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The permit review process for the life of mine permit addressed two <br />quantitative impacts to the surface water regime. Mine inflow quantities <br />and the routing of discharges to Foidel and Fish Creeks were re-evaluated <br />twice during the review. Second, the quantity of water which would <br />discharge from the flooded workings into Fish Creek was evaluated in <br />detail. For additional discussion of these topics, see Section IX, <br />Probable Hydrologic Consequences. <br />Mine inflow waters are derived from the dewatering of the Wadge <br />overburden and the interception of vertical faults which are connected to <br />the Trout Creek sandstone aquifer. During the initial submittals of the <br />permit, total mine inflows at any time were projected at 1.66 cfs, and <br />the mine planned to discharge a maximum of 1 cfs through the Foidel Creek <br />portal, and a maximum of 1.36 cfs to Fish Creek through one or more <br />shafts. After re-evaluating existing mine inflow data, it was determined <br />that a maximum inflow to the mine would be 310.2 gpm (0.69 cfs). <br />Maximum discharge to Foidel Creek will be 125 gpm (0.28 cfs) and maximum <br />discharge to Fish Creek will be 185 gpm (0.41 cfs). <br />Discharges from the Wadge overburden to Fish Creek along the northeast <br />side of Twentymile Park can be understood in four phases. Prior to <br />mining, in the first phase, the applicant predicts that the Wadge <br />contributes 9 gpm (0.02 cfs) to lower Fish Creek. During phase two or <br />the active operation, contributions diminish to no discharge. In phase <br />three, as the mine progresses and dewatering activities produce a larger <br />cone of depression in the piezometric surface, there will be no discharge <br />and the applicant predicts that the flooded workings will recharge for <br />three-hundred-and-fifty years. Phase four is the discharge of water from <br />the flooded workings into Fish Creek. There is a dramatic difference <br />between the hydrologic regimes of the Wadge during the discharge from the <br />flooded workings and the discharge prior to mining. The Wadge overburden <br />aquifer is transformed from a 75' thick lithified sedimentary sequence, <br />underlain by an low permeability coal, to a 100' thick rubblized <br />sandstone, siltstone, shale and coal conglomeration. This aquifer will <br />discharge approximately 59 gpm (0.13 cfs) to Fish Creek. Although this <br />is over six times greater than the original discharge from the Wadge <br />overburden, it is insignificant in that it will increase base flows <br />between 6.6% and 15% (TABLE 16). <br />The surface water monitoring plan includes the monitoring of sites <br />upstream and downstream of the Foidel Creek Mine portals and mine water <br />inflow discharge points. Fish Creek will be monitored upstream of all <br />surface mining activity, downstream of the discharge point of the Fish <br />Creek borehole shaft and at the mouth of Fish Creek. In addition, the <br />first irrigation headgate below Fish Creek Borehole Shaft will also be <br />monitored. Field parameters will be monitored monthly and full suite <br />samples will be taken quarterly. Surface water monitoring of Trout Creek <br />will occur monthly during the irrigation season at sites immediately <br />upstream of confluence with Middle Creek and Fish Creek. <br />The permit revision application is in compliance with the hydrologic <br />balance requirements. <br />_17_ <br />