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Page Exh.7-25E-1 Revision Date: 6/16/21 <br /> Revision No.: TR-149 <br />Exhibit 7, Item 25E <br />Collom Haul Road Channel Configurations <br /> <br />Several channels will be utilized to manage storm water runoff from undisturbed and disturbed <br />areas on and along the Collom Haul Road. These channels will route water from culvert outlets <br />and road cutouts to small sumps (best management practice structures for storm water), to allow <br />sediment to settle out and to decrease peak flows prior to discharge. This section addresses the <br />configuration of these channels along the Collom Haul Road. <br /> <br />Exhibit 7, Item 14 in Volume 2D describes the hydrologic methodology used for channel <br />assumptions. Runoff curve numbers assigned to the undisturbed and disturbed lands have been <br />selected in accordance with Table 1 in the Introductory Text for Exhibit 7 in Volume 2D. For <br />channels protected by a riprap liner, selection of minimum riprap size is done using the <br />Simons/OSM method in SEDCADTM. <br /> <br />The following pages present the results of the SEDCADTM models for channels C-1 through C-9. <br />A SEDCADTM model for channel C-2 is not included as C-2 is a native channel that is stable and <br />will not have a formal channel constructed in it. It will have some small rock check dams <br />installed to slow down flows down gradient of the Collom Haul Road in that corresponding <br />drainage. <br /> <br />Location, contributing watersheds, and on the ground hydrologic conditions for these channels <br />are reflected on Figures Exh. 7-25E-1 through Exh. 7-25E-5. The dimensions, lining type, and <br />flow characteristics all the channel configurations are included in the SEDCADTM attached <br />outputs for each specific channel. A summary of the channel configurations and minimum <br />construction specifications are summarized on the table below. <br /> <br /> <br />Channel Lining <br />Type <br />Specified <br />Depth <br />Bottom <br />Width <br />Side <br />Slope, <br />1H:1V <br />Minimum <br />Rip Rap, <br />D50 (in) <br />C-1 Riprap 3.0 10.0 2:1 6.0 <br />C-2* - - - - - <br />C-3 Riprap 3.0 5.0 2:1 9.0 <br />C-4 Riprap 3.0 5.0 2:1 3.0 <br />C-5 Riprap 3.0 5.0 2:1 6.0 <br />C-6 Riprap 3.0 5.0 2:1 3.0 <br />C-7 Erodible 3.0 2.0 2:1 NA <br />C-8 Erodible 3.0 Triangular 2:1 NA <br />C-9 Erodible 3.0 Triangular 2:1 NA <br />*C-2 Channel is the pre-mine natural grass channel and will have several small rock check dams <br />installed only due to the minimal watershed reporting.