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I I I I I I I I I I I I I I I I I I I in the watershed between the additional storage sites and the Larimer- Weld Canal is in the vicinity of 500 cfs. Reservoir storage sites at strategic locations in the Upper Watershed between Douglas Reservoir and the Larimer-Weld Canal were identified. Six such sites were evaluated in that area. Each of the sites was considered to be feasible on the basis of topography and location. It was determined that storage sufficient to reduce downstream flows to 500 cfs could be generated by various combinations of the six storage reservoir sites. Possible approaches to disposition of the residual 500 cfs flow at the Larimer-Weld Canal were evaluated. Ditch company personnel suggested that the Larimer-Weld Ditch could transmit the flow spill point downstream on the Ditch. They also suggested that the Ditch Company might be willing to allow this if the City and County were willing to assist the Ditch Company in routing irrigation flows down Dry Creek from Douglas Reservoir to the Larimer-Weld Canal. A spill point was identified at the east end ofLindenmeier Subdivision. Stormwater from the spill point could be carried downstream in a channel along the alignment ofthe existing Lindenmieier Lake Outlet Canal. This canal joins the natural channel of Dry Creek at a point immediately north of Vine Street. Recommended Alternative The combination of flood storage and downstream diversion of the residual flow was identified as the most feasible alternative that would be effective for the intended purpose. In summary, the plan would consist of enhancement of the spillway on an existing on stream irrigation storage reservoir, enhancement of Dry Creek to carry irrigation water, construction of two detention storage reservoirs, and construction of a spillway and outfall channel downstream of the Larimer -Weld Canal. A need exists for an outfall channel to carry "Local Basin" runoff as well as "spilled" Upper Basin stormwater from the intersection of Vine Street and Dry Creek downstream to the Cache La Poudre River (See Concept Basin Map, next Page). As part of the recommended plan, a channel would be constructed across Vine downstream along the north side of the Downtown Airpark runway to join with the existing Timberline Channel, which provides an outlet for stormwater across State Highway 14. It was recognized that the Larimer- Weld Canal might be full at the time rainfall occurs over the Dry Creek Basin. For that reason, the recommended improvements include an automatic data transmittal and control (SCATA) System. This system will consist of sensing devices which provide warning that flood water will be coming down Dry Creek. The system then automatically closes the head gates on the ditch at the diversion structure on the Cache La Poudre River, and at the same time opens the spill gates at the spill point. The City of Fort Collins currently has in place a system of early warning stream flow and precipitation monitoring sites. Extension of that system to provide automatic gate controls is well within the limits of current technology. The cost ofthe improvements, including ancillary structures, design and construction engineering, construction right of way and contingency was estimated by URS to be nearly $5,000,000. The cost of right of way for flood easements for detention structures was estimated 7