Colorado - Old Dillon Reservoir Enlargement_Water Activity Summary

Home Browse Search

Summit County, the Town of Dillon and the Town of Silverthorne are cooperating on an enlargement of Old Dillon Reservoir to serve existing and future needs. The proposed enlargement will total between 180 ac-ft and 255 ac-ft depending on final cost estimates for different alternates that will be produced during the final design phase of the project in the fall of 2008. The Town of Dillon has a 1939 storage right for 46.14 ac-ft in the Reservoir decreed in 1806 and an additional 20 acre-feet of water in exchange for releases from Clinton Gulch Reservoir(95CW077). The Town of Dillon and Summit County have conditional storage rights for the enlargement. Dillon and Silverthorne have limited existing raw water storage, which makes the development of this reservoir enlargement project extremely important to protect the Towns from the possibility of drought and potential pollution in Straight Creek and Blue River watersheds. This reservoir will also provide important security and flexibility in the use of the parties' rights in Clinton Gulch Reservoir and Dillon Reservoir. The Town of Dillon plans to store a combined total of 96 acre-feet of water in the enlarged reservoir for use as an alternate supply in the event that the Town's Straight Creek water supply would become contaminated due to forest fire or pollution from an incident along the 1-70 corridor. Town staff estimates that the Town will need approximately 2.5 ac-ft of raw water per day to meet the peak summer demand at build out. The Town of Silverthorne plans to store approximately 20 acre-feet in the enlarged Reservoir. The Town will use this water primarily by including the water in its augmentation plan for out-of-priority depletions caused by municipal wells. Summit County plans to store its share of the 150 acre-foot first enlargement right for the benefit of Summit County interests, including water users participating in its augmentation plan. Enlarging old Dillon Reservoir will require a USFS Special Use Permit, a U.S. Army Corps of Engineers 404 permit (wetlands issues), a review by the Summit County Planning Department (and possible permitting) and various intergovernmental agreements describing the relationships between Dillon, Summit County and Silverthorne. Summit County, Dillon and Silverthorne have engaged (through IGA with Summit County) the assistance of the Colorado River District to help advance the project. Currently the Colorado River District provides project management and cash flow buffering. The following studies have been prepared for or are relevant to this project: ?December 2004, Boyle Engineering Corporation issued the UPCO/Summit County Water Supply Study to identify water quantity and quality issues in Grand and Summit Counties ?March 2002, Science Applications International Corporation (SAIC) prepared a Final Biological Assessment/BiologicaI Evaluation for Old Dillon Reservoir and Dillon Ditch for a USFS Special Use Permit for the Dillon Ditch and Old Dillon Reservoir. ?December 2001, Science Applications International Corporation (SAIC) prepared a "Final Wetland Technical Report," providing documentation of all wetlands and anticipated wetland impacts for a USFS Special Use Permit for the Dillon Ditch and Old Dillon Reservoir. - 2 -