What began as a routine overnight construction closure of southbound I-59/20 in downtown Birmingham, Ala., turned into a weeklong outage when an incomplete steel girder system shifted atop its temporary support structures.

On April 4, workers from Granite Construction Co. were installing 9.5-ft-tall, 65-ton girders for a new bridge at the I-65 interchange, part of the Alabama Dept. of Transportation’s three-phase, $750-million upgrade of I-59/20’s 45-year-old infrastructure. According to a Granite spokesperson, four girders being readied for splicing in the middle of the interchange were supported by two standard 100-kip shoring towers with 100 kip-per-leg capacity. The towers were erected on crane mats with welded steel stringer beams on the top and bottom. ALDOT says an apparent partial failure in one of the supports caused the girders to shift approximately 1 ft laterally and between 6 in. and 12 in. vertically.

Granite and ALDOT developed a strategy to stabilize and reset the girders in their permanent position. But the plan required the location, delivery and setup of a 400-ton Liebherr crane. Rain events on Friday and Saturday required the crane to be reset to assure its integrity, according to the Granite spokesperson. Granite was able to stabilize and place the slipped girders, and safely completed the splicing work. By the afternoon of Wednesday, April 11, the crane had been removed and I-59/20 reopened to traffic. The cause of the shift remains under investigation. Granite’s contract calls for a $500,000 fine for each day I-59/20 was closed. The company says that the incident will not affect the scheduled completion of the new I-65 interchange ramps later this year, as additional girders were placed during the outage, eliminating at least three planned overnight lane closures.

More than 160,000 vehicles a day travel I-59/20 through Birmingham, twice the highway’s original design capacity. The upgrade program is scheduled for completion in late 2020.