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• The south collection ditch is divided into four (4) channel sections, each <br />having different channel slopes and configurations as shown on Figure 3, <br />Refuse Disposal Area Drainage Plan. <br />Sections A and B are designed as trapezoidal channels with 5-foot bottom <br />widths and 2H:1V sideslopes. Section A extends for approximately 920 feet <br />at a 1.4 percent slope, and Section B extends for approximately 470 feet <br />at a 2.2. percent slope. The flow velocities for Section A and Section <br />B are 3.4 fps and 4.1 fps, respectively. Vegetative channel protection <br />is provided for these sections. <br />Section C is designed as a trapezoidal channel with an 8.5-foot bottom <br />width and 2H:1V sideslopes. The channel section extends approximately 950 <br />feet at a 4.4. percent slope. The design velocity is 5.0 fps, therefore, <br />the vegetative lining provides adequate erosion protection. <br />• Section D is designed as a trapezoidal channel with a 5-foot bottom width <br />and 2H:1V sideslopes. The channel extends approximately 300 feet at a 5.0 <br />percent slope. The calculated velocity (6.5 fps) exceeds 5.0 fps, <br />therefore, rock riprap (D,~ = 9.5 inches) is installed in Section D to <br />prevent erosion. The riprap is placed to an approximate depth of 20 <br />inches along the channel bottom and sideslopes. Appropriate bedding <br />material was placed and spread prior to riprap placement. <br />Design details and channel characteristics for each channel section are <br />summarized by Figure 5, Refuse Collection Ditches - Design Detail. Refer <br />to Table 17, Refuse Collection Ditches, 100-Year, 24-Hour Hydrography <br />Analysis, at the end of this section, for computer printouts. <br />• <br />118 <br />