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<br />• <br />EXECUTIVE SUMMARY <br />This annual hydrologic report is the eighth annual <br />report submitted for the Mt. Gunnison No. 1 Mine <br />and covers the period from lOctober 1988 <br />through 30 September 1989 (water year 1989). The <br />report describes and interprets hydrologic monitor- <br />ingdata collected at the Mt. Gunnison No. 1 Mine <br />during water year 1989 and assesses hydrologic <br />impacts. <br />discharged from the underground workings in 1989 <br />was about 13.2 acre feet versus an estimated <br />16.8 acre feet in 1988. Areas being mined during <br />water year 1989 were drier than during 1988. <br />Precipitation was slightly less in 1989 than in 1988. <br />Spring runoff and stream (low rates reflected this <br />difference. <br />The report is divided into two sections. The first <br />section describes monitoring activities for water <br />year 1989. The second section interprets the <br />hydrologic data collected during the year and <br />relates this information to mining and reclamation <br />activities at Mt. Gunnison to assess the impacts, if <br />any, on the hydrologic balance. This section also <br />addresses hydrologic impacts that might be expect- <br />ed to occur during water year 1990. <br />An extensive baseline monitoring data base has <br />been developed for the Mt. Gunnison No. 1 Mine. <br />Operational monitoring started in August 1981 <br />with commencement of construction activities at <br />Mt. Gunnison. <br />Monitoring data for the period 1 October ]988, <br />through 30 September 1989 show no significant <br />adverse impacts to the hydrologic balance Crom <br />mining activities at the Mt. Gunnison No. 1 Mine. <br />Mine inflows during water year 1989 were less than <br />during water year 1988. The volume of water <br />The quality of mine water sampled in 1989 was <br />good and all discharges were well within NPDES <br />effluent limitations without treatment. <br />Mine water discharge in 1989 was from Portals <br />No. 2 and No. 5 into pond MB-1. No water was <br />discharged from the Sylvester Gulch underground <br />sump. Discharged water had no measurable effect <br />on the quality of the North Fork of the Gunnison <br />River. <br />Activities at the Lower Refuse Pile also had no <br />measurable effects on surface or groundwater <br />quality during water year 1989. <br />Underground mining activities did not produce a <br />significant effect on any springs, groundwater wells, <br />or surface water monitoring stations during water <br />year 1989. <br />Water year 1990 is expected to be similar to 1939 <br />relative to hydrology at the mine. No significant <br />impacts are expected. <br /> <br />