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10 <br />COAL <br />COMPANY ¢� <br />PEOPLE• PRODUCTIOT& .El'tif' <br />Colowyo's Response: <br />Probably the best justification for reduction in the current curve numbers, especially for <br />those associated with reclamation areas > three years and older is the performance of <br />the ponds below areas that have received Phase III bond release, namely Gulch A, <br />Streeter, and the West Pit Pond. With the exception of inflow from runoff caused by <br />snowmelt or rain over frozen ground, these three ponds normally receive no inflow from <br />surface runoff generated by storm events in recent history. All of these structures were <br />designed and constructed utilizing much lower curve numbers than those currently in <br />force today or those proposed in the TR -95 submittal. <br />Division Comment (Fourth Adequacy) <br />The vegetation growth on areas that have been Phase III released (where vegetation <br />is at least 10 years old) could be vastly different than areas with three years of <br />growth. Does Colowyo have any data showing that reclamation areas that are <br />approximately three years old produce little runoff from a 10 year or greater storm? <br />Colowyo's Response (Fourth Adequacy): <br />As stated previously, Colowyo does not have a mechanism for directly measuring inflow <br />into ponds during storm events. In most cases at Colowyo, the majority of reclaimed <br />acres reporting to sediment ponds are greater than three years post reclamation. <br />COMMENT #4 <br />My apologies for not being more clear when I repeated the original comment in my July <br />2, 2012 letter. What I meant to say is that, in the Division's opinion, Colowyo did not <br />answer the question. Please describe how each of the values in the sediment loading <br />section of Table 6 is calculated, including the sources of information. This should be <br />done in a very direct manner, possibly using an example. This issue has also been briefly <br />discussed with Colowyo staff (Kurt Blunt) at the mine's administration office. <br />Colowyo's Response: <br />Colowyo has included the previously approved version of Table 6 in this package and is <br />no longer seeking to modify it through this process. <br />Division Comment (Fourth Adequacy) <br />This response is adequate. <br />GENERAL COMMENT <br />It is very important to consider what is happening on the ground. The SEDCAD models <br />are valuable information, but the Division is also concerned about the stability of <br />A mining property of Western Fuels - Colorado, A Limited Liability Company <br />