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I I I I I I I I I I I I I I I I I I I 1966) irrigation right at the 29 Road Pump Station. All return flows within the District boundaries belong to the District. Water right lands within the District have a base allocation of 8.18 gallons per minute (gpm) per acre, continuous flow. The system is classified as an "on demand" system, which means that the canals must be at the proper levels at all times to deliver at any and all headgates the required 8.18 gpm. This may be reduced in times of shortage by "pinching" headgates on the system to restrict the flows at the headgates. Project Description and Alternatives The purpose of this project is to provide a dependable means for the District to continue providing irrigation water to landowners while ensuring no damage to nearby homes and highway. A Technical Feasibility Study was completed in 2005, funded by a matching grant from the Colorado Water Conservation Board. In that study, four alternatives were considered: 1. Repair the siphon. 2. Replace the siphon - cast in place 3. Replace the siphon - precast option 4. No action. Alternative #1 The existing Stokes Gulch inverted siphon is in poor condition. Originally constructed in the 1920's, concrete is spalling off of the structure, leaving large areas of exposed reinforcing and willows are growing on top of the siphon, the roots of which have punched through the existing concrete. The siphon has a running water leak on the downhill side, facing Highway 6, plus leaks in many other places on the siphon. A failure during irrigation season could lead to a lengthy period without water for irrigation needs. Repairing the siphon is not practical or feasible. Alternative #2 The structure would be poured-in-place. The conduit would be a 12' x 12' square box. Existing inlet and outlet concrete would be salvaged and rehabilitated to the maximum extent possible. The cost of this option would be about $570,000. Since the Technical Feasibility Study was completed, a large fault has been discovered in the concrete lining the Power Canal from the invert of the Stokes Gulch Siphon stretching upstream approximately 300'. Emergency repairs were made in order to keep water in the canal during the winter of 2005/2006, however, a permanent repair will now be added to the replacement project in order to stop the leaking that is affecting the home immediately below this area. The cost ofthat repair is estimated at $85,700 and would be added to the $570,000, making a total project cost of $656,000. Since the cost ofthis option would be higher than the cost of the pre-cast option, this is not the preferred alternative. Orchard Mesa Irrigation District Feasibility Study Stokes Gulch Siphon Page 7