Laserfiche WebLink
F)� <br /> scour were computed using methods outlined in Computing Degradation <br /> and Local Scour, by the US Bureau of Reclamation. Hydraulic <br /> parameters used for scour analysis were developed from HEC-RAS ID <br /> modeling. The computed total scour is 10.5 feet with a general scour of <br /> 7.2 feet and a long term scour of 3.3 feet. The design assumes the <br /> thalweg is approximately 10 feet lower than the existing grades at the toe <br /> of the proposed scour berm, yielding a total depth of scour at the toe of <br /> scour berm of approximately 21 feet below existing grade. <br /> A self launching riprap configuration was selected for the scour berm. <br /> This allows for riprap to be placed on the existing surface and to self <br /> launch into scour as it develops along the toe. Riprap launching was <br /> assumed to occur at a 2 horizontal to 1 vertical slope. Riprap was sized <br /> using methodology presented in the US Army Corps of Engineers <br /> (USACE) Hydraulic Design of Flood Control Channels EM 1110-2-1601. <br /> Riprap sizing was completed using the USACE ChanlPro Version 2.0 for <br /> Windows 7 software. The self launching riprap configuration designed <br /> for the 100 year storm event is 9 feet high and 29 feet wide. The design <br /> riprap gradation for the scour berm has a D50 of 28 inches and a <br /> maximum stone size of 42 inches. <br /> 2. The 2008 Kleinfelder Report recommends the use of rock anchors <br /> and shotcrete to reinforce the northeast facing slopes against wedge <br /> failure. The revised HDR Report does not include any discussion <br /> regarding the use of rock anchors or shotcrete. In addition, the <br /> Reclamation Cost estimate does not include any costs associated <br /> with reinforcing the northeast facing slopes. Please clarify if the <br /> recommendations in the 2008 Kleinfelder Report regarding the <br /> stabilization of the northeast facing slopes will be followed. If so, the <br /> design specifications for the placement of the rock anchors and <br /> shotcrete must be provided to the Division for review. If the Operator <br /> will not follow the recommendations in the 2008 Kleinfelder Report, <br /> then additional stability evaluation may be required. <br /> h <br /> Response: M. <br /> The reclamation plan assumes that all northeast facing highwall rock <br /> faces will be buttressed by fill slopes, which is an alternative to <br /> reinforcing, as described in the geotechnical report. Since the fill slopes <br /> will buttress the highwall rock faces, no rock anchors or shotcrete are <br /> required for stabilization and no costs are included. <br /> 2 <br /> hdrinc.com <br /> 1670 Broadway, Suite 3400, Denver,CO 80202-4824 <br /> (303)764-1520 <br />