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Q <br />~~ a <br />~` 6x + ~ dx <br />dx <br />4°dQ Q Q+dQ <br />VdX K <br />S <br />1 dx <br />where Q = Areal recharge care <br />K = Permeability of the spoii <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 />dpxp 6y dx K dt <br />The solution of this model gives the development of the groundwater mound in time <br />~ i 'within the spoil and its dimensions. Assuming a K value of 50 gpd/ft2 for <br />undisturbed ground, the maximum potential height o_` 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 have <br /> a different crest elevation at the norchern end. This is the result of changes in <br /> topography and varying coal recovery conditions from cut to cut that influence the <br /> maximum practical depth of each cut. Map M47a shows the successive pit cut s in <br /> Ashmore, Derringer, and Enfield Pits where utility wastes may be disposed. This <br /> map shows the variation in the locations of the north ends of [he cuts. The low- <br /> est crest elevation for any one cut in a series of adjacent cuts will control the <br /> maximum potential water table elevation in all the cuts that can drain to it. <br /> This will hereafter be referred to as the "critical pit crest elevation". Map <br /> M47a shows the potential areal extent of reestablished spoils aquifers for each <br /> pit as projected from the critical pit crest elevations. All utility wastes will <br /> be disposed at least ten feet above the critical pit crest elevation. For all <br />' ~ 7-8-82 4-98a <br /> 2 1962 <br /> $EP <br />