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r <br />t <br />III IIIIIIIIIIIII III <br />sss <br />Cyprus Yampa Valley Coal Corporation <br />An Alfiliele of Cyprus Mmerels Camparry <br />29587 Routt County Road N27 <br />Oak Creek, CO 80467 <br />Phone (303) 8793800 <br />October 19, 1988 <br /> <br />OCT 2 ? 19E8 <br />Randall Price <br />Colorado Mined Land Reclamation Division <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203-2273 <br />Dear Randy: <br />,, <br />to the Fish Creek <br />In April of 1988, Twentymile Coal Company submitted the responses to <br />the Mid-Term letter of 13 October 1987. At that time, we had indicated a <br />review of the Pond E sizing would occur, using site specific spoil spring <br />discharge data. Our review of the adequacy of Pond E included examination <br />of the relevant data and calculations. <br />Within the July 1985 submittal of Exhibit 8, it had been indicated the <br />tributary area consisted of 24 disturbed acres and 11 undisturbed acres, and <br />the resulting weighted curve number was 82. Actually, the amount of <br />disturbed area is 22.8 acres and the undisturbed is 12.7 acres. Because of <br />this situation, the weighted curve number is 81. As a result, other <br />parameters of the pond sizing calculations change, and the final volume <br />requirement for runoff and sediment storage is 2.00 acre-feet, rather than <br />2.16 acre-feet. <br />When the tipple is operating, a maximum of 300 gallons per day would <br />enter the pond. This contribution is due to washdown of the tipple. Spoil <br />spring flow into the pond has been measured at a maximum of .02 cubic feet <br />per second. Adding the above amounts to the 2.00 acre-feet for runoff and <br />sediment storage, our calculations indicate Pond E must be designed to <br />accommodate 2.04 acre-feet of storage. <br />As-built certifications indicate Pond E has a storage of 2.19 <br />acre-feet. Therefore, the current capacity of the pond is sufficient to <br />handle surface runoff, sediment storage, operation discharge, and spoil <br />spring flow. The revised pages 2 through 10 of Exhibit 8 present the <br />modified calculations. Although the sediment storage requirement has <br />changed (.58 rather than .64 acre-feet), Twentymile Coal Company will not be <br />changing the elevation of the dewatering orifice. Itrs former elevation on <br />the riser pipe is slightly higher than the revised elevation; thus,the <br />current elevation will continue to serve the purpose of sufficient sediment <br />storage. <br />c~RUs <br />