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I I I I I I I I I I I I I I I I I I I 24 1. Pipe Systems. Pipes were proposed to convey the lO- year flood, as a minimum, along the routes of the main channels. Inlets are recommended at the illustrated locations. However, the proposed pipes represent essentially a "trunk" system, to which local laterals should be added. Numerous other inlets attached to future laterals will be required to fill the proposed pipes to their capacities. Access to all pipe systems for maintenance is provided by either public rights- of-way o~ acquisition of drainage easements. 3. Irrigation Ditches. The Rocky Mountain Ditch crosses both Dry Gulch and North Dry Gulch, and the Agricul- tural Ditch crosses Dry Gulch. At all three locations, overflow structures are proposed which would cause storm flows (those in excess of normal ditch flows) to be discharged out of the ditches and into the planned facilities. This insures that storm runoff flows will not be conveyed along the ditches and released at uncontrolled points. 2. Open Channels. All open channels consist of cross sections as illustrated on the plans. All contain concrete, low flow channels. Channel sideslopes are generally on 4:l slopes with natural grass cover or 2:l slopes protected by tiered gab ions , concrete lining, or similar covering. The longitudinal channel slopes are controlled, through regularly spaced drop struc- tures, to convey the lO-year flow at average velocities of 7.5 feet per second or less. While the 100-year flow is generally contained within the channels, the flow velocities may exceed 7.5 feet per second, and thus may cause minor erosion damage. Maintenance access is planned along all open channels from either public streets or by roadways which will also serve as hiker- biker facilities. 4. Street Crossings. Colfax Avenue, Kipling Street, and Wadsworth and Sheridan Boulevards are considered arterial streets within the Dry Gulch basin. The proposed facilities at these street crossings are sized to convey the lOO-year flood in such a manner that the water depth at the centerline will not exceed six inches. This is considered to be sufficient assurance that the streets will remain open for use by emergency vehicles during a major flood event. Facilities at all other streets are sized to either convey the lO-year flood without overtopping the roadway, or the lOO-year flood without allowing flooding to exceed eighteen inches at the street gutter flowline, whichever criterion re- quires the larger facility. At all street crossings, existing utilities must be either adequately protected or relocated.