LCRA crews will replace Wirtz Dam floodgates at Lake LBJ. Here’s why it matters to Austin
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Floodgates at Wirtz Dam, which forms Lake LBJ upstream from Austin on the Colorado River, will be replaced in a $76 million, three-year project, the Lower Colorado River Authority announced earlier this year.
If you’re new to Austin, you should know that the Highland Lakes are actually the Colorado River, separated by a series of dams. The LCRA, which runs the dams, uses them to manage the sometimes flood-swollen river and generate hydroelectric power.
On a side note: Lady Bird Lake is not one of the Highland Lakes. It is managed by the city of Austin.
So what does the LCRA’s renovation of floodgates mean for Central Texas, and how will it affect people in Austin? Here’s what we know:
What’s Wirtz Dam?
Wirtz Dam is one of the six dams on the Colorado River that form the Highland Lakes upstream from Austin. Think of the lakes as train cars carrying passengers, and when one car gets overloaded, the passengers move to the next car forward. Wirtz Dam connects Lake LBJ, which sits behind it, to the next car forward, Lake Marble Falls.
Wirtz was built in 1951 to create Lake LBJ, with nine gates to pass floodwaters downstream. The LCRA added a 10th gate in 1974 when the original Thomas C. Ferguson Power Plant was built nearby in Llano County.
Why is the LCRA replacing the floodgates?
According to the LCRA, the agency is upgrading each gate at Wirtz Dam “with a new custom-made floodgate that meets today’s engineering standards.” To keep the dam operating, the gates will be replaced one at a time.
“We could do this project more quickly if we replaced multiple floodgates at once, but we are in Flash Flood Alley, and that is not a viable option,” said John Hofmann, the LCRA’s executive vice president of water. “Dams along the Highland Lakes play a critical role in managing floodwaters, and we have to maintain their readiness at all times.”
The LCRA expects it will take about two months to replace each floodgate, which puts the completion date for the entire project sometime in 2025.
Will boaters still be able to use Lake LBJ?
Boaters will be allowed on Lake LBJ during the project, but the LCRA will expand the area that’s already off-limits to boaters from 150 feet to 300 feet upstream from Wirtz Dam. A buoy line will cordon off the construction area to give crews more room to work, the LCRA said.
How important are the floodgates?
Hofmann and the LCRA point out that Austin and other communities that cling to the sides of the Colorado River sit in the so-called Flash Flood Alley, which means we’re vulnerable to intense flooding because of steep terrain, shallow soil and very rapid rainfall rates.
“It’s important to note the dams were originally built to help tame the Colorado River after flooding time and again devastated the city of Austin and downstream communities,” Hofmann said.
While the LCRA was still securing federal funding to resume construction of Buchanan Dam in 1935, a June flood that struck the lower Colorado River basin also swept through downtown Austin. More floods followed in the late 1930s.
In 1957, ending a decadelong drought, floods forced the LCRA to open as many as six gates at Mansfield Dam on Lake Travis for the first time as part of flood management operations.
“Heavy rains here can quickly transform into walls of fast-moving water with great destructive potential,” Hofmann said. “Having operational floodgates on the dams allows us to manage flooding on the Colorado River by moving floodwaters downstream into Lake Travis, in which they can be temporarily stored until LCRA can release them in a controlled manner.”
The LCRA said the agency opens gates during flooding to move the water “in a more predictable and safe way,” adding that “without the floodgates, flooding would overtop the dams and threaten the integrity of the dams.”
Hofmann described the floodgates as “almost protective gear for the dams,” adding that they “allow us to have a rush of water come into a lake and continue downstream into the next lake without endangering the dam.”
When will the Wirtz Dam project start?
According to the LCRA, heavy equipment was arriving this month and installation of the first floodgate at Wirtz Dame is set to begin in April.
“The new 120,000-pound floodgates will be assembled in an area south of the dam, then moved to the dam via construction barges and cranes,” the LCRA said.
How does the LCRA pay for maintaining the dams?
Revenue from LCRA water customers pays for the maintenance on the dams for water supply lakes Travis and Buchanan.
LCRA wholesale power customers pay to maintain the pass-through lakes’ dams — Wirtz, Inks, Starcke and Tom Miller.
Will the LCRA renovate other dams?
Hofmann said the LCRA completed a similar floodgate replacement project at Tom Miller Dam in 2020 and a floodgate upgrade at Buchanan Dam in 2021.
“We also are in the midst of refurbishing floodgates at Mansfield Dam and are rehabilitating the cylinders that raise the floodgates at Starcke Dam,” he said. “We are continuously maintaining our dams, and we conduct regular testing to ensure they are ready to go when needed. We take care of our infrastructure to ensure it can take care of us when the time comes.”
The LCRA since fiscal year 2010 has invested more than $134 million in capital projects at the dams along the Highland Lakes, Lake Bastrop and Lake Fayette, the agency said.
“LCRA plans to invest more than $107 million in these types of projects over the next five years,” the agency said in a statement.
This article originally appeared on Austin American-Statesman: LCRA crews will replace Wirtz Dam floodgates at Lake LBJ. Here’s why it matters to Austin