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Mr. Dan )\iathews <br />April 11, 1991 <br />Page 2 <br />b) in areas where erosion is more severe <br />and the slopes are steeper (slope 5%- <br />8%), riprap will be properly placed in <br />the bottom of the trapezoidal ditch. <br />Design parameters for the riprap <br />sections of TAHRD-9R are presented in <br />Appendix 12-7, Addendum 2. <br />c) 1n the steepest areas (slopes over ]0°l0), <br />a riprapped triangular downdrain has <br />been designed (TAHRD-9A) and will be <br />constructed. Exhibits 7-10A and 12-9-4 <br />depict the location of TAHRD-9A.The <br />riprap in the do~vndrain will be properly <br />installed to ensure no flow undercuts or <br />bypasses the rocks. <br />All remedial work will be implemented and completed, weather <br />permitting, by May 30, ]991 assuming TR 12 is approved promptly. <br />Please find enclosed the insertion instructions, application form, and <br />proposed public notice fur this TR. Peabody requests the Division's <br />expeditious review of this TR. Please contact me or Fred Fest if you <br />or your staff have any questions or stould need additional <br />information. <br />Sincerely, <br />~~ ~. ~,/. <br />Gary W. Wendt <br />Supervisor, Permits <br />jdc <br />Enclosure(s) <br />