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of four sediment ponds constructed below the loadout facilities serve to maintain water quality at disturbances in this drainage. Monitoring data collected during the past five years support this conclusion. Water Quantity Effects The quantity of water in the Trout Creek basin will not be increased or decreased as a result of mining. A small change in the partitioning of total runoff into surface and subsurface components is the only anticipated effect of mining on the overall water balance. Prior to mining, the ratio was 7 percent surface runoff to 93 percent subsurface runoff. During mining, the predicted ratio changes to 4 percent surface flow and 96 percent subsurface flow. The post-mining landscape of the Moffat Area will be regraded and topsoiled to the same general topography as currently exists. It is expected that the mean slope and infiltration capacity of the area will eventually be very similar to the pre-mining conditions. An increased potential maximum ground water retention is expected, but not of the magnitude that will significantly affect the surface water balance over time. Therefore, about the same partitioning into overland runoff and infiltration is expected to occur in the post-mining phase as now exists. Between the time that mining occurs and the time that full revegetation has been accomplished, evapotranspiration may be reduced relative to current water consumption by vegetation. A corresponding increase in subsurface runoff will occur. Reclamation activities will eventually establish a plant cover with a water demand very similar to that which now exists. Possibly the most significant factor that could substantially affect the post-mining water balance is a change in the effective rooting depth and the total available water-holding capacity of the root zone. Again, such a change is difficult to accurately predict. The interface between the topsoil and the spoil may serve to reduce downward movement of water and cause the available water-holding capacity to be greater than in the undisturbed state. Changes in evapotranspiration and the partitioning of runoff into surface and subsurface components due to the factors discussed above are expected to be small. Therefore, the post-mining water balance is estimated to be virtually unchanged from that which now exists. Water Quality Effects The primary impact from mining on surface water quality at the Edna Mine was identified as potential salt loading of Trout Creek. Increased concentrations of total dissolved solids CTDS) in the stream were expected, based upon mass-balance calculations presented in the application. _~~_