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revious estimates were higher because they included assumptions that faults would contribute significant inflows. <br />The mine has crossed a number of faults, including two significant fault zones. Fault inflows have never exceeded <br />25 gpm in the short-term (one [o two weeks), and have never exceeded 10 gpm average over a year. <br />The accuracy of these calculations depends on the quality of the input data. The most important input parameter is <br />hydraulic conductivity. The results of the calculations depend, to a large degree, on the validity of the hydraulic <br />conductivity value for a large section of the aquifer. <br />Limitations of this method of calculation for a large mine with variable hydrogeologic conditions due to the <br />lenticular character of the sandstone is in defining an average hydraulic conductivity representing all sections of the <br />mine. Results of the calculations, therefore, express the general trends in inflow and the values should be <br />considered very approximate. The calculated values are not specific for certain smaller sections of the mine and <br />express an average inflow per year. <br />NMD (Panels 12 Right through 16 Right)(PR 99-OS) <br />Probable Hydrologic Consequences <br />The probably hydrologic consequences will focus on the panels added in the NMD (12 Right through 16 Right). [t <br />is planned to use as much of the water that is produced underground in the spray system for dust control. The <br />remainder of the water will be pumped to the surface and discharged in with Fish or Foidel Creeks. It is not <br />planned to pump above historic levels. Therefore, the prior impacts should be applicable to the NMD. <br />Impacts to Surface Water <br />It is anticipated that Fish Creek will respond similarly to the response observed in Foidel Creek, which overlies the <br />7, 8, and 9 Right panels. The response observed is for a pool to form in the subsidence trough for the respective <br />panel. The extent of the pool will be dictated by the bank height. Typically, the subsidence trough lessens in <br />magnitude as you move from the centerline of the panel until it reaches zero at the angle of draw limit. As was <br />evidenced in the EMD, i.e., no head cutting at gateroads,the formation of the pool decreases erosional potential <br />within the subsided segment of the stream. <br />The pre and post mining gradients of Fish Creek is presented on Table 4 of Exhibit 7e-3. With the formation of the <br />pools over panels 13 Right through 16 Right, TCC is not projecting any erosional problems in the stream channel <br />using the historic flow data for Fish Creek, and the visual observations along Foidel Creek which overlaid Panels 7 <br />through 9 Right. These observations did not detect any erosional problems caused by TCC's mining operation <br />A potential outcome from creation of the small pools is an increase in water temperature during the summer <br />months. A look at the historic data for the months of January through September indicates that the segment of Fish <br />Creek to be subsided during this five-year term already exhibits elevated temperatures during this period. The <br />historic data is presented in Table 71, Period of Record Average Temperatures, dated January through September. <br />Stations 16 and 302 are upstream of the subsided area and will not be impacted by the proposed mining in the <br />Northern Mining District. As reflected in the data, these stations record the coolest temperatures during the period <br />of intent, although both stations reflect temperatures of greater then 19 ° Celsius during July. Station 1002 is <br />located over panel 13 Right and will be the only station impacted by the mining activities. As noted on Table 71, <br />average water temperature range from 16.5° C to 19.2 ° C during June through August and 14.5 ° C during <br />September. The temperatures during January through August are not conducive form maintaining acold-water <br />fishery. Likewise, [he water temperatures for Stations 27A 1003 reflect higher temperatures than Station 1002. <br />This would be considered normal given their location on lower Fish Creek. Again, the temperatures are not <br />conducive for maintaining acold-water fishery. Given the historic warming of the creek during the summer <br />months, no significant impacts are anticipated to result from the undermining and subsiding of the various segments <br />L of Fish Creek. Likewise, the TDS concentrations are low enough at this point to believe that there will be no <br />impacts to TDS concentrations in these pools. <br />APPROl/~P3 JllN 2 g. 2000 <br />PR 99-OS 2.05-171.6 8/27/99 <br />