When HNTB founder Ernest Howard built the bridge in 1910 over the Colorado River linking North and South Congress Avenue in Austin, Texas, he was thinking in terms of Model A cars and horse carriages that would use the structure. But when it came time in 1981 to prepare the bridge and its foundation for V6 engines and buses, the Howard foundation design proved able to support the changes.
The Congress Avenue Bridge, design by HNTB founder Ernest Howard, opened in April 1910. Photo: HNTB
A highway department didn’t exist when the Congress Avenue Bridge was built. Congress was a state highway stretching from Austin to San Antonio. In building Congress Avenue Bridge (renamed in 2006 the Ann W. Richards Congress Avenue Bridge), which opened in April 1910, the governor wanted a bridge that wouldn’t wash out with the next flood.
In 1981, Richard Ridings (now of HNTB) was assistant public works director for the City of Austin and was tasked with addressing the Congress Avenue bridge. His first thought was to implode it because it had reached the end of its planned life. However, forensic analysis revealed that the foundation was “incredible.” It was clear that “someone had designed it with the long term in mind.”
As a structural engineer, Ridings was impressed by the thoughtfulness of the design and beauty of the bridge. More than 100 years later, those foundations are still there, which is rare in growing cities. Such bridges typically are widened and reconstructed every 75 years.
Only one small section of the structure needed repair. The deck was expanded off of the original base and sidewalks were added. At the time of the update, the arch of the deck was changed, leaving openings between the beams, which is where the famous Congress Avenue bats now live. Previously, they lived in the cracks and crevices of a broken storm sewer pipe under Congress Ave., which was repaired around the same time.
According to Bat Conservation International, the Ann W. Richards Congress Avenue Bridge is now home to the world’s largest urban bat colony — as many as 1.5 million Mexican free-tailed bats emerge nightly (http://batcon.org/index.php/get-involved/visit-a-bat-location/congress-avenue-bridge.html).
Congress Avenue Bridge history and photos provided by HNTB (www.hntb.com). Send information about historical civil and structural engineering projects and engineers to Bob Drake at firstname.lastname@example.org.
Construction of the Congress Avenue Bridge in Austin, Texas. Photo: HNTB