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Technical Revision Application to Permit C-044-81; <br />• Access to E Seam <br />February 14, 1986 <br />Page 2 <br />the development activities. These issues, a description of the operations <br />planned, and the 'prnnosed public notice which will be published in <br />accordance with Rule 2.08.4 (5)(6) are addressed within the enclosed <br />Technical Revision application. <br />As a result of the E Seam access work, Empire Energy will be accumulating <br />data for determining the economics and mining engineering aspects of <br />further development of the E Seam coal in our No. 6 Mine. Preliminary <br />mine plans have been established. Based upon these plans, some estimates <br />of possible hydrologic impacts have been prepared. <br />Inflow to the No. 6 Mine was estimated using the Jacob-Lohman Constant <br />Drawdown Equation and the Theim Steady State Equation. These equations <br />are included in the attached technical revision. During the first five <br />years of mining, almost all of the No. 6 Mine workings will be located <br />directly under old workings of the No. 5 Mine. The No. 5 Mine will be <br />dewatered at least through the first 10 years of mining within the No. 6 <br />Mine. Due to these conditions, it was, therefore, assumed that all inflow <br />to the No. 6 Mine through year 5 will come from dewatering the rock <br />between the No. 6 and No. 5 Mines - a static head of approximately 100 <br />• feet. <br />Beginning in year 6 of mining, the No. 6 Mine will extend beyond the No. 5 <br />Mine. The head was assumed to be 700 to 800 feet. This is a very <br />conservative assumption because the previous dewatering of the No. 5 and <br />No. 6 Mines will have reduced this head. <br />Based upon these assumptions, the inflow to the E Seam mine would be <br />approximately 50 to 100 gpm for year 1 to 5 and 500 to 1,220 gpm for years <br />6 to 10. Because the No. 5 Mine will be dewatered during this time, the <br />outflows from the E Seam mine will be in-addition-to the discharge from <br />the No. 5 Mine. <br />The mining of the E Seam should cause some additional drawdowns in <br />adjacent aquifers. Since much of the drawdown in the aquifers appears to <br />be related to faulting, the amount of the drawdown cannot be quantified. <br />However, no significant faults will be encountered in the area to be mined <br />under the existing No. 5 Mine workings and no faults of the type <br />encountered in the 2 West area of the No. 5 mine are known to exist in the <br />area to be mined in the E Seam. <br />The additional amount of stream depletion is expected to be relatively <br />small. The worst case estimate of stream depletion for the No. 5 Mine is <br />180 gpm. The present preliminary mine plan for the ~E Seam has no mining <br />under or west of the Williams Fork and Yampa Rivers. Because of this the <br />. estimated maximum stream depletion for the E Seam mine would be no more <br />than one-half of that calculated for the No. 5 Mine. The combined worst <br />case stream depletion of 270 gpm (0.6 cfs) for the two mines would, <br />