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Mr. Rick Mills -2- was one depicted on the original mapping? depicted on the new mapping and the need be addressed. Also, it would be helpful number designations were included for all depicted on Map 48-A. May 4, 1987 If so, it should be for stabilization should if drainage channel of the channels A comparison of the channel repair locations map with Map 48-A reveals a number of discrepancies. Most notably, the former map depicts two closed basins in the Area 9/10 Swale feature The discrepancy should be clarified and the mapping which is incorrect should be corrected. As you are aware, closed basins would not be approvable. e. The revised topography in Area 5IE is proposed in part (as presented in the April 16th meeting) to divert drainage from the present pit area away from drainage 9/10-2 (5IE). In doing so, an extreme meander has been placed in the channel on a relatively flat reach of the channel and drainage basin. This meander has the potential to be a point of instability in the channel in that overtopping of the channel could lead to the flow seeking a new channel. This possibility is further enhanced by the flat side slopes on the drainage basin in this area: The Division believes the radius of curvature of this meander should be greatly increased or the meander should be eliminated. f. Several drainages proposed in the post-mining topography, as depicted in the shaded portions of Map 48-A, show little to no relief on the side slopes of the drainage basins. As required by Rule 4.05,4(2)(a) "the floodplain shall be designed and constructed to remain stable" and from Rule 4.05.4(2)(b) "shall be adeouate to pass safely the peak runoff of a 100 year, 24-hour precipitation event for permanent diversions." An analysis must be submitted demonstrating that the flood plains are capable of carrying a 100-year, 24-hour precipitation event. An alternative to performing this engineering analysis would be to revise the post-mining landscape to create better defined drainage basins with more relief between drainage side boundaries and the channel. Channel design drawings will need to be certified by a P.E. 3. Six stock ponds are proposed in the amended application. Design information demonstrating compliance with the permanent impoundment criteria of Rule 4.05.9 will need to be submitted. State Engineer design specifications are included-as Attachment 1. 4. No reclamation cost calculations reflecting the amended plan were included in the responses. The Division has estimated the reclamation cost based on the amended plan, Equipment costs were based on the same references and assumptions as used previously for