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<br />-30- <br />The effect of having two mining operations affecting strata in hydrologic <br />communication with one another would be to decrease dilution within the <br />aquifers and increase the distance a detectable mine water plume would <br />spread. The degradation of water quality in the coal aquifers will not impact <br />ground water use in the general area, since the poor quality and depth limited <br />use originally. <br />The two operations are expected to cumulatively effect the flow in the <br />Purgatoire River stream/alluvial aquifer system. The New Elk Mine is located <br />on the Middle Fork of the Purgatoire River. This fork joins the North Fork of <br />the Purgatoire to form the Purgatoire River. The Golden Eagle Mine is located <br />adjacent to the Purgatoire River downstream from the New Elk Mine. Both <br />operations have undermined and will further undermine the stream/alluvial <br />aquifer systems. The amount of depletion of flow in the Purgatoire River <br />alluvial aquifer has been estimated to be 5 gpm for the New Elk Mine, and 2.3 <br />gpm for the Golden Eagle Mine. The combined predicted depletion of the <br />stream/alluvial system is 7.3 gpm (0.016 cfs) which amounts to approximately <br />0.3Y of the low flow in the Purgatoire River (5 cfs). This minor loss in <br />stream flow would be offset during mining by the discharge of mine waters from <br />the underground workings. The current average discharge is 123 gpm from the <br />New Elk Mine, and 30 gpm from the Golden Eagle Mine. Each mine is predicted <br />to discharge 180 gpm at full development for a total discharge of 360 gpm (.8 <br />cfs). <br />During operations, water quality in the stream/alluvial aquifer system would <br />be affected by the discharge of water from the underground workings and by <br />seepage from existing and proposed coal refuse piles. At the New Elk Mine <br />site, existing and proposed coal refuse piles and mine water discharge add <br />approximately 48 mg/1 to the total dissolved solids concentration during low <br />flow conditions in the Middle Fork of the Purgatoire. This would add <br />approximately 29 mg/1 during the low flow in the vicinity of the Golden Eagle <br />Mine due to dilution by the North Fork. Mine water discharge at the Golden <br />Eagle Mine would add another 41 mg/1 to low flow total dissolved solids <br />concentrations in the Purgatoire. The cumulative effect of the mine <br />discharges and the New Elk refuse pile is to increase the total dissolved <br />solids concentrations by 76 mg/1 in the Purgatoire River at Golden Eagle under <br />low flow conditions. Added to baseline concentrations of 300 mg/1 or less <br />this increase would not limit the use of water for either flood irrigation, <br />livestock watering, domestic or municipal uses downstream. <br />Following mining, mine water would no longer be discharged to the river. Only <br />seepage from the coal refuse piles would continue to effect water quality in <br />the stream-alluvial aquifer system. Continued seepage from the historic New <br />Elk waste piles in the floodplain would add approximately 16 mg/1 to total <br />dissolved solids concentrations in the Purgatoire River under low flow <br />conditions. This increase would not be expected to limit water use. <br />A. Required Findings <br />The Division is able to find, with the acceptance of stipulations in the <br />pertinent sections of this document,that the operations proposed in the permit <br />revision have been designed to prevent material damage to the hydrologic <br />balance outside the permit area. <br />