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Groundwater <br />Impacts to groundwater in the 5-year permit area consists of dewatering of <br />aquifers, and affects on water quality. Dewatering of the portions of the <br />coal seam containing water and in the lower portions of the Barren member will <br />occur, and will reach a maximum at the furthest extent of mining. Worst case <br />expected mine inflows are 186 gallons per minute,. At present no undermined <br />springs nor monitoring wells have shown any observable impact due to mining. <br />Sylvester Gulch is the only drainage that has been undermined, and inflows in <br />this area averaged 20 gallons per minute for the 1985 water year. State <br />stipulation 2 requires continued annual monitoring of inflows, discharge, and <br />consumption of water within the mine. A spring monitoring plan including <br />monitoring 1 year in advance of retreat mining is also in place. <br />Impacts to water quality could occur from the operations. State stipulation 3 <br />requires water tight seals be placed in the mine to prevent gravity discharge <br />of water from the mine unless the applicant can provide a demonstration that <br />the water passing through rubbleized overburden is of a suitable quality for <br />discharge and a channel capable of handling the discharge will be <br />constructed. No significant impact is expected to groundwater from either of <br />the waste piles to be constructed. Both piles are designed to handle toxic, <br />acidic, alkaline, or combustible waste rock. Monitoring wells have been <br />installed, and drains will help prevent the formation of a large perched <br />aquifer in the piles and infiltration of leachate to groundwater. No <br />significant impacts to groundwater quantity or quality are expected to occur <br />from mining operations in the 5-year permit area. <br />The CHIA analyzed the life-of-mine impacts of the operation as well as the <br />other mines along the North Fork of the Gunnison River. Impacts to <br />groundwater may occur through induced inflows into the mines through faults <br />and fractures, dewatering of the coal, roof, and floor, and subsidence induced <br />inflows. The possible effects to groundwater from waste piles were previously <br />discussed. <br />Dewatering of the coal, roof, and floor are a source of minor inflow to the <br />mine and these seeps normally dry up within 2 weeks after mining an area. <br />These strata store and retain very little water. These slow inflow rates also <br />indicate that water transmitted by these strata should not result in surface <br />water depletion. Therefore, the impacts of this dewatering will not have a <br />significant impact to groundwater resources. <br />Possible subsidence impacts to groundwater include changes in spring <br />discharge, aquifer characteristics, and recharge, and increase in mass <br />movement (landslide) activity. Subsidence control plans have been proposed to <br />control the impacts from subsidence on streams in the area. State stipulation <br />4 requires that when an application is submitted to undermine the Dry Fork of <br />Minnesota Creek that it include a subsidence protection plan based upon <br />monitoring information collected during earlier phases of mining. Landslide <br />activity is not expected to increase significantly due to subsidence effects. <br />Subsidence cracks in soils and unconsolidated materials are expected to fill <br />thus limiting infiltration and the resulting buildup of water in these type of <br />deposits. The impacts to groundwater quality and quantity from the <br />life~f-mine operation are not significant. <br />-8- <br />