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-- ~ - -2- i <br />.: . <br />Following submission of the above information, the Division should be <br />able to make a determination on the presence of alluvial valley floors. <br />I can forsee no additional information needs at this time. However, if <br />Powderhorn Coal Company concedes that all areas cahich meet the geomorphic <br />criteria, water availability criteria, and size criteria are alluvial <br />valley floors the time to make the required finding will be much less. <br />In addition, this should have no effect on the permit requirements. <br />Powderhorn stated that considering the empirical nature of the peak t'low <br />calculation for Coal Creek and that extra freeboard was available, <br />the capacity of the Cameo 111 pipe arches may be considered adequate. <br />The Divisions calculations show that the pipe arches are still approximately <br />ten percent undersized. Also, in lieu of actual flow data from Coal Creek, <br />an empirical method must be used to determine the peak flow. Therefore, <br />Powderhorm must submit evidence that the culverts will pass the 20-year, <br />24-hour peak flow. One possible method would be to install or construct <br />improved inlets to increase the culvert capacity. <br />If you have any questions, please call. <br />Si cerely~ <br />, <br />erron ~ <br />ec amation Specialist <br />JH:ep <br />cc: B. Tate <br />