Construction on the massive I-285/Ga. 400 interchange project likely will begin just four months from now in mid-October, state Department of Transportation project manager Butch Welch said at the June 14 meeting of the Buckhead 50 Club.

Welch and GDOT communications manager Jill Goldberg gave an update on the 284/400 project, slated to wrap up in mid-2020, at American Legion Post 140 in Chastain Park. The project remains the same, but there were some new details and explanations of such lingering mysteries as traffic impacts and the contractor team’s surprisingly low bid.

The 285/400 project and other GDOT plans got a skeptical response from members of the civic and social club. “In general, you build more roads, you get more traffic,” one audience member said.

Goldberg said GDOT is no longer adding regular lanes to highways. Instead, it will add “managed lanes”—express lanes where drivers pay a toll that changes based on traffic volume. Managed lanes on I-75 in Cobb County are under construction now, and more are coming, eventually including 285. “Someday, the whole Perimeter will be connected by managed lanes,” Goldberg said.

Welch noted safety is another reason for the project, as the interchange currently forces drivers to change lanes rapidly to enter or exit. He said he’s surprised there aren’t more accidents, adding, “I was involved in one [accident] two months ago.”

Besides rebuilding the interchange, the project also adds “collector-distributor lanes”—physically separated exit and entrance lanes—to 400 north to Sandy Springs’ Spalding Drive and to 285 between Sandy Springs’ Roswell Road and Ashford-Dunwoody Road in Dunwoody and Brookhaven. The 400/Abernathy Road interchange in Sandy Springs will be rebuilt as a “diverging diamond,” where traffic flow directions change in time with traffic lights to move cars through faster.

Some other details from the meeting:

GDOT, contractors will be nearby

GDOT and the contracting team, North Perimeter Contractors, will soon open field offices within walking distance of the project, on Carpenter Drive in Sandy Springs. That street is just north of the 285/Roswell Road interchange. Carpenter is also about to get its own major city construction project.

Traffic could improve during construction

Welch said the project will have “minimal traffic disruptions”—a relative term—with most of the work taking place at night. He also said traffic should improve during construction because various ramps and lanes will open as they are finished, instead of shutting the whole interchange down and reopening it all at once. “I think as the project progresses, you’re going to be seeing just more freedom of movement through the corridor,” Welch said of the phased-opening plan.

As for impacts on nearby Buckhead, Welch said it’s “hard to say.” Goldberg said some cut-through traffic is likely as drivers “get scared” by the project, but most of the work will be at night.

GDOT is planning a system of regular, real-time construction and detour updates for the project.

It takes a lot of material

Welch gave some construction supply numbers:

33 bridges will be built or rehabbed.

More than 1 million square feet of noise-blocking walls will be built, and a similar amount of retaining walls. The noise walls will be concrete facing on a foam core. They will replace all existing noise walls, which Welch said some people describe as “trailer park” in appearance.

It will take 400,000 tons of asphalt to pave the I-285 section and 2 million square feet of concrete paving on Ga. 400.

125,000 linear feet of storm drains will be installed.

Why the bid was so low

GDOT estimated the project budget at $803 million, while North Perimeter’s winning bid was only $460 million. Less expensive is good, but the bid was so surprisingly lower that GDOT staff spent two days reviewing it in detail for flaws, Goldberg said after the meeting. She said the contractors actually improved the plan and found “efficiences” in design and right of way use, and especially “saved tremendously on financing”—GDOT is using a method where the contractor finances most of it. (The actual price tag will be higher when previous right of way acquisition and other work is factored in.)

“We feel very confident and secure with that bid” and that it won’t go up significantly later, Goldberg said.

The audience was skeptical

With the population booming, a Braves stadium coming soon to nearby Cobb County and public transit expansion lagging, Buckhead 50 Club members were skeptical that road work will decongest anything for long. Managed lanes will make things “worse for the masses” who can’t afford the tolls, one man said, while others talked about the lack of MARTA expansion and the unbuilt Outer Perimeter highway to handle truck traffic.

“I see the symptoms being worked on, not the cause,” said Jim Duffie, a Republican candidate currently in a runoff with Lane Flynn in DeKalb County’s House District 81, a seat held by incumbent Democrat Scott Holcomb. The district does not cover the 285/400 area, but it does include part of Brookhaven, and Duffie said he is a proponent of running a monorail line in the Perimeter Center and Buford Highway areas.

Goldberg said GDOT’s projects are tightly limited by state law, which prevents funding mass transit and requires the department to have an entire project’s budget in cash before starting construction. The 285/400 deal, where the contractor undertakes the bulk of the financing and thus speeds up the work, is one innovation GDOT is trying, she said.

GDOT has an animated video overview of the 285/400 project: