Audio Engineer 
“The Bat Man and the Bridge Builder”
99% Invisible

“Mark Bloschock is an engineer from Texas, and in the late 1970s, he got a job with the Texas Department of Transportation renovating the Congress Avenue Bridge. The bridge was a simple concrete arch bridge that spans Lady Bird Lake in downtown Austin. It needed to be rebuilt with more contemporary beams called “box beams.” The box beams sit below the road’s surface, and they needed to be spaced a certain distance apart. Bloschock and the other engineers decided that the gap should be somewhere between ¾ of an inch and an inch and a half, which didn’t seem like a particularly meaningful decision… until the bats moved in.”

Original Air Date: February 23, 2021