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stockpond and Culvert YA-1. Silt fence was installed along the toe of the <br />fill to prevent any additional sloughing of material into the waterway. A <br />field survey of this entire area was conducted on April 17, 1997 to <br />determine the existing conditions, which are shown on Figure 2. Figure 3 <br />depicts the regarding plan for this area at the 5H:iV slope with the final <br />location and arrangement of the fill and the reclaimed waterway. Several <br />cross sections and the typical channel for the reclaimed waterway are <br />shown on Figure 4. Included in Addendum 13-lOC is the SEDCAD+ input and <br />output for the waterway from the Hallenbeck stockpond to Culvert YA-1. <br />The discharge utilized for this channel design was based on the results <br />generated for Culvert YA-1. This area will then be topsoiled and <br />revegetated per the approved Reclamation Plan. As an additional <br />stabilizing measure in the reclaimed waterway, XCEL Super Duty SD3 erosion <br />control blankets will be placed in the waterway. These blankets are four <br />foot wide and will be installed along the length of the channel bottom and <br />side slopes in the direction of flow, three blankets wide, with the <br />adjacent blankets slightly overlapped. This option has been discussed <br />with the landowner and the appropriate consent form is provided for <br />insertion into Appendix 22-2. <br />Postmine Channel (Maneotis Property) Reconstruction Design <br />In response to an inspection on July 18, 2007, the Colorado Division of <br />Reclamation, Mining and Safety (CDRMS; formally the Colorado Division of <br />Mining and Geology (CDMGI), requested that Seneca redesign the drainage <br />channel section under the PSCo/WAPA powerliaes disturbed during the <br />dragline move. <br />In accordance with Rule 4.05.4(2)(b), the drainage channel was designed <br />for the 100-year, 24-hour storm event. The 100-year, 24-hour SEDCAD <br />demonstration is presented in Addendum 13-lOB. Figure 5 shows the <br />reconstructed channel section plan view and profile, as well as a typical <br />cross-section. The reconstructed section will be a trapezoidal, grass- <br />lined, channel, approximately 20 feet wide, with 3:1 side slopes, and a <br />0.6 percent bed slope. The calculated depth of flow in the channel is 2.5 <br />feet; the total depth is 2.8 feet. Channel design information is also <br />presented in Addendum 13-lOB. Both channel side slope toes will be <br />protected with North American Green C350 (or equivalent) turf <br />reinforcement mat (TRM), which will provide additional stability and <br />minimize bank erosion. Design and installation specifications for the TRM <br />are presented in Attachment 13-12. <br />The existing low-water crossing, which is used for powerline access and <br />maintenance, has been redesigned. A 15-foot wide and two-foot deep trench <br />will be excavated across the channel at the crossing location. The trench <br />will be backfilled, to the channel invert elevation, with rock riprap with <br />TR-36 13-10-7 Revised 08/07 <br />