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KUIf you’ve been driving on I-35 through Central Austin, you may have noticed tall construction walls going up at certain points along the highway and wondered what’s going on behind them.
Those barriers are designed to block the sound of machines digging deep holes called drop shafts for one of the largest tunnel projects in Austin history.
The tunnel is so large that building it will cause the ground to vibrate along its 6.5-mile path down I-35 and East Cesar Chavez Street, creating uncertainty about the risks to nearby structures.
The drainage tunnel is required to prevent I-35 from becoming a raging river during rush hour rains. As part of a major expansion of the highway through Travis County, the Texas Department of Transportation is dropping the main lanes up to 60 feet below ground level from Holly Street to Airport Boulevard.
Those sunken main lanes, parts of which could be covered with giant decks by the city of Austin, will allow a clear view across the highway for the first time since it opened in 1962.
The lowered lanes will also serve as troughs for Austin’s notoriously drenching rains when the sky opens up. So the 22-foot-wide tunnel will send that stormwater streaming to the Colorado River downstream of Lady Bird Lake.
One tunneling machine will start near I-35 at Airport Boulevard and drill south. Another will tunnel west under Cesar Chavez Street from near U.S. 183. The machines, working at a depth of up to 200 feet, will meet near Cesar Chavez and I-35.
Besides the environmental concerns around such a large drainage project — like the air and noise pollution from trucks hauling excavated rocks and dirt 24/7, or routing the waters of Boggy Creek west of I-35 into the drainage tunnel, or pumping thousands of gallons of treated highway runoff into the Colorado River — the construction itself will rattle a lot more than nerves.
Tap the link in our bio to read more from Nathan Bernier.
Video produced by @KUTNathan
Video sources: Nathan Bernier, TxDOT and Herrenknecht
@kut_austin
