NORMAN — LEXINGTON –– Repairs for the US-77/State Highway 39 bridge connecting Lexington and Purcell are ahead of schedule, ODOT officials said Thursday.
Rep. Bobby Cleveland toured the bridge Thursday with several Oklahoma Department of Transportation and Slaughterville officials.
ODOT Chief Engineer Casey Shell walked everyone through the chain of events leading to the closure of the bridge, which is scheduled to open June 14. The contractors working on the bridge will receive incentives if the bridge is completed before that date or penalties for every day after June 14.
In January, ODOT contracted a company to make repairs involving welding brackets on the bridge. Shell said neither the contracted company nor ODOT knew the base of the bridge was made with a manganese alloy.
It is the only bridge in the state built with manganese alloy, and experts classified the manganese as an “exotic metal” that is not common in bridges, Shell said.
The welds caused the manganese to become brittle and cracks formed, which they thought at the time was due to the tightening of tension rods, Shell said. After further inspection, it was discovered it wasn’t the tension but delayed hydrogen cracks that would’ve cracked eventually.
During an annual inspection of the bridge shortly after the welding project was finished, Shell said the cracks, which were isolated around the welded brackets, were found and a weight limit of five tons was set for the bridge, allowing only passenger vehicles to cross.
The next day, crews went out to measure and get dimensions, at which time the weight limit was changed to 16 tons to let emergency vehicles and school buses cross the bridge. At that time, more cracks were discovered, so ODOT called in experts to inspect the bridge, Shell said.
“At that point, we were suspicious that something was going on,” he said. “They said, ‘We need to close this bridge immediately.’”