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I' I I I I I I I I I I I I I I I I I I . West Fork Kenneys Run from 23rd Street through the Golden High School property Sanitary design. sewer confl i cts will be resolved on an i ndi vi dua I Utility field surveys will be required prior to final basis in final design. 5. Grade Stabilization Structures - Concrete grade beams are planned for the upper reach of Tucker Gul ch and the lower reach of Cressmans Gulch to limit erosion and degradation of the existing natural channels. The grade stabilization structures are also commonly referred to as check dams and can be made from concrete 3- to 5-feet deep. The concrete structures should extend completely across the channel and into the sloped banks. Riprap protection is also recommended in the vicinity of the check dams in considering the steep natural stream slopes and the potential for side bank erosion. Stormwater Detention Basins 6. Storm Sewer Inlets - Storm sewer inlets are recommended to improve normal street drainage for all storm sewered reaches of Kenneys Run. "Type R" inlets should be used, as designated by the Colorado Depart- ment of Highways, and should be designed using Standard Curb-Opening Inlet Charts. All inlets shown on the master plan drawing are standard 15' inlets. Inlet openings will vary in final design. Three stormwater detent i on basi ns are pI anned for the Kenneys Run bas into control stormwater runoff for the more frequent runoff events (2-, 5-, and 10-year storms). The facilities also provide limited peak flow reductions for the less frequent events, such as the IOO-year design storm. All facilities were designed to accommodate flows in excess of the IOO-year runoff and have maximum IOO-year oondi ng depths of I ess than 10 feet. The 2-year developed flow rate was used to size the principle outlet works. Emergency spillways and road grade overflow sections require grass-covered riprap to be aestheti- cally pleasing, to simplify maintenance, and to protect against erosion. Maximum embankment side slopes of 4:1 should be used. The impoundment areas should have minimum cross slopes of 2% to facilitate drainage. 7. Irrigation Ditch Flow Restrictors - Flow restrictors are planned for the Welch Ditch downstream of the Welch Ditch Detention Basin and the Boys School Road Detention Basin. The restrictors should be concrete structures sized to pass maximum irrigation flows as defined by the capacity of the existing irrigation ditch. The restrictors, combined with recommended grading of the downstream ditch bank, will force the release of excess stormwater flows at controlled locations. All three detention basins are classified as regional facilities and are not intended to fully compensate for benefits provided by smaller, on-site facilities. The ponds were designed for the storage volume available, without excavating additional storage. Additional peak flow attenuation may be achieved by excavating the storage areas and providing modified outlet works for controlled more-frequent runoff events. If desired, such alternatives can be investigated in final design. Ri ght-of-Way 8. Trashracks - Trashracks are proposed for cuI vert and storm sewer inlets to control build-up of debris and prevent potential blockage. Trashracks should be designed with safety in mind and inclined with a minimum slope of 4:1. Where planned improvements fall within private property limits, land acquisi- tion is required. Key right-of-way acquisitions for the Tucker Gulch/Kenneys Run master plan include: Utility Conflicts . A 70-foot ri ght-of-way for the Tucker Gul ch channel improvements below State Highway #58. Existing utilities, other than sanitary sewers, will be relocated as needed. VI-3