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The 2004 re-survey was not completely definitive, as the gabion locations did not <br />align well with the original locations and the elevation datum had changed since the <br />original survey. However, the survey appears to indicate additional channel scour of <br />between 2 and 5 feet in a couple segments, notably a segment just downstream <br />from the upper gabion, and another segment in the vicinity of the lower gabion near <br />the confluence with East Salt Creek. The apparent areas of down-cutting indicated <br />on the survey were consistent with observations I made on an inspection of April <br />14, 2005. The Tower-most gabion was apparently dislodged and washed out by a <br />high flow event. Upper segments of the channel upstream of the upper gabion <br />location show no indication of down-cutting since the original survey, but in one <br />location along this upper segment, side-cutting erosion has advanced close to the <br />haul road (near the 15mph speed limit sign). <br />Based on the survey data and inspection observations, there does appear to have <br />been significant erosion subsequent to the 1997 gabion installation. Future high <br />flow events may result in additional channel scour and side-cutting erosion. <br />The permit indicates that corrective measures will be approved and implemented if <br />unacceptable erosion is occurring. "Unacceptable" is not defined, but segments of <br />the channel do not appear to be stable, and further erosion may be likely. Given the <br />nature of the channel and the magnitude of periodic high flow events, effective <br />stabilization using structural controls may be difficult. The most effective, long term <br />solution would appear to be installation of a properly sized culvert at the haul road <br />point of diversion to re-connect upper McClane Creek to its original lower segment. <br />Please submit a technical revision application addressing a plan for stabilization of <br />the diversion segment of lower McClane Creek. <br />Please provide a response to the two requests made in this letter, including a complete <br />technical revision application addressing stabilization of the lower McClane Creek diversion <br />segment by November 18, 2005. <br />Please contact me if you have questions, <br />Sincer y <br />Daniel T. Mathews <br />Environmental Protection Specialist <br />C: Denver File <br />Wafter Whitledge, Central Appalachia Mining, LLC <br />