Forest Service eyes Old Dillon Reservoir expansion |

Forest Service eyes Old Dillon Reservoir expansion

Bob Berwyn
summit daily news
Summit County, CO Colorado

Illustration/Jason Smith

SUMMIT COUNTY ” The U.S. Forest Service is requesting public opinions about a plan to expand Old Dillon Reservoir.

As envisioned by Summit County, the enlarged reservoir, located off the Dillon Dam Road, would be contained by two earth dams about 28- to 38-feet high. The expansion would impact about 20 acres of land, including 14.5 acres on the White River National Forest ” thus the Forest Service analysis.

Right now, the reservoir holds about 46 acre feet of water. The enlargement would expand that capacity to about 255 acre feet. An acre foot is about 326,000 gallons of water, enough to supply a family of four people for a year.

Construction would require 120,000 cubic yards of excavation, 80,000 cubic yards of embankment fill 10,000 cubic yards of imported rock fill and 1,000 feet of pipe for an outlet to the Blue River.

Local towns and the county say enlargement is a key strategy to maintain local water supplies. Water in Old Dillon Reservoir could be especially valuable for Dillon. The town relies mainly on surface water from Straight Creek, potentially vulnerable to drought and contamination.

Pending completion of the Forest Service analysis, work could start on the ground in 2009, said County Commissioner Tom Long.

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“It’s a strategic spot … it would be valuable water,” Long said. The project could be developed at a cost of about $40,000 per acre foot. For the sake of comparison, Long said water from Clinton Gulch reservoir costs about $35,000 per acre foot.

The project is a partnership between Dillon, Silverthorne and Summit County. Long said all those entities could benefit from an increase in capacity.

Along with planned tree removal in the area, construction of the new reservoir will definitely have some visual impacts, said U.S. Forest Service Ranger Paul Semmer.

The logging is part of a pine beetle-related forest health project, and the new dams will be all the more visible because of the tree removal, said Mike Claffey, the environmental consultant for the project.

Mitigation for visual impacts could include giving the dams an undulating face and replanting them with native grasses, Claffey said.

Claffey said the enlargement would impact some wetlands along the shore of the existing reservoir (0.43 acres), as well as some wetlands along a ditch associated with the water supply for the reservoir. The plan is to mitigate wetland impacts nearby on National Forest land, Claffey said.

U.S. Forest Service community planner Paul Semmer will give presentation on the enlargement during the Feb. 21 Snake River Planning Commission meeting, 5 p.m. at Dillon Town Hall.

The scoping notice for the project, along with a sketch map, are avaiable from the Dillon Ranger District. Call (970) 468-5400 to request the scoping notice or call (970) 262-3448 for more details on the proposal.

Comments during this phase of the review are due by Feb. 22. Send comments to Paul Semmer, community planner, U.S. Forest Service, Dillon Ranger District, White River National Forest. P.O. Box 620, Silverthorne CO 80498. Fax comments to (970) 468-7735 or email them to

When submitting comments, include your name, address, phone number, organization represented if any; the title of the project you are commenting on (Old Dillon Reservoir enlargment); specific facts, concerns or issues.