DADE COUNTY, Ga. — Georgia transportation planners have finished a revolutionary construction project unlike any in the nation. And it has nothing to do with the I-85 collapse.
It's two and a half million pounds of new steel and concrete in the form of a new bridge in Dade County.
It was installed over a single weekend while interstate traffic continued to flow underneath.
Georgia Department of Transportation officials say they'll apply some of the lessons learned to a crucial project in downtown Atlanta.
Channel 2 consumer investigator Jim Strickland was there when a team of inspectors combed over the new State Route 299 overpass.
In a first-of-its-kind engineering feat, contractors built it using a technique called "accelerated bridge construction.”
"This is the first time Georgia has done a full A.B.C. project. And what we did was we moved the bridge into place in one weekend," Andrew Hoenig, with GDOT, told Strickland.
The new bridge was built on-site, just north of the 50-year-old one needing replacement.
A time-lapse video taken by GDOT showed what happened next. After demolishing the old bridge, giant movers -- each with 100 wheels to handle the weight -- slid the entire new bridge into place. It took a total of only 81 hours.
"That weekend we closed 299 and actually moved the eastbound side first, and then we moved the westbound side. This is the first time, we think, in the country where they did two moves over live traffic in one weekend," Hoenig said.
The key was keeping I-24 open. The stretch of highway below the bridge handles 65,000 vehicles a day with one in four vehicles being a semi-truck.
County executive Ted Rumley says closing 299 for little more than three days was also vital. Handling the project normally may have meant a yearlong detour away from small businesses along the route.
"If they would have shut it down, even another week or so, every 24 hours, it's tremendous the loss that these people here would take," Rumley told Strickland.
Residents Madge and Bob Boggild witnessed the entire process from their car. They take the bridge twice a week.
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"What drew you to come and watch everyday?" Strickland asked the Boggilds.
"Well, because it was new and it was different," Madge Boggild said.
Workers eventually permitted them to be the first to drive over the new bridge.
"It was exciting," Madge Boggild said.
"And what time of day was it?" Strickland asked.
"2:30 a.m.," Boggild said.
The completion ran about 25 hours behind the already break neck schedule.
One of the challenges was getting the movers synched up. The bridge, with its curved span and four-degree pitch, required an especially precise fit.
"When you build it off site and match it, you've got to be right," Rumley told Strickland
Certain elements of A.B.C. construction are expected to speed replacement of the Courtland Avenue bridge over the connector next year.
But state planners say the full technique is best applied in rural areas where there's room to build the new bridge first before moving it. As successful as this project was, metro Atlanta won't see a lot of them.
"I think one a year is probably a good assessment, so over the next five years, maybe five or six," Hoenig said.
In Dade County, they're proud to have been the test case. And happy it worked.
"It's a relief," Rumley told Strickland.
The bridge cost $7.3 million. But GDOT officials say not having to buy land to put in a detour and not having to burden the local economy with a lengthy road closure amounted to huge savings.
Cox Media Group