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Because the situation at each mine will be unique to that mine, possible 1 streamflow depletion from induced al]uvial aquifer inflows will nave to be estimated on a case-by-case basis, However, it is suggested that, in most instances, any such inflows will probably be recycled to surface flows. It is recommended, therefore, that unless such inflows are consumptively used in the mine operation and not returned to surface flows, they should be eliminates from consideration as streamflow depletions. Deep aquifer inflows For consideration of streamflow effects, deep aquifers are those that are hydraulically isolated fran surficial aquifers, at least insofar as relatively snort-term effects are concerned, and whose recharge areas are relatively remote from the mine. Because inflows from such aqui fern are isolated from mine-area surface flows, any such inflows that are not consumptively used and that are pumped out of the mine and into stream channels can be considered augmentations to streamflow. Such streamflow augmentations are fairly common for underground mines. Estimates for the Eagle No. 9 mine (Coloraao) indicate streamflow augmentation of about 1,550 acre-feet/year for 20 years of mining activity. The Cottonwood Creek Basin (Utah) CHIA report estimates streamflow augmentation of about 2,900 acre- feet/year during mining. It is recommended that any such augmentations to streamflow derived from deep aquifer mine inflows be factored into the equation when overall mining effects on annual surface floes are estimated. Postmininq inflow to workings This is inflow to mine workings following shutdown df mining. Defending on wnether inflows are induced from surficial aquifers or are from deep aquifers, a depletion from streamflow may occur following mining. Estimates for the Eagle Plo. 9 mine are for inflows of 56 acre-feet/year for 3 years, derived from the alluvial aquifer. The Cottonwood Creek Cy [A report estimates an almost identical 55 acre-feet/year depletion from streamflow but is unclear as to the duration of the depletion. Considering that pumped mine outflows originating from deep aquifers and postmining inflows do not occur concurrently, it may not be possible to include these items in a single equation far estimating overall effects on endangered fisn. More definition of streamflow depletion effects on endangered species is needed from Fisn and Wildlife Service in this respect. Coal ttoisture Loss Tnis is loss of water adhering to coal as it is brougnt to the surface. An estimation of such losses at the Eagle No. 9 mine is 0.5 acre feet/year. Considering that this represents the loss for a Aroduction of 1.5 million tons/year, it is recommended that such effects, being generally insignificant, be eliminated from consideration as stresinflow eepletions. -5-