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r <br />n <br />t, J <br />f~~~ ~ ~~,.L 1?u~~.r~~ <br />Executive Summary ~~~(1;~~ a,;,~~,k~,~ , <br />This annual hydrologic report is the tenth annual <br />report submitted for the West Elk Mine (formerly <br />the Mt. Gunnison No. 1 Mine) aad covers the <br />period from 1 October 1990 through 30 September <br />1991 (water year 1991). The report describes aad <br />interprets hydrologic monitoring data collected at <br />the West Elk Mine during water year 1991 and <br />assesses hydrologic impacts. <br />The report is divided into two sections. The first <br />section describes monitoring activities for water <br />year 1991. The second section interprets the <br />hydrologic data collected during the year and <br />relates this information to mining and reclamation <br />activities at West Elk to assess the impacts, if any, <br />on the hydrologic balance. This section also ad- <br />dresses hydrologic impacts that might be expected <br />to occur during water year 1992 <br />An extensive baseline monitoring data base has <br />been developed for the West Elk Mine. Operation- <br />al monitoring started in August 1981 with com- <br />mencement of construction activities at West Elk. <br />Monitoring data Cor the period 1 October 1990, <br />through 30 September 1991 show no significant <br />adverse impacts to the hydrologic balance from <br />mining activities at the West Elk Mine. <br />~~ ..~ <br />„~:.. Y~~.4! <br />'' ~Svr,3fr ;.e <br />vJ <br />Mine inflows during water year 1991 were more <br />than during water year 1990. The volume of water <br />discharge•A from the underground workings in 1991 <br />was about 76 acre feet. Areas being mined during <br />water year 1991 were about as wet as during 1990. <br />The quality of mine water sampled in 1991 was <br />good. All discharges were well within NPDES <br />effluent limitations without treatment. <br />Mine water discharge in 1991 was from Portal <br />No. 2 into pond M13-1. No water was discharged <br />from the Sylvester Gulch underground sump nor <br />from Portal No. S. Discharged water had no <br />measurable effect on the quality of the North Fork <br />of the Gunnison River. <br />Activities at the Lower Refuse Pile also had no <br />measurable effecu on surface or groundwater <br />quality during water year 1991. <br />Underground mining activities did not produce any <br />significant effects on springs, groundwater wells, or <br />surface water monitoring stations during wafer year <br />1991. <br />Water year 1992 is expected to be similar to 1991 <br />relative to hydrology at the mine. No significant <br />impacts are expected. <br />lJ <br />