AMLI Arc Residential Tower / SeattleWA
What happens when Mortenson becomes more than just your builder?

The AMLI Arc is a 41-story, 393-unit luxury apartment tower in Seattle’s  Denny Triangle neighborhood, steps from Capitol Hill and downtown Seattle staples. The high-rise residential tower shares a 509-stall underground parking garage and ground-floor retail space with Tilt49, a 300,000 SF office building also constructed and developed by Mortenson. A continuous glass and metal facade wraps both towers, unifying the two developments while maintaining a distinguishable look. 

For the overall building design, architect and project partner ZGF prioritized wellness, social interaction, and connection to the outdoors. The project utilized rich colors and textures drawn from the Puget Sound environment, which were ultimately included throughout the informal lounge areas and landscaped outdoor spaces. The tower has amenities and public spaces on the 12th and 41st floors, providing tenants with breathtaking views of the Seattle skyline and – on a clear day – Mount Rainier, Puget Sound, Lake Union, and the Olympic Mountains. Resident amenities include a private party room with an outdoor dining area for intimate gatherings, a chef’s kitchen for hosting larger parties, an expansive fitness center and yoga studio, a media room, conference rooms, and co-working spaces. The large rooftop deck houses outdoor grilling areas, bicycle maintenance and storage areas, and a pet spa.

The apartments come in various floor plans ranging from studios to three-bedroom units featuring tall ceilings accentuated by floor-to-ceiling windows that fill the units with natural light. These options are further customizable with three aesthetic varieties, from units with exposed concrete ceilings and industrial-inspired interior design to luxury penthouses with condo-quality finishes. Select apartments also feature private patios or balconies to enjoy the expansive city views. 

During construction, activities required careful planning and coordination to keep streets and sidewalks open as much as possible and ensure the safety of everyone working on the five project sites spanning three square blocks. Mortenson’s team collaborated closely with the two neighboring contractor firms to ensure everything ran smoothly, from concrete placements and material deliveries to tower crane swing studies to understand how to safely share the air space. With the alley between AMLI Arc and the neighboring Kinects project just 18 feet wide, the deep excavations required to create their foundations threatened the stability of the soil between them. As a solution, ownership agreed to share the same trade partner to design the shoring systems and installation sequences to stabilize the alley. They successfully excavated the Kinects site and threaded rods extending from that shoring wall to the AMLI Arc, which Mortenson gradually tied into our shoring wall once excavation began.

Facts And Figures


429,000 Square Feet/393-Units

Completion: October 2017

Delivery Methods

General Contractor

The Team



DJC Building of the Year — Seattle Daily Journal of Commerce (DJC) 2017 Building of the Year