State Route 99 tunnel main


In Seattle, HNTB used Tekla BIMsight for the State Route 99 tunnel project by easily combining models from all disciplines, reviewing those models with smooth navigation features and capturing areas of interest with ease.

Seattle's massive tunnel makes travel safer – with Tekla BIMsight


The Seattle Tunnel Partners design-build contractor team hired HNTB as the designer for the State Route 99 Tunnel project which will replace the Alaskan Way Viaduct section of State Route 99 along Seattle’s waterfront with a 16-meter inside diameter bored tunnel beneath downtown Seattle. The existing Alaskan Way Viaduct section is an elevated roadway that is at risk of failure from earthquakes. As a member of the Seattle Tunnel Partners, HNTB is providing the design services for the tunnel and the two associated operations buildings. Initial construction activities began in fall 2011.

Cut and combine models

Tekla BIMsight allowed HNTB to easily combine models from all disciplines and view models with smooth navigation features and capture areas of interest with ease. In BIM collaboration, HNTB utilized the model in weekly all-discipline coordination meetings to discuss the two buildings, cut and cover areas, and the tunnel with the sub-consultants, architects, and engineers. With all of the discipline models loaded into Tekla BIMsight, HNTB and project participants were able to see conflicts and possible design changes.

In this project, the Tekla BIMsight feature HNTB found most useful was the ability to quickly cut sections and turn off pieces of the model to clearly see the interworking of the design within the model. 

BIM over drawings

State Route 99 Tunnel is an extremely complex project which combines civil engineering, structures, architectural elements, mechanical & electrical systems, and traffic management. When the workflow is model-based, the design team can view the integrated project elements as a whole and find design and coordination issues between each discipline. The traditional method of reviewing the project using drawings does not allow for this complex interface and collaboration process.

HNTB sees that the industry is leaning more and more towards 3D model-based design. Showcasing some of their previous projects within Tekla BIMsight will encourage the continuation of projects to be created in 3D verses the traditional 2D plan work.

HNTB at a glance

The US-based HNTB Corporation is an employee-owned infrastructure firm serving federal, state, municipal, and private clients. Professionals provide award-winning planning, design, program management and construction management services.

For nearly a century, HNTB has helped create infrastructure that best meets the unique demands of its environment. With client relationships spanning decades, HNTB understands infrastructure life cycles and has the perspective to solve technical challenges with clarity and imagination. The company sees and helps to address far-reaching issues of financing, legislation, design, construction, community outreach and ongoing operations. As employee-owners committed to the highest levels of performance, HNTB enables clients to achieve their goals and inspiring visions.

In BIM collaboration, we utilized the models in weekly all-discipline coordination meetings. With all of the discipline models loaded into Tekla BIMsight, we were able to see conflicts and possible design changes.

State Route 99 Tunnel
Jason Seck
BIM Consultant