A major part of setting the foundation for the new Clarks Bridge in Gainesville was finished Thursday.
As storm clouds gathered, the Georgia Department of Transportation poured the last of 12 caissons across what will be the 952-foot structure spanning the Chattahoochee River on Lake Lanier.
Crew members directed traffic on Ga. 284/Clarks Bridge Road, as a lane closure was required for the effort.
The caissons are vertical supports that tie into bedrock between 95 and 107 feet deep, DOT district spokeswoman Teri Pope said.
The next phase — the laying of horizontal caps tying the caissons together — is already underway. Two of six caps have been poured.
Bridge beams then will be put in place, running longways across the caps, Pope said.
“After all beams are in place, then (workers will) weld steel plates between beams and fill pans with concrete, creating one structure,” she said.
The entire project is set for completion by Dec. 31, 2015.
“Bridges are the most complicated structure we build, and they take the longest to build,” Pope said.
The good news for motorists is switching traffic from the old bridge to the new one will happen literally overnight.
“Once the new bridge is built, we’ll be able to pace traffic overnight, and the next morning, (all motorists) will be using the new bridge,” she said. “There won’t have to be a detour or closure to tie in the new bridge.”
Two crews will be working this summer — one to build the bridge and the other to build a 63-foot pedestrian tunnel, which will run under Ga. 284 at the Lake Lanier Olympic Venue.
With digging underway, Ga. 284’s grade must be raised by 3 feet to accommodate the concrete tunnel, which will be 10 feet wide and 8 feet high.
The tunnel and grade work prompted the DOT to close Ga. 284 from Clermont south to the venue to through traffic.
The road segment is set to reopen by July 26.
Motorists will be able to reach the venue by traveling north on Ga. 284 from U.S. 129/Limestone Parkway, as the bridge will remain open. To access the parking and boat ramps at Clarks Bridge Park, vehicles must travel Ga. 284 northbound.
The DOT’s detour route involves only state routes: Ga. 284, Ga. 11/U.S. 129/Cleveland Highway and Ga. 52/Brookton-Lula Road. There are several local connections between Ga. 284 and U.S. 129, including Lakeland and Honeysuckle roads.
“We are monitoring traffic flow at each signalized intersection along the detour route and will make changes to the signal timings ... as motorists get used to the detour,” District Engineer Bayne Smith said.
“Usually the first week of a detour is a learning curve, then backups dissipate as people choose their personal detour route.”
The road closure is taking place in the summer so as not to affect school travel, Pope has said.
The entire project costs $8.7 million. Clarks Bridge, built in 1958, doesn’t meet current design standards.