The Texas Department of Transportation will begin one of Austin’s largest underground construction projects in 2026—boring 6.5 miles of 22-foot-wide tunnels beneath I-35 to reduce flooding along the corridor.
Explained: As part of the I-35 Central project, the tunnels—large enough to fit a CapMetro bus—will stretch from 45th Street to Cesar Chavez Street before turning east toward U.S. 183 near Lady Bird Lake. Work will begin with excavation of nine drop shafts up to 200 feet deep, with the first tunnel boring machine starting near Airport Boulevard in 2026.
The $748 million project, led by contractor Sak & Shea, also includes a new pump station capable of treating 130,000 gallons of stormwater per minute. TxDOT says the system will improve water quality, lower the floodplain by roughly 350 acres and ease pressure on the Waller Creek tunnel.
Looking ahead: Construction will run around the clock through 2029. Nearby residents can expect some vibration and dust, though TxDOT plans to monitor and mitigate both throughout the project.