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• West Refuse Collection Ditch • North Refuse Collection Ditch • • South Refuse Collection Ditch All ditches are designed to safely pass the 100-year. 24-hour storm event providing 0.3 feet of freeboard. Peak flows calculated by SEDCAD+ for each channel are shown on Figure 5. Refuse Collection Ditches - Design Detail. West Refuse Collection Ditch. The west refuse collection ditch extends along the western boundary of the refuse disposal area between the toe of the refuse pile and Permanent Diversion No. 1 as shown on Figure 6, Refuse Disposal Area - West Boundary section A-A'. The west collection ditch collects all surface drainage flowing off the west edge of the pile and routes it to the northwest corner of the pile where it flows into the north refuse collection ditch. Initially, the west refuse ditch will be placed at the toe of refuse pile. Upon completion and regrading of the minor Swale resulting form soil recovery operations, the ditch will be reestablished in the base of the Swale. • Both the initial and final west refuse collection ditches are divided into three (3) sections as shown on Figure 3, Refuse Disposal Area Drainage Plan. Each section has a different channel slope. The entire length of the ditches are designed as trapezoidal shaped, vegetated channels with 2H:1V sideslopes. The design flows in all sections are less than 5 feet per second. Therefore, no erosion protection is required. However, rock riprap (DSO = 8 inches) is placed in Section C where it joins with the north collection ditch to prevent erosion at the channel bend. The riprap is placed to an approximate depth of 18 inches along the channel bottom and sideslopes. Appropriate bedding material was placed and spread prior to riprap placement. Design details for each channel section are summarized by Figure 5. Refuse Collection Ditches. 100-Year, 24-Hour Hydrograph Analysis, at the end of this section, for computer printouts. C~ 114 Revised 12/14/94