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'~, <br />not take into account the total area mined. The formula is as follows: <br />0.5 0.5 <br />Q = 4R (S Tb2/12) + (STHo2/4) * t <br />Q = discharge to the mains <br />R = rate of advancement of the mains <br />Sy = apparent specific yield <br />S storativity <br />T transmissivity <br />h = thickness of the coal <br />.'.o = initial piezometric height above the top of the coal seam <br />_ _ ~'^e since the initiation of the main <br />L = ,raxinum length of the main <br />Once the mine reaches maximum length length, the mine inflow is calculated <br />by the following equation: <br />Q = 4R (Sy Tb? + S ~)0.5 *(t0.5 _ t - L/R)0.5 t - L/R <br />The predicted inflows for the No. 5 and Plo. 9 mines are presented in Table <br />III-20. The input data is presented on Tables III-20a and 20b. This <br />method is probably most suitable for the present No. 9 mine inflow <br />because it is now only a simple set of mains with little panel development <br />having taken place. Far the longwall portion of the Empire Tract <br />(including Utah Tract extension) the lonawall development entries were <br />considered mains. <br />Jacob-Lohman Method - This method assumes that the mine is a large well <br />with constant drawdown and an inflow varying with time. The radius of the <br />"well" was estimated by calculating the radius of a circle with an area <br />equal to the area mined. The average drawdowns for the No. 5 and No. 9 <br />Mines were estimated to 400 and 600 feet respectively. This equation <br />assumes artesian conditions; however, it has been found to provide a <br />reasonable approximation of mine dewatering inflows where the initial <br />artesian head is large and the radius of the assumed well is large. The <br />(REV. 1/17/84) <br />III-72 <br />