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PQ_y iii niiiiiiiiiii iii • PEABODY COAL COMPANY W~~brn Dlvblon 1300 Sou~ft Vale Flagatalt, Arizona 66001 1602) 774-5253 December 21, 1989 • _~ - Mr. Carl Mount \ ~~,r~ Colorado Mined Land Reclamation Division s ~gB9 1313 Sherman Street pE~ 2 215 Centennial Building INE,p1~`Npig10~1 Denver, CO 80203 M N pIV ~EG~MAS10 RE: Seneca II-W, Permit C-82-057, Technical Revision No. 5, Stipulation No. 15 Dear Mr. Mount: This submittal responds to the above referenced stipulation which was attached to the permit as a part of the approval of Technical Revision No. 5, including culvert and ditch corrections and a recalculation of reclamation costs. The following discussion addresses each of these items. Culverts Culvert HRC-B7 was checked and redesigned. Culverts HRC-64 and HRC-85 have been redesigned. Tables 12-4 and 12-1-1 have been revised and recalculated and are included in Appendix 12-1. Culvert HRC-66 was redesigned with the correct drainage area. Both HRC-86 and HRC-B4 were designed for the 10 year, 24 hour storm in accordance with the regulations. Table 12-4 and 12-1-1 have been revised to show the revised calculations. Appendix 12-1 was revised to include HRC-B6. Also, an error in the drainage area was found for HRC-A8 and the runoff was recalculated. The size of HRC-A8 was not changed. • Ditches Exhibit 7-10 has been revised to address ditch drainage areas. A majority of the ditch watershed areas are the same as the corresponding culvert watershed area. Where there is a difference in drainage areas a ditch drainage boundary was shown on Exhibit 7-10. All ditches were recalculated using SEDCAD+ grid Tables 12-5 and 12-3-1 were revised. Calculations for all ditches are included in Appendix 12-3.