San Francisco Int’l Adds Interim Corridor to Preserve Passenger Experience During Terminal Modernization

San Francisco International Airport (SFO) is quite literally raising the bar for passenger safety, comfort and convenience during construction. As part of its $2.6 billion Terminal 3 West Modernization project, the California airport recently opened an interim corridor elevated approximately 17 feet above the tarmac. One of its primary purposes is to keep travelers flowing smoothly to and from their gates throughout upcoming years of construction inside the nearby terminal.

Instead of installing a standard passageway, SFO opted for a more deluxe version filled with natural light, brightly colored graphics and wayfinding elements that coordinate with the airport’s other signage. “It’s a more enjoyable connection experience,” remarks Julia Katz, program manager for the Terminal 3 West Modernization Program.

The West Interim Passenger Corridor includes two sections. The first, spanning 440 feet, starts near Gate E2 in Terminal 3 and ends at the rotunda food court near the F gates in the same terminal. The second section stretches 1,000 feet, extending from the F gates food court to an existing post-security walkway that leads to the international Terminal G gates. Both opened in early November, just before the busy 2024 holiday travel season began.

facts&figures Project: Interim Corridor Location: San Francisco Int’l Airport Total Length: 1,440 ft. Cost: $40 million Funding: General revenue bonds Construction: Feb. 2024–Nov. 2024 Key Components: 2 corridor sections—440 ft. & 1,000 ft.—made from 11 prefabricated modules Design-Build Team: Turner Construction Co., with Gensler and TEF Design joint venture Structural Design: Magnusson Klemencic Associates Mechanical Engineering: Southland Foundation Engineer: OLMM Consulting Engineers Special Systems & Electrical: Rosendin Corridor Ceilings: Armstrong Ultima Tegular 24×24-in. acoustical panel ceilings Key Benefits: Improved passenger flow; enhanced passenger safety; cost & time savings; streamlined construction phases; better passenger experience during construction

Maintaining passenger access to boarding areas while overhauling Terminal 3 West posed a complex challenge for the airport and its project team. If SFO hadn’t added the enclosed corridor just outside the terminal, passengers would have been repeatedly rerouted around active construction areas through interior tunnels with only artificial light. Contractors rebuilding the terminal would have had to build a new passageway each time they completed another phase, likely extending the construction schedule and increasing costs. The elevated corridor keeps passengers completely outside the construction areas by routing them around the existing building. Providing a single, consistent route minimizes disruptions, enhances safety and improves the overall travel experience.

The $40 million it cost to add the interim corridor was fully offset by savings associated with eliminating the need to build and rebuild interior tunnels, reducing construction phases and completing the terminal modernization more quickly. “You have cost and schedule efficiencies just from being able to capture more of the job site and do that work in one big chunk,” Katz notes. Consolidating the work area and allowing construction to proceed in uninterrupted phases enables the overall Terminal 3 West project to move forward more effectively, efficiently and safely because passengers are kept out of the construction area.

Airport leaders selected Turner Construction Company, with the Gensler and TEF Design joint venture, to execute the design-build project. Magnusson Klemencic Associates provided structural design services for the interim corridor project as engineer of record for the Terminal 3 West Modernization.

Dismissed Idea to Embraced Solution

During the Terminal 3 West Modernization, SFO is renovating 650,000 square feet of space in one of its busiest terminals. The project will include a seismic retrofit, security checkpoint expansion and additional passenger amenities. A 200,000-square-foot expansion with new food, beverage and retail concessions is slated to open in late 2027.

Making these massive changes presents significant logistical hurdles, especially for United Airlines operations in boarding areas D, E, F and G, which must remain accessible throughout renovations. “Because of that, the project as a whole is going to be highly phased,” says Katz. “In order to minimize those phases and get some construction efficiency, we came up with this concept of doing what we call ‘interim corridors’ to route people around the first phase of the project.”

The idea was hatched early in the planning process and refined over time. Initially, it was dismissed as too costly. Then, the COVID-19 pandemic forced a three-year pause in the Terminal 3 West Modernization. The project team built a strong business case, showing the corridor would save both time and money, and the concept was eventually embraced.

Together, SFO, its design-build team opted for a prefabricated structure to streamline construction. The structure was designed to support a live load of 100 pounds per square foot to accommodate passengers, pallet jacks for transporting goods and small service vehicles, notes Terry Palmer, aviation market leader for Magnusson Klemencic Associates and its principal in charge of structural design for the Terminal 3 West Modernization project. The lateral walkways were engineered to withstand high winds and seismic forces prevalent in San Francisco.

Passenger-Centric Details

As the interim corridor concept developed, SFO’s team prioritized the passenger experience. “We didn’t want this to feel like just a temporary construction barrier corridor for travelers,” says Ryan Fetters, a Gensler principal. “This is going to be their experience at the terminal for the next two and a half years.”

Natural light helps the interim corridor feel less temporary for passengers.

To ensure passenger flow remains smooth and congestion-free, the corridor was designed as a transit-only space with no seating or amenities. Its purpose is to provide a safe, efficient route to other areas with amenities. “We want people to get in these corridors and have a good experience in them but get through them as quickly as they can, so we’re not making their travel any longer,” Fetters explains.

“Passengers are able to walk comfortably and enjoy the experience as they traverse to and from their airplanes—an essential requirement at SFO,” adds Pablo Echeverria Garcia, senior design engineer with Magnusson Klemencic Associates and the firm’s lead structural designer of the interim corridors.

The design teams carefully evaluated the width and operational needs of the spaces and also took into account SFO’s robust wayfinding program. Large portal elements were added at entry points, and existing terminal signage was adjusted to direct passengers to the new walkways. The entry portals include bold gate-specific graphics to help assure travelers they are heading in the right direction toward gates B, C, D, E or beyond.

Because the corridor will be used for an extended period, significant attention was given to its branding, messaging and graphics. Fetters notes that designers enhanced the space with a “bit of surprise and delight.” In addition to using artwork to create a sense of place about San Francisco, they added vignettes of what’s in store for passengers after terminal renovations are completed. Encouraging messages include “Hey, you’re halfway there,” at the corridor’s midpoint and “Thanks for being flexible.” Fetters describes the overall result as playful brand identity.

Modular Approach

To simplify implementation, SFO chose a modular design with 11 prefabricated components. Construction of the modules started in February 2024 and took six months. Turner created a prefabrication yard at the airport but away from the terminal to reduce on-site operational disruptions.

Magnusson Klemencic Associates and Turner Construction collaborated closely with Fagioli, an Italian company specializing in self-propelled transport and lifting equipment, to ensure the modules were designed and fabricated to align with the company’s strategy for moving them to the terminal for installation. Over the course of 11 nights in September 2024, the massive modules were transported one per night across the airport using Fagioli’s self-propelled modular transporter. “It was very cool to see,” Katz recalls. “The longest module was longer than a 757 aircraft, and so to see that moving across the airfield and then getting set in place on bolt foundations within three-quarters of an inch of tolerance, was pretty amazing.”

Naturally, work on these connections could only begin after the modular units were on-site. As Turner Construction Company expected, the older building structures presented crews with extra challenges, such as differing site conditions and existing bypassing utilities. “In order to validate the existing conditions at the connection portals, we completed a full laser scan of both the interior and exterior of the existing and eliminated dozens of conflicts in advance of moving the corridors. However, there were still a handful of surprises,” remarks Michael Fahrenholz, Turner’s senior project manager. “The team was great and flexible in adjusting to handle those.”

Challenges and Solutions

From a design standpoint, the interim corridor project presented numerous challenges, such as positioning the prefabricated modules on the airfield without disrupting aircraft operations. This had to be accomplished while adhering to safety and code regulations, such as maintaining proper distances from fuel systems and pits, Katz notes. The team also had to balance the corridor’s width and location with the interior experience, ensuring optimal views and functionality. Gensler and the team successfully navigated these complexities to deliver a well-integrated solution, Katz says.

The eastern portion of the interim corridor includes a slight jog to accommodate the existing baggage system, which could not be relocated during the project. “I think, in some ways, it makes the corridor a little bit more interesting as you’re walking through it, because it isn’t just a long, long straight run,” Fetters comments. “There’s a turn.”

Lessons Learned

SFO emphasizes relationship-based contracting by using a progressive design-build delivery method, Katz notes. Project partners co-locate in a shared workspace known as “The Big Room” inside a repurposed landside hangar. The space accommodates about 200 team members, including contractors, designers, subcontractors, owners and project managers. “It enables everyday close coordination and collaboration so that innovative ideas such as these interim corridors…can evolve and be developed,” Katz explains. Although the interim corridor is a secondary component of the larger Terminal 3 West Modernization, it nonetheless received significant attention and resources from the project team.

This team approach has a significant impact on projects, adds Fetters. “A lot of it is culture-based—you set up the culture of understanding and expectations for these teams… I think that makes a big difference,” he says. “It’s not just a checkbox or a mandate on paper or contractual terms. It is everyone, holistically and culturally, prioritizing the project and what’s best for the project.”

Katz advises other airport leaders not to dismiss any idea as unrealistic—it might just be the right solution. In the case of the interim corridor project, prefabrication played a critical role in maintaining revenue-generating operations throughout construction, she adds. “There are huge benefits for ongoing operations of the airport,” Katz comments. “There are also cost efficiencies and safety efficiencies by doing that.”

Successful projects require clear objectives and decisive action, Fetters emphasizes. “It’s making big, audacious goals and decisions and then really following up on how to make it happen,” he explains. Modular construction, in particular, demands careful planning and early decision-making; changes late in the process will delay schedules and reduce efficiency. “You really have to commit and buy in,” Fetters cautions.

Another key takeaway from the interim corridor project is how effective modular design can be at minimizing disruptions during terminal construction. Palmer, from Magnusson Klemencic Associates, describes interim corridors as an excellent solution for maintaining a safe, enjoyable and stress-free passenger experience during construction in an active terminal. “By constructing the corridors offsite in modules, airfield disruptions were completely avoided, another essential when constructing at an active airport,” he adds.

Farenholz, from Turner Construction Company, commends the airport’s focus on providing a seamless, uninterrupted experience for travelers during construction. “SFO really is passenger first,” he comments. “Finding ways to keep the hundreds of thousands of people flowing really efficiently and unconfused is definitely what helps further innovation.”

Coming Up

Beyond the Terminal 3 West Modernization, SFO is undertaking several other improvement initiatives. The Terminal Main Hall Roof Project is addressing 25 years of wear and tear on the international terminal. The updates, executed on one-quarter of the facade at a time over two years, are designed to reduce leaks and improve the structure for ongoing maintenance. Scaffolding will wrap portions of the terminal façade as work progresses.

Another ongoing effort is the Shoreline Protection Program, designed to secure the airport’s eight miles of waterfront against sea level rise. Having completed the state permitting process required by the California Environmental Quality Act, SFO is moving on to the federal National Environmental Policy Act process. The project team hopes to begin construction sometime between 2025 and 2035.

Additional improvements are underway for the airport’s water treatment facility and electrical infrastructure.