PERMFILE57171 - Laserfiche WebLink

Home Browse Search

~ .. The ditch collects surface runoff from the drainage area north of the access road and runoff contributed by CD-1. The runoff is routed directly to Sedimentation Pond No. 5. The access road collection ditch is divided into three (3) sections (Sections A, B and C). Section A borders the north edge of the access road and extends from the refuse pile to the county road. Section B borders the north edge of the county road and extends from the access road to Culvert 38. Section C borders the north edge of the county road from Culvert 38 to Pond 5. Section A of the access road collection ditch is designed to safely pass the peak flow from the 10-year, 24-hour event. It is a trapezoidal channel with a 4.0 foot bottom width and 2H:1V sideslopes. The peak flow calculated for the 10-year, 24-hour event is equal to 3.89 cubic feet per second. The channel slope is 9.6 percent with a design flow velocity equal to 4.4 feet per second. The ditch has a natural cobble surface to prevent erosion. Refer to Figure 2, Sediment Collection Ditches - Design ~• Detail, for design details and channel characteristics. Section B is designed to safely pass the peak flow from the 10-year, 24- hour event. It is a trapezoidal channel with a 4-foot bottom width and 2H:1V sideslopes. The peak flow calculated for the 10-year, 24-hour event is 13.8 cubic feet per second assuming all watersheds draining to Sedimentation Pond No. 5 peak simultaneously. The channel slope is 5.0 percent with a design flow velocity equal to 4.5 feet per second. Section C is designed to safely pass the flow from a 10-year, 24-hour event. It is a trapezoidal channel with a 5-foot bottom width. The peak flow for the 10-year, 24-hour event is 27.3 cfs. The channel slope is 6.3 percent with a design flow velocity equal to 6.8 feet per second. Design Calculations - Sediment Collection Ditches . Collection Ditch No. I (CD-1) ,.~ ~ 1 ,\ 96 R Revised - December, 1991