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I I I I I I I I I I I I I I I I I I I GENERAL FIRM EXPERIENCE West Toll Gate Creek Channel Rehabilitation Denver Urban Drainage and Flood Control District Montgomery Watson was retained by the Urban Drainage and Flood Control District (UDFCD) to provide a technical analysis, final design and construction services for the stabilization and rehabilitation of West Toll Gate Creek between Alameda Parkway and Chambers Road in Aurora, Colorado. Phase I of the work was completed in 1988 and consisted of improvements to the lower reach. Phase II is currently underway and will address the upper reach. This reach of the stream is located in Delaney Farm Park, an area that the City of Aurora desired to main- tain in its historical natural condition as much as possible. The stream channel had been de- grading and moving laterally, resulting in bank erosion and formation of steep, unstable banks. Further degradation would impact utility crossings and a bridge foundation and the steep banks were a safety hazard to park users. The technical study evaluated the impacts of past upstream and downstream channel improve- ments on the streambed degradation and made recommendations on how best to stabilize the channel in the project area. Hydraulic analyses included determination of the equilibrium bedslope, the velocity distribution, water surface levels for various events, and bankfull capac- ity. A series of drop structures and bank stabilization measures were proposed to provide the necessary grade control. Drop structures constructed of either concrete or sheet piling were evaluated. The concrete vertical drop structure was selected. To minimize the visual impact, the majority of the drop structure is buried. Exposed surfaces are treated architecturally to be more visually pleasing. Riprap bank protection is buried and revegetated using stock taken from local material. A minor amount of channelization and bank shaping was completed during Phase I to remove near-vertical banks in areas frequented by public users of the Park. A total of 8 drop structures will be installed in the I-mile long reach. Total construction cost is approximately $700,000. Extensive coordination among the UDFCD, the City, the Denver Water Department, the local historical society, and the adjacent homeowner's association has been required. Two formal public meetings were held. The Phase I work has been in operation for nearly 10 years and has functioned as intended. 7 MONTGOMERY w.<Q'SON ((D)