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Coa] Processing Consumption <br />1 Tnis includes coal-preparation plant use for coal washing, etc. <br />Price River Coal Co., Utah, for example, estimates maximum annual <br />consumption to be 398 acre-feet for its preparation plant facility. <br />Because the source of this water is a direct diversion from the Price <br />River, the consumption is a direct depletion from streamflow. However, <br />actual coal production at the mine averages about 25 percent of capacity <br />per year, reducing actual consumption accordingly. <br />Because coal-preparation plants require reliable water supplies, the source <br />of such supplies will proabably be streamflow diversions or high-yield <br />alluvial wells--both of which can generally be considered direct depletions <br />from streamflow. Because of the nature of the supply and the relatively <br />large quantities of water needed, it is recommended that this source of <br />consumption be estimated for all such coal-processing facilities. However, <br />because consumption for such uses can be closely estimated, actual rather <br />than maximum potential use should be the basis for the streamflow depletion <br />estimate. <br />Sediment pond evaporation <br />This is a loss from stored water generally derived from interception of <br />surface runoff. Most such storage represents only a temporary detention, <br />due Lo the regulatory dewatering requirement. The temporary nature of <br />sediment pond storage is recognized, for instance, by the State of Wyoming, <br />which 155U25 permits in such CdSes only for sedimentation-Control pU rpoSeS. <br />These permits require that the ponds be evacuated when discharge standards <br />are met. In instances where sediment pond water is consumptively used, <br />sucn as for dust control, irrigation, etc., such use is specifically <br />autnorized in the permits. <br />For underground mines, the area of surface disturbance is generally small, <br />requiring only minimal pond capacities. For instance, the total surface <br />area of all Price River Coal Co. sediment ponds at maximum capacity is <br />about 2.0 acres. A maximum possible annual evaporation from these ponds is <br />less than 7.U acre-feel, based on 40 inches annual evaporation. Because of <br />the small pond surface areas involved and the intermittent nature of water <br />storage, it is recommended that evaporation from sedimentation ponds at <br />underground mines be eliminated from consideration in estimating streamflow <br />depletions. However, if significant mine pumpage is ,,^etained in ponds, <br />then the evaporation estimate should consider average pond surface areas <br />resulting from such sustained inflows if the source of mine water is an <br />abstraction from alluvial aquifers. <br />Subsidence effects on springs and seeps <br />The principal effect of subsidence is disruption of bedrock aquifers which <br />supply springs and seep f]ows. The effects of subsidence may be to eitner <br />diminish or, in some instances, to augment flow. Interrupted or diminished <br />flow may result from alteration of discharge points or yields witn cnanges <br />in potentiometric gradients and heads or short-circuiting of grounc-..ater <br />flow patns from aquifer to aquifer nitn cnanges in fault trace transmissi- <br />vities, for example. Augmented flow could be induced by increasel rates of <br />infiltration as a resul± of surface fracturing and depression interception <br />of surface flows. <br />-3- <br />