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�r - -MOU...'JUN, <br /> '-_ Up. <br /> Transit Mix Concrete Co. <br /> Road ditches and clean water ditches are typically trapezoidal ly-shaped to maintain non-erosive <br /> velocities. The ditch side slopes are 3H:1V, and the gradients are typically less than 10%. <br /> Riprap or other armoring is required in areas where ditches are constructed in unconsolidated <br /> materials, for steeper segments, and segments with high flows where the flow velocity exceeds <br /> the erosion threshold of five feet per second. Due to the site conditions, the ditches in the upper <br /> reaches of the site area, within the pit area, and along the access road will be excavated into <br /> bedrock. Thus, no riprap will be required for these ditches. Each ditch will be evaluated on-site <br /> to determine whether bedrock provides sufficient armoring or if riprap will be required. Table G- <br /> 5 presents the values assuming that no bedrock was encountered. <br /> The down drain ditches will be trapezoidal in shape with at least a 4-foot bottom width and 3H:1 V <br /> side slopes. These ditches typically have high grades (up to 20%) and require riprap armoring. <br /> Riprap sizing for channel armoring were determined using a combination of the SEDCAD <br /> program to determine the peak flow, the Hydraulic Toolbox program, Version 4.2 from the <br /> Federal Highway Administration, to determine the anticipated velocity for the channel, and the <br /> USACE EM 1110-2-1601 method for 2% to 20% slopes and the Simons/OSM method in <br /> SEDCAD for slopes steeper than 20%. The ditches have been designed to convey runoff from <br /> the 100-year, 24-hour storm event with no erosion and a minimum freeboard of 0.5 foot. Table <br /> G-5 shows the specifications for each of the ditches. A typical cross-section for ditches is shown <br /> in Figure G-14, and the design reports are included in Attachment G-1. <br /> Ditch CWD-1 is the by-pass ditch to convey unimpacted drainage from the upstream watershed <br /> and convey it through or around the affected area. As sediment detention basin P-DET-1 is <br /> designed to hold the 100-yr runoff event, the flow from the upstream drainage will be limited to <br /> a controlled release for the detention basin. This release is planned to be no more than 25 cfs <br /> and will be conveyed in a lined channel. Transit Mix is planning on using MegaDitch materials <br /> from the SmartDitch vendor for this structure. This prefabricated channel material will allow <br /> streamflow to be diverted past fines stockpile F1 without causing erosion to the stockpile or <br /> increasing sediment loading in the flow waters. Runoff from the south slope flows into the by- <br /> pass channel and the runoff from the affected area to the north is limited by the disturbed area <br /> berm and the grading of the fines pad toward ditch DD-1. As the pile develops and various lifts <br /> advance vertically, the by-pass ditch will also be moved vertically during the dry season. These <br /> movements will allow the undisturbed water to flow around the pile during the life of the <br /> operation. Following completion of the use of the fines pile, the pile will be contemporaneously <br /> reclaimed to minimize the sediment contributions. <br /> Hitch Rack Ranch Quarry Permit Application <br /> October 3, 2017 G-21 <br />