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Page 3 of 4 <br />resulting from the observed pond condition reflecting complete plugging of the primary and <br />secondary outlets, and partial plugging of the emergency spillway. It is reasonable to conclude <br />that the actual storm intensity above Prospect Pond was locally greater than what was captured <br />by the precipitation monitors. <br />Division Comment (Final) <br />No further response is required. <br />COMMENT #3 <br />The condition of Colowyo's mine site will change drastically as reclamation progresses, and <br />compliance with water quality regulations in the past is not an assurance that future conditions at <br />the site will also result in compliance. Therefore, one cannot say that past compliance is <br />justification for lowering curve numbers. <br />Colowyo's Response: <br />Probably the best justification for reduction in the current curve numbers, especially for those <br />associated with reclamation areas > three years and older is the performance of the ponds <br />below areas that have received Phase III bond release, namely Gulch A, Streeter, and the West <br />Pit Pond. With the exception of inflow from runoff caused by snowmelt or rain over frozen <br />ground, these three ponds normally receive no inflow from surface runoff generated by storm <br />events in recent history. All of these structures were designed and constructed utilizing much <br />lower curve numbers than those currently in force today or those proposed in the TR -95 <br />submittal. <br />Division Comment (Fourth Adequacy) <br />The vegetation growth on areas that have been Phase III released (where vegetation is at <br />least 10 years old) could be vastly different than areas with three years of growth. Does <br />Colowyo have any data showing that reclamation areas that are approximately three years old <br />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 into <br />ponds during storm events. In most cases at Colowyo, the majority of reclaimed acres reporting <br />to sediment ponds are greater than three years post reclamation. <br />Division Comment (Final) <br />The Division still contends that Colowyo is erroneously trying to equate runoff from <br />reclaimed areas that have three growing seasons to runoff from areas that have 10 growing <br />seasons. However, this point is not essential to the overall issues raised with this revision <br />and previous adequacy letters. <br />No further response is required. <br />COMMENT #4 <br />Previous response was adequate. <br />