#ColoradoRiver: Risk of failure at Wolford dam ‘very remote’ — The Grand Junction Daily Sentinel #COriver

Wolford Mountain Reservoir
Wolford Mountain Reservoir

From The Grand Junction Daily Sentinel (Dennis Webb):

A review has led to the determination that there’s no need for the Colorado River District to make potentially expensive repairs to its Wolford Mountain Reservoir dam in the foreseeable future and it can resume full filling of the reservoir.

The review found that the risk of the Ritschard Dam in Grand County failing is extremely low despite the deformation problems it has been experiencing.

“We’re a public agency and we’re pretty gratified that we’re not looking at a 30-plus-million-dollar fix right now,” River District spokesman Jim Pokrandt said.

The rock-fill, clay-core dam was completed in 1995. It has settled near its center by about 2 feet, a foot more than expected of it as an earthen dam.

Its crest also has moved about 8 inches downstream.

The district already has spent about $1.5 million to install instruments to measure the dam’s movement.

It has considered possible repairs ranging from injecting concrete into the dam to shore it up to rebuilding it. The latter is something the district several years ago estimated could cost $30 million.

The district is taxpayer-funded and includes Mesa County. Any repairs might have come at least partly out of a separate enterprise fund the district derives from revenues such as water sales.

The district has called the dam problem the most important issue it faces. The reservoir is on Muddy Creek, and the town of Kremmling is just downstream, where the Muddy meets the Colorado River.

The reservoir can hold about 66,000 acre-feet of water.

The district began to rethink how it should deal with the dam movement after a three-person outside team of dam experts said no immediate action was required.

In February, it then held a workshop on the matter with participants including, among others, the outside team of experts, the state Dam Safety branch of the Colorado Division of Water Resources and Denver Water, which has a leasehold interest in the reservoir.

Participants concluded that the risk of the dam failing from the movement in a given year is one in 100 million, compared to the normally acceptable one-in-a-million risk of the dam failing from a flood overtopping the dam.

“Thus, the deformation-
related public risk is much lower than other, normally acceptable dam-related risks,” the river district’s chief engineer, John Currier, said in a memo to the district board.

He wrote that the workshop participants concluded the chance of a dam failure from the problem is “very remote,” and that from a risk perspective “there is no compelling reason to proceed with remediation of the dam now or in the foreseeable future.”

“The dam is functioning properly, and has a very high probability of continuing to function properly even if deformation continues at the historical rate for many more years,” he wrote.

The district has been voluntarily keeping the water 10 feet below full as a precaution.

But those involved in the review agreed “that normal reservoir operation along with continued reasonable monitoring is appropriate,” Currier wrote, and that keeping water lower, while slowing down the dam’s deformation, merely prolongs how long it will take for that deformation to be complete.

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