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Mountain Coal Company Exhibit 67 <br />West Elk Mine Windy Gap Process <br />n <br />U <br /> <br />As discussed in the 1994 Annual Hydrology Report, 8.7 acre-feet of water was measured <br />as mine water inflow. The natural mine water inflow is not proportional to the <br />production rate, but is affected by the areal extent mined and the geologic conditions. <br />Therefore, the 1994 data will be used for the entire term of permit. WEM believes that <br />this water is a valid contribution to the upper Colorado River basin because the water <br />would have remained isolated in perched confined aquifers if mining had not occurred. <br />MCC is currently experiencing net increases of water discharged to the N.F. of the <br />Gunnison River of+306 acre-feet (2003 WY). As more information and data have been <br />obtained (since TR-79, April 1997) regarding the mine water balance, Exhibit 67 is very <br />conservative because no depletions have been experienced since 1998. <br />No depletions have been experienced as a result of mining in the Box Canyon Federal <br />Lease COC-56447 (PR08). No depletions are anticipated as a result of mining in either <br />the South of the Divide Federal Lease C-1362 (PR10) or in the West Flatiron Federal <br />Lease COC-67011 (PR-11). <br />Net Depletion <br />Depletion for the North Fork 170.2 acre-feet/year <br />Return Flow to the North Fork 77.3 acre-feet/year <br />Contributions to the North Fork 8.7 acre-feet/year <br />NET DEPLETION 84.2 acre-feet/year <br />• <br />EXhlblt 67-3 Revised Sept. /995 TR77; Revised Apr. 1997 TR 79, Revised March 1005 PRII <br />~ iy.u ~ <br />