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will continue for several thousand years at elevated salinity levels. Eagle • No, 5 and 6 will commence discharging in approximately 2020. A worst case analysis of salt loading would incorporate all mining-related impacts within the drainage with the exception of discharge from the flooded workings of Foidel Creek Mine. Salt loading calculations were performed at four nodes (discharge points) within the drainage; lower Fish Creek, Trout Creek below the confluence with Fish Creek, the Yampa River at Hayden and the Yampa River at Maybell, Computations were performed for both a flood irrigation and a sub-irrigation scenario, utilizing average low historical flows. The sub-irrigation scenario assumed that water would recharge the alluvial aquifers in the spring during peak flows. When available, well records from those periods were examined to determine the level of increase in the alluvial water level during recharge and a weighted average was computed between the volume and quantity of recharge and the volume and quality in the well, (In cases where well level records were not available, an example case of 2.5' of recharge to 6, 9' of existing well volume was used.) The flood irrigation case utilized the period between June 1 and August 31. The parameter of Total Dissolved Solids (TDS) was used to estimate the salinity, and was converted to electrical conductivity (EC) following the calculations. Twentymile Coal Company provided an estimate of the relationship of TDS to EC as TDS = 0.73 EC. • (TDS x Qex) + (TDSs x Qs ) + (TDSmi x Qmi) _ ex + sp + i TDS = Total Dissolved Solids sp Aquifer Levels Q = Discharge mi = Mine Inflow Levels ex = Existing Low Flow Levels Backfill spoils discharge predictions were also based on a similar weighted average calculation, Simplistic equations relating observed discharges from the eastern half of the Eckman Park backfill with acreages of reclaimed spoils follow: Q peak = 2.985 x 10-3 x A Q mean Sept. -Feb. flow = 1,594 x 10-4 x A Q = Discharge A = Acreage These equations represent an analysis of the worst discharges observed to date on the Cyprus Western Coal holdings, but may not be representative for all hydrologic conditions. Peak spoils discharges occur during the recharge period (April and May) for alluvial wells and were used to predicting impacts to sub-irrigated areas. Mean low flow discharges represent the average flow between June and August. Spoils flow during the period of June 1 and August 31 seemed best represented • -44- .r