Delaying the demolition of the 115-year-old LaPrele Dam near Douglas beyond April 1 would be a recipe for disaster, state engineers told Wyoming officials Thursday.
“We are at the point now where it (the dam) is actively failing,” Wyoming State Engineer Brandon Gebhart told the Legislature’s Select Water Committee.
Gebhart issued an order to breach the dam Nov. 1. He told the committee that he made that decision because there are no other options.
“I can assure you that if I failed to make the decision (to breach) and a dam failed, creating a catastrophe, killing people, I’m not sure I could live with that,” he said.
However, one rancher who relies on the dam for irrigation water and flood control asked if the 130-foot-high concrete structure can be given once last chance at extended life. The dam’s already 65 years beyond its original lifespan.
“What we would like to see, many of us, is to just keep this dam here and give it some time,” said Tomi Strock, whose family has ranched in the Douglas area for generations, told the committee.
She’s the Republican Wyoming House District 6 representative, but isn’t a member of the Select Water Committee.
If the dam is breached, there’s no telling how spring runoff could affect flooding along LaPrele Creek, she said.
“This creek has had a dam on it for 115 years,” she said. “We have no idea what the flooding is going to do with us — with the houses, the barns, corrals, everything — because we’ve had it there for so long.
“You take that (dam) out, we have absolutely no protection, nobody knows what it will do to us.”
Vibrations Killed The Dam
The dam was built in 1909, intended to have a 50-year lifespan.
It was evident that the dam had reached the end of its “useful life” in 2019, Gebhart said. An order was issued to draw the reservoir behind it down to a minimum level.
Engineers began monitoring cracks and other emerging problems with the dam.
Vibrations from huge releases of water though the dam’s outlets during the exceptionally wet spring of 2023 might have been what finally doomed LaPrele,engineering consultant Peter Rauch told the committee.
In early October, inspectors found a new, large crack above the dam’s outlet works. They also discovered that older cracks were worsening.
That came as a nasty shock, said Rauch, who works for the RESPEC engineering firm and has been a consultant on the LaPrele Dam project for years.
“There’s nothing we could have done to have prevented, ultimately, that scenario of high flow through the dam, vibration and cracking,” he said. “Nobody really saw that coming. We knew that the condition of the dam was bad. We hadn’t considered that it was so bad that it would start falling apart if we opened up the valves wide open.”
Patching the dam up with additional concrete so it can continue to hold only the bare minimum of water could cost $20 million to $21 million, Rauch said.
Demolishing it might cost $3 million to $4 million, he said.
Alternatives to get irrigation water to farms and ranches are being considered, such as pumping in water from the North Platte River system, Gebhart said.
Public Should Have Been Better Informed
Reiterating what other irrigators below the dam have said previously, Strock said that the breach order blindsided her.
There should have been public meetings and a chance for ranchers to voice their opinions before the decision was made, she said.
Gebhart said he mistakenly assumed that meetings engineers had with the LaPrele Irrigation District Board of Directors leading up to the order to breach were sufficient public meetings.
He told the committee that he vows to keep the public better informed in the future.
The committee voted to forward a bill that would set more protocols for issuing a breach order, such as requiring public meetings and sending written notice to water rights holders in advance.
The committee also forwarded a bill stating that, in the event of a dam breach, water rights would be protected for at least five years following the breach.
The full Legislature will consider both bills in its 2025 session.
Long-term solutions, including the potential to replace the dam, weren’t discussed at Thursday’s meeting.
Mark Heinz can be reached at mark@cowboystatedaily.com.
