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el" CONTINENTAL MATERIALS CORPORATION <br /> mining industry and will help reduce the sediment volume that erodes from these areas. The <br /> terraces will be built onto the slope as benches. The terrace ditches will be triangularly shaped <br /> with 2.25H:1 V and 10H:1 V side slopes. These ditches have gradients of approximately 2% and <br /> do not require armoring. Terrace ditches have been designed to convey runoff from the 100- <br /> year, 24-hour storm with a minimum of one-foot of freeboard. The typical terrace ditch depth is <br /> two feet. The design for the longest terrace ditch was included in the hydrologic model included <br /> in Attachment G-1. A typical cross-section for terrace ditches is shown in Figure G-2. <br /> The terrace ditches discharge to down drain ditches. Down drain ditches have been included <br /> along the edges of the backfill slope, where a ditch naturally forms. The Cross Channel will <br /> convey water from the middle drainage west of the quarry and has been routed across the <br /> reclaimed slope. The channel will be constructed with a flat channel bottom to prevent losses <br /> in conveyance capacity. The North Channel will convey water from the northern drainages west <br /> of the quarry and from the northern half of the reclaimed slope. The South Channel will convey <br /> water from the southernmost drainage west of the quarry and from the southern half of the <br /> reclaimed slope. The two channels combine to form the Lower Channel, which will convey runoff <br /> from the entire quarry into existing drainages downstream from the quarry. Details on the <br /> channels are included in Figure G-2. The ditches will be trapezoidal in shape with at least a 4- <br /> foot bottom width and 3H:1 V side slopes. The steep channel gradients require riprap armoring. <br /> Riprap sizing for channel armoring was 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-3 shows the specifications for each of the ditches. A typical cross-section for ditches is shown <br /> in Figure G-2, and the design reports are included in Attachment G-1. <br /> Pikeview Quarry Amendment 4 <br /> G-6 <br />