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Work on Portland International Airport‘s new $1.95 billion main terminal is moving to the sky. Four pieces of the massive, nine-acre timber roof are in place 鈥� with 16 still to go.

Moving each section is a feat that requires a self-propelled modular transporter capable of lifting a submarine. The entire roof will weigh about 18 million pounds.

The mega-structure will be supported by 34 giant Y-column stands. This summer crews were able to install 22 of the columns; the remaining ones will be placed in phases.

Each steel column is 55 feet tall and weighs 96,000 pounds. A special lattice boom crawler crane was used to lift them.

To ensure safety, no one was allowed underneath the columns when they were in the air. That included airport and Transportation Security Administration workers in the baggage center adjacent to the main terminal site. However, in an airport that can see 45,000 travelers daily such a restriction isn’t possible during daytime, leaving the wee hours of the night the only time available.

Once the last flight of the night was ready to take off 鈥� and all baggage center needs ceased 鈥� installation work could finally commence, said Katrina Day, a senior project manager with the project’s general contractor 鈥� Hoffman-Skanska Joint Venture.

Crews usually had a seven-hour window before flight activity resumed. During this time about 100 people 鈥� including spotters 鈥� worked on-site. Each time an area closed, a person had to stand there to make sure nobody entered the site.

During installation, each night the columns were transported 9.3 miles from Thompson Metal Fab in Vancouver, Washington, where they were fabricated, to the main terminal site. The columns were then rigged and tripped by the crane and lifted into place. Once each one was standing, a crew of about 24 people (including supervisors) manually cranked 48 2录-inch bolts 鈥� to secure it.

鈥淚t sounds very simple,鈥� Day said. 鈥�(But) it lasts all night.鈥�

By the end of the seven-hour window usually two columns could be installed. Some would take longer because they had to be threaded through the baggage center’s roof.

After the columns were set, isolators were placed atop each of the Y-column. The discs will allow the roof to move independently from the columns in an earthquake.

The main terminal construction site is at the heart of the airport. Crews have been working since 2020 to carve out the seat for the site. This included closing Clocktower Plaza, which housed pre-security shops and restaurants, and removing the 700-foot-long post-security hallway that linked Concourses A, B and C with Concourses D and E.

The structure was split in half and turned into two temporary hallways that bypass construction and connect the post-security hubs at each end of the airport to Concourses C and D. With the whole middle portion of the airport blocked off, all operations have shifted to the side. Kama Simonds, media affairs manager for the Port of Portland, said the big question is: 鈥淗ow do we keep the airport operating and get this project done?鈥�

Some practices already in place 鈥� like common use 鈥� help operational logistics. If an unscheduled flight needs to land at PDX early in the morning for some reason and a Y-column installation is under way, the aircraft could be directed to any of the common use gates (not leased to a specific airline) to not impede construction.

Such a practice allows the construction team to easily say, 鈥淐oncourse D is out of service; we’re doing a Y-column pick and setting it in place,鈥� Simonds said. 鈥淏ut over there at Concourse C, go to town.

鈥淲ithout that constant communication and close teamwork,鈥� she added, 鈥渋t would be a whole different ball game.鈥�

The situation for moving each roofing cassette is similar. Crews need about four nights to move, align, and slide each one into place over the terminal. All the work is done at night to not disrupt airport operations.

The process starts in the northeast corner of the airport’s property. Each cassette is raised off the ground 55 feet to column height by the modular transporter. Then the cassette is carried along the airfield at about 3 miles per hour to the main terminal site three-quarters of a mile away.

Installation of the whole roof is anticipated by the end of 2022.