Rio Grande - Manassa Conejos River & N Branch Stablization_Application

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Water Supply Reserve Account - Grant Application Form Form Revised May 2007 This technology has proven successful on several reaches of the Conejos River over the past feiv rears. The operators and staff of Robins Constriction are becoming -,vell known for the quality and effectiveness of their work in this area and their expertise with this kind of project. There are no TABOR issues involved that might affect MLI or this project. SCOPE OF WORK Please summarize the proposed scope of work. Please refer to Part 2 of the Criteria and Guidance document for detailed requirements. On the following page there is an example format for the Scope of Work. You can use the example format or your own format, provided that comparable information is included. The scope of Nvork should outline by task how the water activity- will be accomplished. It is important that the scope of work detail the specific steps, activities/procedures that will be followed to accomplish the Avater activity and the specific products/deliverables that will be accomplished. The scope of work should include but not be limited to: task description, key personnel, budget, schedule and deliverables and the final report/project documentation upon completion of the water activity. Summary: The existing darn, or Core, is a cast-in-place concrete structure with a concrete apron on the main river channel and a concrete headworks with five gate openings on the north diversion channel or the North Branch. The Core is about 70 feet wide. The headworks structure is about 55 feet long and six feet high, to the top of the piers. The gates were designed to be opened to a height between 4 and 5 feet and vary in width from 6.5 to 8.9 feet. See figure 1 for a plan view and figure 3 for a section through the headivorks. There are no as-builts to be found. An aerial photograph is nieluded. Obiectives: Current NRCS design criteria confirm the deliverables identified in the September 1994 US Bureau of Reclamation study: 1. Pass up to 500 cubic feet per second into the north channel with control accomplished by Diversion Gates positioned at the entrance to the north channel. It should be noted that flows referenced in that study represented flows in the Cone jos River as measured at the Mogote stream gauge approximately 7 river miles upstream. Actual flows at the structure are less than those measured at the Mogote gauge due to several upstream diversions. 2. Determine water surface elevations necessary to accomplish the desired 500 cfs delivery into the north channel in relation to mean sea level or relative to the channel bottom. Provide for majority of gravel transport down the main channel. The river deposits a moderate volume of gravel bed load front of the structure during high flows. This accumulated gravel causes a decrease in flows the north diversion channel and increases maintenance. 4. Realign the main channel numediately upstream of the Diversion Gates by excavating the existing gravel bank on the north side of the river (figure 1). The realigned bank should fit within the District's right-of-way north of the river adjacent to the dam and headworks. To reduce erosion, riprap should be placed on the left bank upstream of the headivorks and on the right bank 21