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p-4 <br />III IIIIIIIIIIIII III <br />999 <br />PEABODY COAL COMPANY <br />Wsratsrn Dlvlslon <br />April 24, 1991 <br />Mr. Dan Mathews <br />Colorado Mined Land <br />1313 Sherman Street, <br />Denver, CO 80203 <br />Reclamation Division <br />Room 215 <br />RE: Permit C-82-057, Seneca II-W Mine, TR 12 <br />Dear Mr. Mathews: <br />1300 South Vale <br />Fla9stafl, Arizona 86001 <br />(602) 774-5253 <br />RECEIVE <br />APR 2 9 1991 <br />Mined Land <br />Reclamation Division <br />Peabody Coal Company has reviewed the Division's letter of April 17, 1991, which <br />contained comments on Technical Revision 12. The following are Peabody's <br />responses to these comments: <br />Peabody does not intend to riprap all portions of the <br />ditch in which the slope is 5% to 10%. Only the areas <br />of TAHRD-9 in this slope range which are exhibiting <br />severe erosion will be riprapped to control erosion. <br />All portions of the ditch greater than 10% will be <br />properly protected from erosion with riprap. <br />Therefore, Exhibit 12-9-4 does not show the location of <br />the riprap in the portion of the ditch between 5% to <br />10% slope. These locations will depend upon field <br />conditions of the ditch. Table 12-5A (page 12-29b) has <br />been revised to correct the error in TAHRD-9R. <br />TAHRD-9A was designed as a triangular ditch section to <br />ensure that the ditch would handle the runoff and be <br />stable. The final shape and configuration of the <br />riprapped ditch will depend on field conditions and <br />type of equipment used. The ditch section will most <br />likely resemble a trapezoidal shape with a 2 or 3 foot <br />bottom width. This constructed shape will have the <br />capacity to handle more runoff. The ditch bottom will <br />be properly protected to ensure that no undercutting of <br />the riprap occurs. <br />Insertion instructions are attached for the enclosed text revision. If you or <br />your staff have any questions concerning the enclosed information, please <br />contact me at your earliest convenience. <br />Sincerely, <br />~~ ~- <br />Gary W. Wendt <br />Supervisor, Permits <br />GWW/pf <br />Attachment <br />