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-30- The long-term effects of mining are effects occurring after disturbed areas have been successfully reclaimed. The surface and ground water systems have had sufficient time to equilibrate, sediment control structures have been removed and the quantity and quality of runoff from the reclaimed areas has returned to pre-mining conditions. Spoils aquifers and underground mine workings have resaturated, and ground water passing through the disturbed area discharges in its pre-mining locations. The quantity of ground water flows would equal pre-mining quantities, but its quality would be degraded. The area modeled (Figures 1 and 2) includes the Foidel Creek, Middle Creek, Fish Creek, Grassy Creek, and Trout Creek drainages, and a reach of the Yampa River from its confluence with Trout Creek to the USGS gaging station at Hayden. Data on the smaller drainage basins are available from U.S. Geological Survey gaging stations and from the mine permit applications on file with the Division. Grassy Creek, Fish Creek, and Trout Creek are smaller perennial streams draining the study area. Foidel Creek and Middle Creek are intermittent streams. Data on the quantity and quality of flows in these streams are available in the Seneca II Mine, Foidel Creek Mine, Edna Mine, Energy Mine No. 3 and Grassy Gap Mine permit applications. Specific data on lower Trout Creek are not available, and had to be estimated from other available data for Fish Creek and upper Trout Creek. The Trout Creek area includes several existing mines. These mines include Apex No. 2, Edna, Energy Mines No. 1, 2, and 3, Eckman Park, Middle Creek, Seneca II, Grassy Gap, and Meadows and Foidel Creek. Except for the Middle Creek Mine it is anticipated that these mines will continue operations according to the life-of-mine areas identified in their permit applications. In running the model, it was assumed that all short-term effects occurred at the same time, that all long-term effects occurred at the same time, and that, except for discharge from the underground mines, no "new" water is added to the surface water system. The U.S. Geological Survey water quality model was used to project the cumulative effect of all anticipated mining in the affected area of the Grassy Gap Mine. The results are examined at four geographic locations; lower Middle Creek, lower Fish Creek, lower Trout Creek, and the Yampa River near Hayden. The effects of mining on Grassy Creek (from Grassy Gap and Seneca II) have been input into the results for the Yampa River near Hayden. The effects of mining upon lower Middle Creek are summarized in Table 2. The modeling indicates that mining will increase discharge, total dissolved solids, and total salt load in the receiving stream. The increase in discharge results from the pumpage of ground water from the underground mine workings. This discharge may be sufficient to sustain perennial flow in Foidel Creek and Middle Creek. The increases in dissolved solids concentrations and total salt load would result from the discharge of water from the underground workings, the discharge of runoff and sediment control systems, and the discharge of affected ground water systems to receiving streams. The projected short-term effects would not be expected to limit the use of this water for flood irrigation.