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~- •~ Executive Summary This annual hydrologic report is the eleventh annual report submitted for the West Elk Mine (formerly the Mt. Gunnison No. 1 1sline) and covers the period from 1 October 1991 through 30 September 1992 (water year 1992). The report describes and interprets hydrologic monitoring data collected at the West Elk Mine during water year 1992 and assesses hydrologic impacts. The report is divided into two sections. The first section describes monitoring activities for water year 1992. The second section interprets the hydrologic data collected during the year and relates this information to mining and reclama- tion activities at West Elk to assess the impacts, if any, on the hydrologic balance. This section also addresses hydrologic impacts tha[ might be expected to occur during water near 1993. An extensive baseline monitoring data base has been developed for the West Elk Mine. Opera- tional monitoring started in August 1981 with commencement of construction activities at West Elk. Monitoring data for the period 1 October 1991 through 30 September 1992 show no significant adverse impacts to the hydrologic balance from mining activities a[ the West EIk Mine. ~~.t L Mine inflows during water year 1992 were more\~~~ than during water year 1991. The volume of water discharged from the underground workings in 1992 was about 74 acre feet. Areas being mined during water year 1992 were about as wet as during 1991. n~ St~G3v~rc d 19 ~ 1 '• z 1o a~~~ I%9 0 55 ~c Fk !qu% i3.Z~cFk "~kb'~ Il~,b'r'ck~ Thz quality of mine water sampled in 1992 was good. All discharges were well within NPDES effluent limitations without treatment. There were two isolated incidents o(eflluents exceeding permit limitations on domestic water polishing discharge number 007A. During monitoring period 91/l0/Ol - 91/12/31, actual residual chlo- rine 0.65 vs. permit 0.5; and during monitoring period 92/U7J01 - 92N9/30, actual [oral suspended solids was 76.4 vs. permit 45. Mine water discharge in 1992 was from Portal No. 2 into pond MB-L. 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 Noah Fork of the Gunnison River. Activities at the Lower Refuse Pile also had no measurable effects on surface or groundwater quality during water year i9''2. Underground mining activities did not produce any significant effects on springs, groundwater wells, or surface water monitoring stations during water year 1992. Water year 1993 is expected to be similar to 1992 relative to hydrology at the mine. No significant impacts are expected. 1994 ~ ~,b' L ~c- F~ ~ r9 I ~~ 9ac,-~f 1%90 ; car. S a~-(r ~-~