Atlanta Int’l Combines Modular and Traditional Build Methods for Concourse D Expansion

Serving more than 100 million passengers annually, it’s no secret that Hartsfield-Jackson Atlanta International Airport (ATL) is a critical piece of the worldwide aviation network. So when the busy airport requires expansion or renovation, one of the biggest considerations is minimizing impact to operations. When it was determined that Concourse D, at 40+ years old, would require improvements to continue meeting current and future demand, officials recognized it would take innovation and creativity to make it happen.

Opened in 1980, Concourse D is one of five original concourses in ATL’s domestic terminal. It is the airport’s narrowest concourse, with a circulation corridor of 18 feet and holdroom seating for 5,400 passengers. The concourse was originally designed with 40 gates to handle 19 regional aircraft and 21 larger aircraft. But even after renovations over the decades, Concourse D remains dramatically undersized.

The current expansion program scheduled for completion in 2029 will:

• double holdroom size and increase seating to 6,400,
• widen the main corridor to 29 feet,
• raise the ceiling height,
• expand the boarding level by 75%,
• increase concessions options,
• double the size of restrooms, and
• add new building systems.

The width of Concourse D will be expanded from 60 feet wide to 99, and the new ceiling height will be up to 18 feet and taper down at the concourse edges to 14 feet to create more volume in the space. Additional glass on the walls will provide more ambient light, making the entire concourse brighter, airier and more open.

“Sixty feet may have been fine in 1980, but today it’s just so tightly packed,” relates Frank Rucker, ATL’s senior deputy general manager. “By greatly expanding the floor area, there’s more room for passengers to maneuver, and it’s going to be such a better passenger experience.”

When all is said and done, the concourse will include 34 aircraft positions, which is actually six fewer than before. The difference is that all will be for Group III aircraft, rather than a mix of Group II and III gates, so the overall capacity will be greater.

Cost for the game-changing expansion is estimated at $1.4 billion. The innovation and creativity that ATL officials knew would be needed is coming into play regarding the construction method. The project team is combining modular and traditional strategies, including the use of 19 prefabricated modules built on a six-acre lot adjacent to the airport. One by one, the completed modules are being transported across the airfield overnight to Concourse D for installation.

Preliminary Negotiations

The need to renovate or reconstruct Concourse D was identified in 2015 when ATL was in the process of negotiating airline leases. Leadership evaluated several expansion and/or redesign alternatives, and in 2016 narrowed the field to two options for further exploration and refining. In 2021, airport leaders chose a strategy that would use the existing structure, but refurbish and widen it.

In March 2022, project validation was completed and the construction manager at risk (Holder-Moody-Bryson-Sovereign joint venture) was brought on board to start preconstruction tasks, constructability reviews, phasing schedules and gate impact analysis. Because the original structure was built in the 1970s, the team knew a lot of work would be needed to meet current building codes, including updated seismic code requirements.

The operational impact of using a modular/traditional hybrid method was key to discussions about construction. Airport leaders had detailed conversations with tenants, particularly Delta Air Lines, regarding how many gates could be taken out of service at one time without causing extreme disruption. “It was a lot of volleying back and forth,” Rucker recalls.

The initial volley was ATL requesting half of the concourse, which would have meant demolishing and rebuilding 20 gates at one time. But that was met with a resounding “no.” The airlines lobbed back with a counter proposal involving just four gates at a time. That would have pushed the project completion date to 2031, which the airport felt was too long to wait for relief.  

In addition to considering how many gates the concourse could have out of commission at any given time, the project team had to factor in other facilities, such as restrooms and concessions. “You can’t run an airport without those things,” says Pete Pemantell, vice president of Operations for joint venture member Holder Construction. “It’s not just about holdrooms and passenger throughput; it’s passenger experience as well.”

Working collaboratively with stakeholders, the project team analyzed countless options to determine how many gates the airport could afford to lose without negatively impacting airline operations or the passenger experience. “When we were brought on board, not only were we studying which design to go with, we were also looking at different scenarios to find that sweet spot,” Pemantell explains. The goal was to facilitate efficient construction without financially impacting the airlines or compromising the passenger experience.

“Our main intent was to keep the existing building and existing operations as much as possible,” says Gopi Swaminathan, associate principal with project architect Corgan Aviation.

After working through several construction scenarios, the airlines and airport agreed to take eight gates out of service for construction at a time. To mitigate the operational impact of losing eight gates, ATL constructed three additional gates on the north end of Concourse E and transferred some of its low-cost carriers there. “That reduces the probability that we’ll need eight gates at a time,” Rucker says. “It’s probably more like a five-gate range, but we’re continuing to evaluate as we go through the project.”

The airport is funding the lion’s share of the $1.4 billion project with airline fees and passenger facility charges, in roughly a 50/50 split. A $40 million FAA Airport Terminals Program grant was secured to help offset the cost of the new Concourse E gates.

Out-of-Box Thinking

Rucker says ATL is fortunate to have creative minds on the project team that proposed using modular construction, but it wasn’t a decision the airport came to lightly. Leaders explored the idea extensively with the project architect and structural and mechanical engineers. A team also visited Dallas Fort Worth International Airport (DFW), which used modular construction for a four-gate expansion in 2022. “We came back fairly energized and said modular could be a component of the work,” Rucker recalls. 

[A full run-down of the DFW project is available online in the September 2022 issue of Airport Improvement magazine.]

“We wanted to deliver the building at a faster rate than what we usually do on a traditional development, so that is when the business case for modular construction started to make sense,” Swaminathan explains.

“We know it would be less costly to knock down half a concourse at a time,” adds Tom Nissalke, ATL’s assistant general manager of Planning and Development. However, that option would have had a greater impact on operations.

The prime benefit of combining modular and traditional construction is efficiency—modular pieces are created at a remote site while crews simultaneously work on the foundation and infrastructure pieces at the project site.

“We are an airport first, a construction site second,” Rucker emphasizes. “We have to consider the operations and the impact.”

“A lot of the focus was on how to mitigate the impact to airline operations,” Pemantell affirms. “With modular construction, you can hold off closing gates a lot longer because you’re starting the construction on a remote site.” That’s very attractive to airlines because of the decreased operational impact. 

From a logistics standpoint, modular construction allows work to occur off airport grounds, which means crew members do not need to go through security checkpoints to enter and exit the job site. Beyond saving contractors time, it increases productivity because work does not need to be scheduled around airline operations. Safety is also enhanced significantly because work does not occur on an active airfield. “You kind of work in your own little bubble and can control the construction a lot better that way,” says Pemantell.

Mod Squad

Expanding Concourse D is a complex project for the program manager, a joint venture of WSP, H.J. Russell & Company and Turner & Townsend.

“The integration of modular and typical sticks-and-bricks construction is a unique concept,” notes Chris Rogers, senior vice president of Aviation at WSP serving as program manager for the program management team. In addition, ATL’s high passenger and operations levels require extra coordination to make the hybrid approach a success.

To manage the complexities, the project team assembled a group of key stakeholders that meets regularly to collaborate, review and check/recheck project components. Established early in the planning process and dubbed the Mod Squad, this group was key in working through the design phase, initial engineering and plans for moving the modular units. “Initially, we were just talking conceptually, and then we had to start talking real technical details—the engineering from a structural side,” Pemantell relates.

The hybrid construction style requires more-than-usual planning and collaboration to ensure that materials are available and that both construction sites are in sync. “Those two jobs are working parallel and eventually have to meet somewhere,” he explains. “There are some logistical challenges trying to do all that on site and off site.”

For example, once the design of the modules was finished, decisions had to be made about how much outfitting would be completed prior to transport. Those discussions relied heavily on what building components could withstand moving across the busy airfield.

To help prepare for that complex operation, contractors performed extensive verification testing and practiced lifting one of the modular buildings with the same equipment that would later be used for the move. This allowed technicians to survey the structure with a laser scanner to check for changes.

Among other things, the test lift allowed architects to verify that materials installed, including the curtainwall system, didn’t incur any damage. Despite positive results, the test lift was just a lift, and not a move. So the team still collectively held its breath during the actual move. “It was a big win for all of us to see the module when it cleared the site and started moving toward the destination,” says Swaminathan. “We did not see any problems with the materials or the moves themselves.”

In addition to staging a test lift, the Mod Squad developed a 68-page “run of show” document. It included detailed logistics and a long list of contingency plans for the first move, and a minute-by-minute schedule for the days before and after. “We did not take moving across runways and taxiways at ATL lightly,” emphasizes Edmund Ramos, vice president of Project Management for WSP and deputy Concourse D project director. “We know that every minute shut down impacts efficiency.”

“We did our due diligence to prove we could move a building across the airfield,” adds Todd McClendon, the company’s senior vice president of Aviation for WSP and area director for Concourse D and E.

“By the time we got to the night of, our plan was dialed in, and everybody was ready to go,” Pemantell says.

All Systems Go

At 4:30 p.m. on April 23, the construction team held a “go/no-go” meeting, and by 5 p.m., it determined that everything was ready—equipment, weather, operations, etc. “Basically from that point on, it was all systems go,” recalls Pemantell.

Beginning at 12:15 a.m. on April 24, the first of 19 building modules began slowly making its way from the fabrication yard across the airfield to the terminal on a Mammoet self-propelled modular transporter. The large robotic vehicle was accompanied by a procession of lead vehicles with flashing lights, engineers walking alongside to monitor the load, a foreign object debris patrol team, and chase vehicles carrying tools, replacement parts and other contingency supplies. “After an hour and 15 minutes, we had made the full trek north and brought the module up to Concourse D,” reports Pemantell.

Mammoet’s huge transporters are built for precise and delicate movement, with full 360-degree motion. The vehicle positioned the module into place within 1/8th of an inch, parallel with Concourse D and the base plates over structural columns. “The last inches were the hardest,” Pemantell recalls. “Getting it exact was pretty tedious work.” Once the building module was positioned, crews laser scanned the building to make sure there were no structural issues. After that was verified, another team moved in to begin welding the columns to the base plates.

Phase 1 is made up of five modules that form an approximately 800-foot frame and were slated to be set in place at Concourse D at the end of May 2024. At that point, interior work will commence, including “stitching the structure together,” tying in utilities and installing passenger boarding bridges so that portion of the concourse can go live in September. Rucker notes that it will be a “rough finish,” as the final build-out cannot occur until the boarding level of the existing Concourse D is demolished.

The building modules weigh about 700 tons each and vary in size depending on where they will be located along the concourse. Their content also varies. Some have restrooms, while others contain concession space or gate areas. 

“They are tremendous structures in themselves,” says Rucker. Each frame is outfitted with as much of the electrical, IT infrastructure, HVAC ductwork, exterior cladding and windows as possible.

The timeline is aggressive, as the Phase 1 modules are scheduled to be anchored and welded in place onto the existing Concourse D. Within 90 days after the last of the five modules is set, the interior will need some finishing, but the addition is slated to be 100% complete from an exterior/gate standpoint. 

Like the module moves, the “90-day sprint” has a detailed playbook, and WSP is responsible for leading and coordinating the team to achieve the shared goal of opening the new gates this September.

Phase 2, which will extend Concourse D, is programmed to take about one year; phases 3 and 4 are scheduled to wrap up in fall 2027. These phases will combine modular and traditional construction. “It’s quite a complicated process,” Rucker remarks.

Once all the modular pieces are moved and the newly expanded Concourse D is weather-tight, crews will demolish and reconstruct most of the boarding and apron levels under the structure. Only the original apron-level columns will remain. In some areas, temporary systems will be deployed as parts and pieces of the new structure are added and the old systems are taken out of service.

Elevating the Passenger Experience

Rucker and other ATL leaders see the Concourse D Expansion as a unique opportunity to elevate the passenger experience. To achieve that goal, Corgan and the design team used benchmarking studies of other airports to determine the size of facility needed to achieve the airport’s desired service level. 

Swaminathan says that first and foremost, passengers want comfortable holdrooms and seating. Additionally, they expect volume, natural light and free movement across terminals and concourses. What they don’t want is to walk a lot. “It has to be a very comfortable place that you would prefer to spend time when waiting for the aircraft,” he says.

Passengers also expect a variety of nearby concessions, intuitive wayfinding and adequate and appropriate signage, he adds. “They want the journey to be as seamless as possible.”      

Prior to recent construction, Concourse D had 40 gates, with a mix of Group II and III designs. When the project is complete, it will have fewer gates—34—but the seat count will increase from 5,400 to 6,400 because all gates will be Group III.

Swaminathan describes the architecture of the building as efficient, and the transition from the existing Concourse D to the modular units as seamless. There are some challenges with pairing the two buildings, but he notes that design adjustments are being made to ensure the existing building will look as good as the new one. The newly expanded Concourse D is also designed to be more energy efficient and code-compliant.

Enabling projects included relocating the sanitary sewer and adding a new branch of main water and a telecom duct bank. “We had to essentially relocate those site utilities because they were under where the new addition would be,” Pemantell explains. Moving the utilities farther away from the building opened a 30-foot space and allowed the construction team to “really start flowing into the main project.” Additionally, some exits had to be relocated and new stairs constructed to meet code requirements before the first eight gates were closed. 

Harbinger Project

Following the first move of modular pieces, ATL’s Nissalke reports that the airport team is extremely pleased with the process and expects subsequent moves will include the same level of rigor and focus.

“The team did an excellent job of thinking through every aspect,” agrees Rucker. “We’re not out here to not achieve excellence.”

The Concourse D project shows that modular construction and/or a hybrid of modular and traditional is a viable way to expand existing facilities, he adds.

Rogers, of WSP, considers modular construction a “game changer” and expects more airports to consider it.

His colleague McClendon agrees, adding, “I’d tell any client not to shy away from this delivery method. Anything you can do landside is a huge benefit. We’ve seen the value.”

Pemantell feels that modular construction makes sense for many airports. “Not every project lends itself to modularity like this one did, but I think it’s becoming a lot more feasible for more airports. I think it’s the future of aviation construction.”

Now that the project team is comfortable with modular systems and how they respond to a move, Swaminathan says there are discussions on how progressive project designers can be with future construction. “If the buildings or phasing would allow us to push the building to be more complete, we want to take that approach and try to add as much as possible in the module to reduce downtime on the actual site,” he explains.

Ramos emphasizes that the quality and workmanship of the Concourse D extension will help dispel the negative stereotypes many people have about prefabricated buildings. “We’ve been able to demonstrate that we can ensure a higher quality project because it’s built off site, and we’re not constrained by operations or space,” he explains.

Modular construction uses standard, tried-and-true materials, notes McClendon. “There’s not a single material that we’re using that’s not part of our standard kit of parts—from the roofing to the glass to the metal exterior to the ceilings on the inside. We did not compromise our standards to support the modular concept.”

The willingness even to explore an alternative construction method should be commended, McClendon adds. “The collaboration among the Department of Aviation and the carriers to see this project happen gave us the tools to go out and figure out the best way to do it.” 

For the Concourse D expansion, the best way just happened to include modular construction.