A weak spot near the low-water dam that forms Lake Brazos through downtown Waco is expected to cost $9.1 million in repairs that are expected to begin in the fall.
If the earth embankment on the east bank near the low-water dam were to fail, the river could largely bypass the dam, causing the water level to drop across the city. The city has reinforced the embankment with steel, rockfill and other materials over time, but it has needed reinforcement since the dam was built in 2007, officials said. Utilities director Lisa Tyer said the project is tentatively set to start in October and finish in 2025.
The Waco City Council voted Tuesday to approve a contract with McMillen LCC for the $9.1 million project, after a detailed presentation by Freese and Nichols engineers and city utility officials.
“That dam is really what makes your town a lake,” said Freese and Nichols engineer Victor Vasquez. “If you lose that fill, you lose the lake, and the cost of repair is significant if that were to happen.”
People also read…
Waco City Manager Bradley Ford touted the article as a “beautiful presentation of the dam” that elicited laughter, groans and at least one “oh come on” from the audience, mostly the staff of the city.
Vasquez, who has previously spoken to council on the subject, said Freese and Nichols do not know how the embankment was first constructed in 1985.
“The structure is standing, but the fact is you have a risk of failure here if the conditions are right,” he said.
About $7 million of the construction costs will come from water bonds the city issued last year, and the remaining $2 million will come from the water department’s capital improvement program plan.
Vasquez said the city first built a dam on the site in 1970, then modified it in 1985 because it was likely to be blocked by brush and logs with every heavy rain. The city replaced it entirely in 2007 with a labyrinth weir design suggested by the US Army Corps of Engineers.
Freese and Nichols designed the new dam. In the final stage of the project, the Brazos River flooded and damaged the earth embankment, removing a noticeable portion of its slope which was still clearly visible in the current photos included in the presentation.
The Waco City Council voted against rebuilding the embankment when the dam was built, and the embankment continued to suffer damage during floods in 2015, 2016 and 2018, according to the city. In 2017, Freese and Nichols assessed the embankment, found it unstable, and recommended repairing it.
Tyer said a sinkhole appeared in the embankment in 2019 and Deputy Director of Utilities Charles Leist stayed awake overnight until the city repaired the damage.
The project will also include the reconstruction of the dam outlet structures, which divert water for dam maintenance. Elements of the outlet structures cross the embankment being repaired.
The east side outlet works were built by local engineer FM Young as a diversion system he wanted to use to generate hydroelectric power.
“It never materialized, but it added a nice feature to the play-off,” Vasquez said.
Reconstruction of the east side outlet will involve replacing steel pipes, creating a new concrete basin and moving some of the infrastructure to a higher elevation to prevent it from collapsing. collapses during floods.