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The applicant used two mathematical models to obtain a projected combined <br />mine inflow rate and drawdown cone within the Wadge coal-overburden <br />aquifer. These two models were the GROUND WATER model, a finite <br />difference, two-dimensional digital model, and a Line-Sink model. The <br />GROUND WATER model was developed by Colorado State University to predict <br />steady-state dewatering of an aquifer, while the Line-Sink model <br />presented in McWhorter and Sunada (1977) was used to predict the <br />additional inflows resulting from the dewatering of two fault zones. A <br />description of the modeling can be found in Exhibit 39 and Table 60 of <br />the permit application. <br />The input data for the 1983 GROUND WATER model produced a map of the <br />existing potentiometric surface which showed an upwelling of the ground <br />water surface two miles northwest of the Foidel Creek portals. The wells <br />used to produce this map were re-evaluated during the permitting process, <br />and it was found that some well data from that area was inappropriately <br />interpreted. The applicant presented a new map (Map 13, revised 7/86) <br />exhibiting a potentiometric surface dipping to the northeast. <br />Mine inflow waters to the Foidel Creek Mine are expected to be derived <br />from lateral dewatering of the Wadge overburden sandstone and vertical <br />migration from the Trout Creek sandstone where faults intersect the mine <br />workings. Fault-related inflows during the first two years of operation <br />were far less than originally projected for the mine while overburden <br />inflows were higher. This information was used to adjust the ground <br />water model and the McWhorter Line-Sink Model. The resulting discharge <br />rates and extent of the drawdowns from the two models were added together <br />to obtain a total maximum predicted mine inflow of 310 gallons per minute <br />(92 gpm from the aquifer and 218 gpm from the three faults) and to <br />develop a map of the total projected water level decline in the affected <br />aquifer (see Figure 5). Maximum mine inflows are predicted in 1988 when <br />the mine intercepts Fault No. 8 (Exhibit 33). TABLE 1 summarizes the <br />source of mine inflows to the mine. <br />TABLE 1: Statistical Analysis of Sources of Mine Water Inflows <br />Flow Rate Wadge Fault- Total Inflow* <br /> Overburden Related <br /> Flows Flows <br /> (gpm) (gpm) (gpm) (cfs) <br />Low 13.9 0 45.9 0.10 <br />Nigh 198.6 218.2 310.2 0.69 <br />Average 116.5 48.2 164.7 0.377 <br />*Fault-related inflow values and Wadge overburden inflows values do not occur <br />in the same years and consequently total inflows do not reflect the sum of <br />each. <br />-14- <br />