By LYNETTE HAALAND
Four Points News
Mansfield Dam is undergoing a decade-long, $10 million-plus maintenance project which includes taking out each of its 24 floodgates to repair — something that has never been done in the dam’s 75-year history.
Built between 1937 and 1942, Mansfield Dam is 278 feet tall and the tallest dam in Texas. The dam created Lake Travis and protects Austin from flooding.
Mansfield Dam’s 24 floodgates are showing signs of corrosion and deterioration.
“It’s time to take them out and completely refurbish them. There is corrosion due to humidity and water,” said John Hofmann, executive vice president for water at Lower Colorado River Authority.
The $10 million-plus project was launched in late 2014 and is expected to be completed in 2025, Hofmann said.
Crews have completed five of the 24 floodgates and are working on two right now.
They work on one or two gates at a time to stay at “flood-ready status 24/7.” Hofmann said.
These repairs do not affect emergency operations during heavy rains.
“The most floodgates we have ever had open at one time was six back during the 1991 Christmas floods,” he said.
It takes LCRA crews six months or so to work on one floodgate, and it costs more than $500,000 to refurbish each gate.
The floodgate repairs start approximately 150 feet below the surface of Lake Travis in a long tunnel. In order to remove each floodgate, and outer gate closes it off from Lake Travis. Then a hoist lifts the huge, 50,000-pound gate out of its place. It is put on a cart that is on rail tracks, and then five to six LCRA workers manually push the gate down the tracks.
When the gate comes out from the dam, crews refurbish its more than 5,500 individual pieces, each designed with hand drawn blueprints from the late 1930s.
Floodgate motors are sent offsite to be refurbished and LCRA crews clean and replace other parts. Each gate is fully tested before being hauled back through the dam’s tunnel and put back into place, Hofmann said.