August 19, 2015

Progress made on Grizzly Reservoir repairs

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The sediment at the bottom of Grizzly Reservoir has been revealed after the water in the 570 acre-foot reservoir was drained this week after a problem arose with the dam's outlet works. As the reservoir was drained, about 20 acre-feet of muddy water flowed out of the bottom of the reservoir into Lincoln Creek and the Roaring Fork River.

Courtesy photo:/Twin Lakes Reservoir and Canal Co.

The sediment at the bottom of Grizzly Reservoir has been revealed after the water in the 570 acre-foot reservoir was drained this week after a problem arose with the dam's outlet works. As the reservoir was drained, about 20 acre-feet of muddy water flowed out of the bottom of the reservoir into Lincoln Creek and the Roaring Fork River.

A view of the recently drained Grizzly Reservoir. Operators are now cutting a drainage channel to divert the flows of Grizzly and Lincoln creeks directly into a diversion tunnel so they can inspect the damaged outlet works on the dam.

Courtesy photo: / Twin Lakes Reservoir and Canal Co.

A view of the recently drained Grizzly Reservoir. Operators are now cutting a drainage channel to divert the flows of Grizzly and Lincoln creeks directly into a diversion tunnel so they can inspect the damaged outlet works on the dam.

The prospect of another round of muddy water coming out of Grizzly Reservoir and into the upper Roaring Fork River due to a heavy rain event has been reduced, although not eliminated.

A channel dug through the sediment at the bottom of the drained reservoir was completed Monday night and the flow of Lincoln and Grizzly creeks, about 32 cubic feet per second, is now being diverted directly into the diversion tunnel that runs under the Continental Divide.

“We’re making progress and heading in the right direction,” said Scott Campbell, general manager of the Twin Lakes Reservoir and Canal Co., which owns and manages Grizzly Reservoir and the Lincoln Gulch Diversion Dam.

About 10 days ago, operators at the dam and reservoir discovered a tree in the dam’s outlet works.

Once the tree was removed and the gate in the outlet works was successfully closed, water was still coming through the outlet, apparently due to a broken seal around the gate.

Campbell made the call to drain the reservoir, which can hold 570 acre feet of water.

Most of the water in the reservoir was sent through the diversion tunnel, but on Aug. 10 about 10 to 20 acre feet of brown muddy water at the bottom of the reservoir ran down Lincoln Creek and into the Roaring Fork River, turning the river brown as it flowed through Aspen and Basalt.

Since then, a Twin Lakes employee has bulldozed a channel through the sediment in order to redirect the flow from Lincoln and Grizzly creeks away from the outlet works in the dam, in order to get a good look at the situation.

On Thursday, once Highway 82 over Independence Pass reopens after the USA Pro Challenge bike race, Campbell plans to inspect the dam with a consulting engineer and a state dam safety engineer to determine the scope of the problem.

It’s possible that rain could still wash muddy water out of the empty reservoir, but if the rain stays away, the water in the Roaring Fork should now be clearing up, Campbell said.

Editor’s note:
Aspen Journalism is collaborating with The Aspen Times and the Glenwood Springs Post Independent on coverage of rivers and water. The Times published this story on Wednesday, Aug. 19, 2015.

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