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channel slope. A channel roughness coefficient of 0.047 was used to simulate the coarser rip rap in the <br />as -built channel. It was determined that the 100 year peak flow would be contained within the as -built <br />channel. The HEC -RAS cross sections with 100 year water surface elevations are shown in Section A of <br />this appendix. <br />A capacity analysis for the as -built twin 66" CMP culverts was not conducted as part of this technical <br />revision since this was done by Goff Engineering in May 2007. That analysis concluded that the twin 66" <br />culvert would pass the 100 year design event. The analysis is included in Section A. <br />Upper Carbon Junction Channel <br />The Channel Improvement Plan, Exhibit C2.0, shows the extents of the reestablishment of the Upper <br />Carbon Junction Channel. This includes the reclamation /removal of the Carbon Junction Temporary <br />Diversion, realignment of approximately 150 LF of the un -named tributary near the historic confluence <br />with the Upper Carbon Junction Channel and reestablishment of the Upper Carbon Junction channel. <br />The Carbon Junction Temporary Diversion runs along the easterly side of the Upper Carbon Junction <br />Channel approximately 1400 LF from Sta. 26 +70 to approximate Sta. 36 +00. Reclamation of the <br />temporary diversion consists of removing approximately 630 LF of the existing channel and berm from <br />its current confluence with the Upper Carbon Junction Channel (Sta. 26 +70) upstream to the un -named <br />tributary (Sta. 33 +00). The existing diversion berm from the un -named tributary upstream to the end of <br />the berm ( =Sta. 36 +00) will be reclaimed /removed as well. <br />The un -named tributary will be re- routed to its near historic confluence with Upper Carbon Junction <br />Channel at approximate Sta. 31 +60. The new channel is approximately 150 feet long, 3' bottom width <br />and 3' deep. It will be armored with 12" nominal diameter rip rap to prevent erosion. A HydroCAD <br />analysis was completed to determine the 10 year design flow generated from the un -named tributary <br />basin (Basin 2) and the capacity of the channel re -route (Section C). The 10 year design flow of 25.51 cfs <br />will be contained within the proposed channel cross section. Discharge velocities at the discharge of the <br />re- routed un -named tributary to the Upper Carbon Junction channel are 4.6 fps and should not require <br />additional rip rap at the confluence. <br />At the current confluence of the existing Carbon Junction Temporary Diversion and the Upper Carbon <br />Junction Channel an area of sediment deposition has formed creating a sump condition on the upstream <br />side of the confluence. This portion of the Upper Carbon Junction Channel, approximately 100 LF, will <br />be regraded to remove the sediment deposition and sump condition, and provide positive drainage <br />along the channel. The regrading work should match the existing channel at the upstream and <br />downstream ends, reestablishing the channel to its' near historic condition. <br />The intent of the re- grading of the temporary diversion is to provide a mostly uniform slope along the <br />easterly bank of the Upper Carbon Junction Channel, returning it to its near historic cross section. <br />Grading operations should be done in a manner to minimize import/export of material and to minimize <br />disturbance of existing vegetation as much as possible. All areas disturbed during construction activities <br />shall be covered to a depth of 6" with native topsoil material and re- seeded with a native grass mixture. <br />All work shall be in accordance with the Colorado Division of Reclamation, Mining and Safety, <br />Regulations of the Colorado Mined Land Reclamation Board. <br />