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than adequate even when half full with sediment. Reach 8 is a large open channel which drains both reach 6 and 9. 5.3 Drainage Structure Summary A brief description of each structure is given: Reach 1 - open channel with a minimum trapezoidal design section two feet deep and two feet wide. Reach 2 - 18" corrugated plastic pipe receives from reach I and carries it to the open channel behind the office. Reach 3 - 18" CMP which begins at the West Drainage diversion and connects with reach 4. Reach 4 - 18" corrugated plastic pipe which is connected to reach 3 and discharges into the open channel behind the office, reach S. Reach 5 - open channel which conveys diverted East and West Basin runoff to the offsite discharge point. Reach 6 - trapezoidal open channel with a depth and width which both vary from one to two feet. Reach 7 - 36" concrete pipe which drains portions of the yard. Reach 8 - trapezoidal open channel with five foot bottom width and 5 foot depth. Reach 9 - 24" CMP. Reach 10 - trapezoidal open channel with a depth of two feet and bottom width of one ft. Reach 11 - 30" CMP. Reach 12 - open channel swale, average shape is triangular with a depth of 0.5 feet and a ~ topwidth of 10 feet. Reach 13 - triangular open channel with a depth of one foot and a top width of 1.5 feet. The required discharges from the hydrologic analysis reported on in the Section 4.1 and the computed discharge capacities are summarized in the following table. Note that in all cases the required discharge is exceeded by the actual capacity. DESIGN CHARACTERISTICS FOR PIPES AND CHANNELS Location Existing/New Required Discharge Slope Diameter or Depth x Width (ft) DischargeC apacity reach 1 existing channel 5.9 cfs 0.060 trap, 2x2 22-86 cfs reach 2 new pipe (1993) 5.9 cfs 0.060 18" 11.2 cfs reach 3 existing pipe 4.6 cfs 0.100 18" 14.4 cfs reach 4 new pipe(1993) 4.6 cfs 0.038 18" 8.9 cfs reach 5 existing channel 10.5 cfs 0.041 trap, 1.7x4 17.2 cfs 7 June 1995