Modifications of the flocculation and sampling protocol have yielded waters which were in compliance for the remainder of the water year. There was an anomalous failure in the acute testing for Ceriodaphnia during the third quarter of 1995 from effluent from MB-2R. Accelerated testing over the subsequent three weeks resulted in "passing" elevations and did not affum a problem. Several deep bedrock wells exhibited changes during the 1995 Water Yeaz. SOM-2H, completed in the F seam, dropped 35' during the water year for a total drop of 65' from baseline water levels. This site is approximately 0.25 miles south of F-Seam activity, but 700 feet south of B-Seam mains. B-Seam activity may be dewatering the F-Seam. Slope failures in the vicinity may be responsible for lowering the water table. E-seam well, SOM 23-H-2, exhibited a 150' increase in depth to water this year, however high humidity levels within the well have historically precluded accurate measurements. This well is located approximately 1.25 miles south of mining activity. A B-seam well, SOM-129-H, AFQt•93.'-10/OS/I3~96(I.38pm1 1 RE~lSED IOr08i96