May 11, 2020

Port readies $340M expansion of Sea-Tac Airport's C1 Building

Image from Port of Seattle [enlarge]

Four levels and a mechanical penthouse will be added to the C1 Building. It’s the only substantial area at Sea-Tac where the port can build upward instead of outward.

The Port of Seattle has issued a final determination of non-significance for a $340 million addition to Sea-Tac Airport's C1 Building, where concourses C and D meet.

Plans include a four-story addition of 104,000 square feet to the existing 99,000-square-foot building, which is two stories with a basement. Renovations will be made to the existing baggage (below grade), bridge (at grade) and concourse (above grade) levels. New dining and retail spaces will be added at the concourse level along with new seating and a 1,300-square-foot expansion of the adjacent Gate C3 waiting area. There also will be a new mechanical penthouse, as well as a loading dock with trash compactors.

About 40,000 square feet will be reserved as office and lounge space in new and existing levels, including 7,000 square feet for lounge operators on the new levels.

An agenda for a March 10 port commission briefing said the port is in preliminary negotiations with several tenants interested in the lounge space. It said there is pent-up demand for premium lounges at the airport.

Other elements of the project include a post-security meditation room, a room for nursing mothers and new restrooms.

The agenda said the C1 Building is the only substantial area at Sea-Tac where the port can build upward instead of outward.

Existing baggage operations, at the baggage and bridge levels in C1, will be replaced by a centralized baggage system that is being built in three phases. PCL Construction Services last month finished the first phase, which is below the central terminal. Phase two improves baggage systems to the north and phase three improves systems to the south.

New offices and storage will be built on C1's baggage and bridge levels, with space for Transportation Security Administration's central monitoring operations.

The existing concourse level will get additional concession space and a new mezzanine level will add to the dining and retail mix. Levels 1-3 above will have offices and lounge space. A long skylight will channel light into a five-story atrium.

The agenda says the exterior of the addition will likely be a combination of metal panels and glazed curtain wall similar to that found on other airport buildings.

Two early hard construction cost estimates have been made: $189.2 million and $207.1 million. The port says these preliminary estimates could vary by 15%-30% on the low side and 20%-50% on the high side because designs are at a very early stage.

The project is scheduled to go before the port commission on May 26 for final authorization. If approved, a bid advertisement for a designer and general contractor/construction manager would follow at a to-be-determined date. The port said it wants the contractor involved with the early design process to help keep costs down.

The C1 expansion is the first tier-three project under the port's new Sustainable Project Framework, which requires designers to conduct sustainability and cost analyses. This includes options to reduce energy and water use, and provide technical specifications and amounts of concrete, steel and gypsum in an effort to reduce carbon emissions.

The port has an aspirational goal of using woman- and minority-owned businesses as 9%-15% of the design team and 8%-15% of the construction team. It said final goals will be set before bids are advertised.

Aecom has done early design work.

Port documents indicate designs will be finalized in the second quarter of 2022 and construction will kick off with demolition in the following quarter. Construction will take five years.

The final DNS can be appealed until May 22 to King County Superior Court.

The C1 Building was built in 2005 as the airport's baggage screening facility, with some office space. It was designed to expand to six above-grade levels.

The port said the airport is not meeting current demand for food, beverage and retail options, especially on concourses C and D. Expanding those services in the C1 Building is expected to help alleviate that and provide more choices for travelers.

For now, crowding is not a problem due to the COVID-19 pandemic, as daily departing passengers have dropped to 2,500-3,000 compared with a typical day of 50,000 at this time of year. A port spokesman said it could be two years before operations get back to normal, but at this point it's anyone's guess. He said it may not get back to normal until a vaccine is developed for the coronavirus.