Arup celebrates completion of C Concourse Expansion at SEA
Arup’s multidisciplinary design and engineering supported the delivery of a sustainability-forward design that enhances the passenger experience at Seattle-Tacoma International Airport.
Last updated: 11th June 2026
Arup joins the Miller Hull Partnership, Woods Bagot, and the Port of Seattle in celebrating the unveiling of the C Concourse Expansion (CCE) at Seattle-Tacoma International Airport (SEA).
A major milestone in the Port’s Upgrade SEA initiative, this transformative project is designed to improve passenger experience by enhancing circulation, comfort, and accessibility in the Pacific Northwest’s busiest airport. The project significantly enlarges the existing concourse, expanding it from 114,00 ft2 to 229,500ft2 and adding four new floors above the building. Targeting LEED Platinum certification, CCE will open to the public in June 2026.
As part of the Miller Hull team, Arup provided multidisciplinary engineering and design services to bring the upgraded terminal to life, from concept through construction. Arup’s scope included electrical engineering, airfield civil and logistics, façades, façade access and maintenance, and acoustics. The Arup team additionally designed a terminal-wide voice paging system that ensures clear, intelligible announcements for passengers.
“This project sets a new standard for sustainability at airports and for SEA, with many firsts including a dynamic folded façade and 500kW rooftop photovoltaic array,” said Jay Oleson, Project Director at Arup. “As a key partner to the architects and the Port, Arup brought multidisciplinary engineering to support creation of this ambitious design.”
Guided by the concept “Bringing In, Seeing Out,” the design restores a connection to flight and the surrounding landscape. A folded exterior façade responds to the concourse’s southwest exposure with patterning inspired by Northwest forests. Alternating south- and west-facing glass panels form vertical ribbons of light, each calibrated with dynamic tinting electrochromic glass to minimize glare and optimize daylight.
Inside, soaring volumes and framed sightlines draw passengers toward natural light and long views across the airfield. Designed to ease congestion, enhance comfort, and celebrate the region's natural beauty, the expansion prioritizes passenger flow, daylight, and sustainability.
Sustainability
As the first airport project to implement the Port’s Sustainable Evaluation Framework, CCE introduces several firsts for SEA, including its first photovoltaic panel installation, first all-electric project, first public outdoor space on the airside, and first project to target LEED Platinum certification. With Arup’s multidisciplinary engineering support for many of the project’s sustainable features, CCE establishes a new benchmark for future development at SEA including:
- All-electric, fossil fuel-free systems for heating and hot water
- 500kW photovoltaic array that will produce 12% of the project’s annual energy
- Electrochromic glazing
- Low-flow water fixtures
- Waste-reduction and food-donation infrastructure
- Biophilic design strategies
With its completion, the C Concourse Expansion represents a significant step forward in SEA’s ongoing transformation, demonstrating how thoughtful design, sustainability leadership, and collaboration can reshape the passenger experience.
“As the day progresses, the concourse responds to the changing light and weather of the Pacific Northwest,” said Rich Whealan, Principal at The Miller Hull Partnership. “On overcast, cloud-rich days, visibility is maximized to highlight the views of the airfield and Olympic Range, while soft, even daylight fills the interior, enhancing comfort and connecting travelers to the surrounding landscape.”
A light-filled space
At the heart of the expansion is a two‑story, daylight-filled marketplace inspired by Seattle’s public markets and civic gathering places. Dining and retail options surround an open, tiered seating area designed for live music and informal gatherings, while freestanding kiosks introduce variety and moments of discovery for frequent travelers. The Grand Stair anchors the space, connecting the concourse to mezzanine-level amenities and reinforcing strong visual and physical connections between levels.
Integrated into this central area is the Tree at C, a sculptural wood element that rises from the Grand Stair and branches into the wood ceiling above. Referencing the forests of the Pacific Northwest, it functions as both a point of orientation and a place to linger—supporting seating, integrated artwork, and framed views of the airfield. Natural materials grown and sourced in the Northwest are used throughout these elements, as well as in the terrazzo flooring below, emphasizing that this section of SEA is local not only in spirit but also in composition.
The Lookout at C marks SEA’s first public outdoor space on the airside, enclosed in glass and open to all passengers. From this elevated vantage point, travelers can enjoy unobstructed views of the airfield and the Olympic Mountains. Additional passenger-focused amenities include an interfaith prayer and meditation room, a nursing room, a sensory room, and a pet relief area, further supporting comfort, inclusivity, and choice throughout the journey.
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