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Mountain Coal Company Exhibit 67 <br />West Elk Mine Windy Gap Process <br />0 Pond Eva oration <br />An estimate of 45 inches per year for Class A pan evaporation was obtained from <br />USWB TP 37, 1959. A pan coefficient of 0.75 was used to obtain an annual pond <br />evaporation estimate of 33.8 inches per year. Since all precipitation reaching the <br />ponds would be available for release or evaporation, the net evaporation is 13.7 <br />inches per year (using an annual precipitation of 20.1 inches). Consequently, for <br />a total pond surface area of 5.9 acres, the annual evaporation loss is 8.5 acre-feet. <br />Surface area of the ponds are as follows: <br />MB-1 1.5 ac. <br />MB-2R 1.5 ac. <br />MB-3 0.25 ac. <br />MB-4 0.25 ac. <br />MB-5 0.5 ac. <br />SG-1 0.5 ac. <br />RPE Pond 1.4 ac. <br />Miscellaneous Water Use <br />Miscellaneous water use includes surface road dust suppression, potable water, <br />and equipment wash water. Much of the use associated with the above activities <br />have return flows via WEM's WWTP. Using the data from 1996, the potable <br />water usage was calculated to be 15.9 acre-feet. Also, WEM is estimating other <br />miscellaneous water use to be an additional 11.2 acre-feet. Therefore, the total <br />miscellaneous water use is approximately 27.1 acre-feet. <br />Return Flows <br />Return flows to the North Fork are attributed to discharges of treated effluent from <br />WEM's WWTP and water circulated, then discharged from the mine. Using the 1996 <br />data supplied in Table 75, Projected Wastewater Plant Discharges of WEM's Mining and <br />Reclamation Plan, 15.3 acre-feet will be returned to the North Fork every year from the <br />WWTP. Utilizing the 1994 Annual Hydrology Report figure (as well as an average of <br />the past three years), 61.7 acre-feet of water was pumped from the mine and returned to <br />the North Fork. Approximately 8.7 acre-feet of that amount is contributed through mine <br />inflows, as described below. The remainder, 53 acre-feet, is water recovered in the mine <br />after circulating through the mining sections. This water is pumped out of the mine, <br />treated if necessary and discharged. <br />• <br />Exhibit 67-2 Revised March 2005 PR11; Rev. January 2006; Rev. March 2006