Six deepwater support columns for a new U.S. Highway 378 bridge over Thurmond Lake must be rebuilt using a new design, according to the Georgia Department of Transportation.
Construction on the 1,680-foot span between Lincolnton, Ga., and McCormick, S.C., began in April 2010 but was halted last year after anomalies were detected in underwater support columns.
After a lengthy investigation, experts concluded the columns, anchored beneath as much as 80 feet of water, were impacted by a rare chemical reaction – known as “delayed ettringite formation,” or DEF – which can occur when poured concrete overheats while curing.
“DEF is rare and there is no record of it ever having occurred on a bridge project in Georgia,” said DOT spokeswoman Cissy McNure. “DEF can, however, result in weakening and cracking of the concrete. Consequently, Georgia DOT decided six existing columns for the new bridge should be rebuilt using a new design that will be incorporated on the entire project.”
The redesign will be completed within a month, after which a revised work schedule will be developed, she said.
The latest project budget – $22.4 million – is about $6 million more than the original contract.
McNure said new cost estimates have not been prepared.
“We don’t have all the details yet as far as a new completion date and a new cost amount, but we do know what the final findings were,” she said.
Meanwhile, workers resumed construction Monday on other parts of the project, so motorists in that area might experience short delays during intermittent single lane closures.
The contractor is Alabama-based Scott Bridge Co., which also managed the $192 million construction of the Interstate 20/Bobby Jones Expressway juncture in Augusta.
Once completed, the new concrete bridge will be 44 feet wide to accommodate two travel lanes and two emergency lanes. At its highest point, it will stand 36 yards above the lake at full pool.