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<br />• <br />EXECUTIVE SUMMARY <br /> <br />This annual hydrologic report is the seventh <br />annual report submitted for the Mt. Gunnison <br />No. 1 Mine and covers the period from 1 October <br />1987 through 30 September 1988 (water year <br />1988). The report describes and interprets hydro- <br />logic monitoring data collected at the Mt. Gun- <br />nison No. 1 Mine during water year 1988 and <br />assesses hydrologic impacts. <br />discharged from the underground workings in <br />1988 was 16.8 acre feet versus an estimated <br />33.8 acre feet in 1987. Areas being mined during <br />water year 1988 were drier than during 1987. <br />Precipitation was slightly higher in 1988 than <br />in 1987. Spring runoff and stream flow rates <br />reflected this difference. <br />The report is divided into two sections. The <br />first section describes monitoring activities for <br />water year 1988. The second section interprets <br />the hydrologic data collected during the year and <br />relates this information to mining and reclamation <br />activities at Mt. Gunnison to assess the impacts, <br />if any, on the hydrologic balance. This section <br />also addresses hydrologic impacts that might be <br />expected to occur during water year 1989. <br />An extensive baseline monitoring data base <br />has been developed for the Mt. Gunnison No. 1 <br />Mine. Operational monitoring started in August <br />1981 with commencement of construction ac- <br />tivities at Mt. Gunnison. <br />Monitoring data for the period 1 October <br />1987, through 30 September 1988 show no sig- <br />nificant adverse impacts to the hydrologic balance <br />from mining activities at the Mt. Gunnison No. 1 <br />Mine. <br />Mine inflows during water year 1988 were less <br />than during water year 1987. The volume of water <br />The quality of mine water sampled in 1988 <br />was good and all discharges were well within <br />NPDES effluent limitations without treatment. <br />Mine water discharge in 1988 was from Portal <br />No. 2 into pond MB-1. No water was discharged <br />from the Sylvester Gulch underground sump. <br />Discharged water had no measurable effect on the <br />quality of the North Fork of the Gunnison River. <br />Activities at the Lower Refuse Pile also had <br />no measurable effects on surface or groundwater <br />quality during water year 1988. <br />Underground mining activities did no[ pro- <br />duce asignificant eC(ect on any springs, ground- <br />water wells, or surface water monitoring stations <br />during water year 1988. <br />Water year 1989 is expected to be similar to <br />1988 with respect to hydrology at the mine. No <br />significant impacts are expected. <br />C 1 <br />