Breckenridge begins repairs to Goose Pasture Tarn Dam
Goose Pasture Tarn, a small, picturesque reservoir in Blue River, was not originally constructed for water storage. The 771 acre-foot reservoir, which serves as the primary water source for the town of Breckenridge, was originally constructed by the Theobald family in 1965 as a recreational asset when the town of Blue River was developed.
While Breckenridge once pulled Sawmill Reservoir as its primary water source, that changed after the Theobalds sold the water rights to the town.
“It was really a win-win-win for everybody, that whole arrangement,” Breckenridge communications manager Kim Dykstra said. “The Theobalds got to keep using it as a recreation source.”
Though the Blue River and the tarn it flows through continue to serve as a reliable source of fresh, mountain water for Breckenridge, the dam that was constructed back in the sixties needs work.
Similar to the Lake Dillon Reservoir’s Dam, there’s a pipe in the bottom that lets water flow through. The problem is, the pipe at the bottom of the tarn lets much less water through; at just 125 cubic feet per second, it would almost be too low for whitewater.
“Runoff is typically above that,” Breckenridge Public Works director Tom Daugherty explained, which is why the town conducted a service spillway to prevent runoff from washing over and damaging the dam. The dam also has a second, emergency spillway for what he calls “thousand year-type events.”
Starting next Monday, the town of Breckenridge will begin lowering Goose Pasture Tarn’s water levels to work on the service spillway, which is in need of repairs.
“We don’t want it to exacerbate any issues with the service spillway,” Daugherty explained. “If you’ve got a flat tire, you don’t want to keep driving on it.”
The tarn’s water level will gradually be lowered by 10 to 20 feet to allow for work on the spillway, retaining the equivalent volume of 50 acre-feet to preserve fish life. Down river, flows will increase by 30 to 40 cfs, an amount that should barely be noticeable.
To start, the emergency spillway will be set up to serve as the “spare tire,” redirecting runoff while water experts seek to shore up and strengthen the service spillway.
“It’s a preventative measure because we’ve been monitoring it for years,” Dykstra said. “It’s like remodeling an old building. You don’t know what’s there until you get in there.”
Snow removal preparation is currently underway, while the more intensive excavation work will start next week — all of which will be regulated by the State Dam Safety engineer.
Daugherty said he expects three to four weeks of work before they allow the tarn to refill; during this time, the tarn will be closed to recreation.
“We’ll just let the normal runoff happen, and it’ll naturally fill back up,” he said.
For the remainder of the summer, the tarn will remain about four feet lower than normal. After finishing analysis of the site, Daugherty said they would have a better picture of whether further repairs would be needed, which could be conducted this fall or later in 2017.
To complicate matters a bit further, the town is not the sole entity with a stake to the tarn; Breckenridge Ski Resort also has rights for up to 400 acre-feet of water for snowmaking. While this spring’s operations will not affect their water rights, if water levels were lowered again in the fall, it could cut closer to the winter season.
“That has such a far-reaching impact on the community,” Dykstra said. “It’s a delicate balance.”
During a normal season, Breckenridge is able to provide water for the 4,500 water accounts in the town with streamflows alone. But during times of severe drought, Breckenridge has an available source of water.
“You don’t know how important water is, until you don’t have it,” Daugherty added.
A SECOND PLANT
The town has also been working on plans for a second water plant, which would allow Breckenridge a backup source of water in the case of a wildfire or landslide contaminating the Blue River. Daugherty said that in the case of a fire, traces of ash are nearly impossible to remove from the water.
As an added benefit, the new treatment plant would allow more area residents to connect to the town’s water system, reducing the number of wells in the area, which would in turn help groundwater tables.
“These people had the foresight to say, we need to make these deals,” Dykstra said. “It’s not just because we’re up in the mountains that we have good water. We really work at it.”
For more information on the dam repairs, please visit http://www.TownofBreckenridge.com/TarnRepairs, or call the Town’s Water Division at (970) 453-3378. For information on the regulations on the Goose Pasture Tarn, please visit http://www.colorado.gov/pacific/townofblueriver/goose-pasture-tarn-rules.
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