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salinity levels. Eagle No. 5 and 6 will commence discharging in approximately <br />2020. A worst case analysis of salt loading would incorporate all <br />mining-related impacts within the drainage with the exception of discharge <br />from the flooded workings of Foidel Creek Pine. <br />Salt loading calculations were performed at four nodes (discharge points) <br />within the drainage; lower Fish Creek, Trout Creek below the confluence with <br />Fish Creek, the Yampa River at Hayden and the Yampa River at Maybell. <br />Computations were performed for both a flood irrigation and a sub-irrigation <br />scenario, utilizing average low historical flows. <br />The sub-irrigation scenario assumed that water would recharge the alluvial <br />aquifers in the spring during peak flows. When available, well records from <br />those periods were examined to determine the level of increase in the alluvial <br />water level during recharge and a weighted average was computed between the <br />volume and quantity of recharge and the volume and quality in the well. (In <br />cases where well level records were not available, an example case of 2.5' of <br />recharge to 6.9' of existing well volume was used.) The flood irrigation case <br />utilized the period between June 1 and August 31. <br />The parameter of Total Dissolved Solids (TDS) was used to estimate the <br />salinity, and was converted to electrical conductivity (EC) following the <br />calculations. Twentymile Coal Company provided an estimate of the <br />relationship of TDS to EC as TDS = 0.73 EC, within their application for the <br />Foidel Creek Mine. <br />(TDS x Qex) + (TDSsp x Qsp) + (TDSmi x Qmi) _ <br />ex + sp + i <br />TDS = Total Dissolved Solids sp = Aquifer Levels <br />Q = Discharge mi = Mine Inflow Levels <br />ex = Existing Low Flow Levels <br />Backfill spoils discharge predictions were also based on a similar weighted <br />average calculation. Simplistic equations relating observed discharges from <br />the eastern half of the Eckman Park backfill with acreages of reclaimed spoils <br />follow: <br />Q peak = 2.985 x 10-3 x A <br />Q mean low flow = 1.594 x 10-4 x A <br />Q = Discharge <br />A = Acreage <br />These equations represent an analysis of the worst discharges observed to date <br />on the Cyprus Western Coal holdings, but may not be representative for all <br />hydrologic conditions. <br />Peak spoils discharges occur during the recharge period (April and May) for <br />alluvial wells and ~~~ere used in predicting impacts to sub-irrigated areas. <br />Piean low flow discharges represent the average flow between June and August. <br />Spoils flow during the period of June 1 and August 31 seemed best represented <br />-24- <br />