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• Executive Summary This Annual Hydrologic Report (AHR) is the twelfth annual report submitted for the West Ell: Mine (formerly the Mt. Gunnison No. 1 Mine) and covers the period from 1 October 1992 throw h 30 Se tember 1993 water year 1993). The report describes and interprets hydrologic monitoring data collected at the West Elk Mine during water year 1993 and assesses hydrologic impacts. The report is divided into two sections. The first section describes monitoring activities for water year 1993. The second section interprets the hydrologic data collected during the year and relates this information to mining and reclamation activities at West Elk to assess the impacts, if any, on the hydrologic balance. This section also ad- dresses hydrologic impacts that might be expected to occur during water year 1994. An extensive baseline monitoring data base has been developed for the West Elk Mine. Operational monitoring started in August 1981 with commencement of construction activities at West Elk. Monitoring data for the period 1 October 1992 through 30 September 1993 show no significant adverse impacts to the hydrologic balance from mining activities at the West Elk Mine. Mine inflows including imported water during water year 1993 were more than during water year 1992. The volume of water discharged from the underground workings in 1993 was about 40 acre feet. Areas being mined during water year 1993 were about as wet as during 1992. The quality of mine water sampled at 002A during the 1993 water year was good although there was one, unreproducible failure of a ceriodaphnia biomonitoring test in February. Accelerated testing showed insignificant mortality. Discharges from all sediment ponds were well within National Pollution Discharge Elimirtation System (NPDES) effluent limitations without treatment. The sewage treatment pond 007A met all effluent limitations. Mine water discharge in 1993 was from Portal No. 2 into pond MB-1. No water was discharged 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. Activities at the bower Refuse Pile increased iron concentrations in surface water runoff, but had an insignificant effect on surface or groundwater quality outside the permit area. Underground mining activities did not produce any significant effects on springs, groundwater wells, or surface water monitoring stations during water year 1993. Water year 1994 is expected to be similar to 1993 relative to hydrology at the mine. No significant impacts are expected.