Discovery of caves forces TxDOT to delay La Crosse Avenue bridge project


AUSTIN (KXAN) — The MoPac Expressway in south Austin has been under construction for more than a year now, and KXAN learned the La Crosse Avenue bridge project is being delayed.

The bridge is part of a bigger MoPac improvements project, which began in January 2018.

Jennifer Archambeault whose house backs up to Mopac told KXAN it’s been a long year and half, living next to the construction site. “18 months! There’s rocks everywhere. There’s dirt everywhere, so our cars are always dirty, but that’s the least of our worry. Our house has shaken so much our tiles have broken in six areas.”

The Texas Department of Transportation recently opened a new diverging diamond intersection on the Slaughter Lane overpass, and right now, it is working on the La Crosse Avenue overpass.

However, the La Crosse Avenue bridge, which has been closed since the end of March, will take a few more months to build than TxDOT originally planned because crews discovered dozens of caves.

A karst feature discovered at the Mopac and La Crosse Avenue construction site.

TxDOT explained, construction has been ongoing, but every time a new feature is discovered, they have to pause in order to evaluate and develop a mitigation plan.

Each feature requires its own plan to minimize potential adverse impacts to the aquifer. The Texas Commission on Environmental Quality said TCEQ has already reviewed and approved several mitigation plans.

A karst feature discovered at the Mopac and La Crosse Avenue construction site.

Bobby Levinski, attorney for Save Our Springs Alliance, said TxDOT should’ve seen this coming.

“Even before construction, they knew that they would likely encounter caves,” he said. “I think that’s part of the problem. They kind of dismissed the prevalence of those caves.”

Levinski said water in these caves eventually make its way to Barton Creek.

“If there’s contaminants that are going into the caves there, within two days, it would show up at Barton Springs Pool,” he explained. “Barton Springs is our future drinking water supply for the city so we want to be very careful to protect it.”

Levinski said this is an area with a lot of caves, so TxDOT is likely to encounter more karst features going forward.

“Hopefully they can learn from the experience of the South MoPac project and look at the design they’re doing for the Oak Hill Parkway and mitigate those concerns in advance,” he said.

A map illustrates how recharge features in this area are on a direct path towards Barton Springs, according to Save Our Springs Alliance. (Barton Springs Edwards Aquifer District Photo)

Archambeault said she wishes the delays could’ve been prevented to begin with, but as construction continues, she hopes TxDOT will communicate better with residents and put up more signs to warn drivers about traffic pattern changes.

“We hear loud crashes all the time because someone wasn’t paying attention,” she said. “We just want to get to our home in one piece and we want to get there timely.”

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