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+ ++ Q <br />where Q = Areal recharge rate <br />K = Permeability of the spoil <br />S = Pit slope <br />x,y,t = Cartesian coordinates and time <br />Making certain idealizing assumptions, the hydraulics of groundwater flow within <br />the spoil can be described by the following mathematical model. <br />(y+sx) d2y + C R )2 + S jZ + ,Q = <br />&2x2 6y dx K dt <br />The solution of this model gives the development of the groundwater mound in time <br />iwithin the spoil and its dimensions. Assuming a K value of 50 gpd/ft2 for <br />undisturbed ground, the maximum potential height of the water table is three feet <br />above the pit crest elevation. The water table is not horizontal within the <br />recontoured spoil, but is parabolic. <br />It must be noted, however, that each successive cut within a pit will likely <br />have <br />a different crest elevation at the northern end. This is the result of changes <br />in <br />topography and varying coal recovery conditions from cut to cut that influence <br />the <br />maximum practical depth of each cut. Map M47a shows the successive pit cuts in <br />Ashmore, Derringer, and Enfield Pits where utility wastes may be disposed. <br />This <br />map shows the variation in the locations of the north ends of the cuts. The <br />low- <br />est crest elevation for any one cut in a series of adjacent cuts will control <br />the <br />maximum potential water table elevation in all the cuts that can drain to <br />it. <br />This will hereafter be referred to as the "critical pit crest elevation". <br />Map <br />M47a shows the potential areal extent of reestablished spoils aquifers for <br />each <br />pit as projected from the critical pit crest elevations. All utility wastes <br />will <br />be disposed at least ten feet above the critical pit crest elevation. For <br />all <br />7-8-82 4-98a <br />2 1992 <br />$EP <br />