Oak Creek is preparing to move forward with important upgrades to a 68-year-old dam at Sheriff Reservoir.

Town Administrator David Torgler said officials made initial repairs at the dam after observing a sinkhole in September 2018.

“The repair worked perfectly, but in 2021 the Colorado Division of Water Resources issued a reservoir restriction and that is because there was a belief that the spillway was inadequate,” Torgler said.

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With the threat of a dam breach, the town worked with the engineering firm W. W. Wheeler & Associates to create a hydrology study to determine what repairs would be necessary. Completed this year, the report used updated high elevation hydrology formulas to anticipate how much water the dam and its spillway would need to handle in a maximum flood event.

According to Torgler, the study found the spillway would need to be expanded from its current 32 feet to 55 feet across. Approved by the state’s engineer Monday, the study is key, the town administrator said, because it was originally believed the expansion improvement would need to be 330 feet across.

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After completing work to replace the headgate on the dam, which sits close to the structures base on the reservoir side, the project will now turn to the completion of the design engineering for the spillway enhancements, Torgler said.

To date, the town has spent $520,000 for design engineering for the headgate and the purchase and installation of operating equipment and $320,000 for final design work. Cost estimates for the spillway work will be ready by the end of the year.

Torgler said that without performing the dam improvements, there would be a significant reduction in the amount of water stored in the reservoir. He noted the reservoir provides recreational opportunities for locals and visitors, but it is also Oak Creek’s drinking water supply.

“Usually in August there is a two- to three-week period of time where we rely on that water because Oak Creek dries up enough that we have to rely on that as a resource,” Torgler said. “But then there are also agricultural users that will now be able to rely upon the reservoir as a resource to provide steadier source of water through a longer period of time in the summer months in the fall.”

To date, funding for the engineering and construction has been provided by the state, Routt County, the Colorado Water Conservation Board, the Upper Yampa Water Conservation District, the Colorado River District, the Yampa-White-Green Basin Roundtable, and the town’s Federal American Rescue Plan Act of 2021 funds.

“We very much appreciate the state and county and water districts for their support of this project — we can’t thank them enough,” Torgler said. “The town of Oak Creek is as small community, and it doesn’t have the financial resources to rehabilitate the facilities we have, so their help is greatly appreciated.”