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DATE: May 4, 2005 TO: Sandy Brown and Ji Burnell FROM: Dan Mathews RE: 2004 AHR for McClane and Unger Canyon Mines Permit No. C-80-004 (McClane) and C-81-020 (Munger) I have conducted a preliminary review of the 2004 AHR for McClane and Munger Canyon Mines. I need to request Jim's assistance, to conduct the PHC review. The report is largely consistent with last year's report, with the exception that the report included a profile survey along the lower segment of McClane Creek that was diverted when the McClane Canyon road was constructed (pre-8/3/77). I had requested the profile survey during the recent mid-term review, based on a commitment in Appendix "M" of the permit, which indicates that the channel would be monitored for evidence of erosion. McClane McClane Creek Temporary Diversion The diverted segment is relatively straight, and is incised/entrenched. Headword migration of the incision seems to have been prevented by sandstone outcrops a short distance down- gradient from the point of diversion, and I have not noticed apparent changes along the upper portion of the diverted segment since I initially became aware of the feature in 1996 (shortly after I began doing inspections at McClane). The survey appears to show additional incision of up to 5 feet along one segment in the middle portion of the reach, and a second segment at the lower end, near the confluence with East Salt Creek. I checked the entire reach during my April 14, 2005 inspection, documented my observations and took numerous photographs. My intent was to compare my observations and photos against the observations I had recorded in an inspection report of May 20, 1996. Unfortunately, in the imaged version of the subject inspection report, one or more pages are missing trom the Section III narrative, in which I described the observations made at that time. I will try to track down the missing pages, and complete my evaluation prior to preparation of our final AHR review letter. Permit Appendix "M" addresses the diversion segment, and indicates that the channel would be monitored, and "if unacceptable erosion is occurring, corrective measures will be approved and implemented". Upon final reclamation, the road is to be eliminated, and the creek is to be restored to its original flow path, with the diverted entrenched segment to be revegetated. My preliminary assessment, based on the surveyed channel profile, and the observations made during my recent inspection, is that down-cutting and side-cutting erosion has occurred along several segments of the channel, arid additional erosion is likely to occur during periodic, infrequent flood events in future years. I believe the most prudent approach to prevent future incision and/or widening of the diversion channel, would be to install large