​Seattle's Massive SR-99 Tunnel Open to Public

BASF Helping Cities Improve Infrastructure for Tomorrow’s Needs

Seattle skyline along the Alaskan Way Viaduct

(Photo: Catherine Bassetti Photography)

This week the city of Seattle, WA is marking a momentous occasion, opening to traffic the massive SR-99 tunnel and highway through (and under) its downtown.

The SR-99 tunnel is a one-of-its-kind two-mile, double-decker, deep-bore tunnel that is replacing the old Alaskan Way Viaduct infrastructure.
The SR-99 project is a collaboration and investment of public and private sector, and is a mix of many projects for the benefit of residents and the successful growth of Seattle. Among the benefits of replacing the 1950’s viaduct infrastructure with the new tunnel and highway are: relieving congestion and improving traffic flow through downtown, increasing public access to the waterfront for enjoyment of the residents and improving access for commerce, and improving seismic resilience in the event of a substantial earthquake. 

One of the largest diameter tunnels in the world, the massive tunnel boring machine (TBM) “Bertha” broke through on the opposite end of the tunnel in 2017, excavating approximately 28 dump-truck loads of soil every 25 minutes during the height of its operation. After finishing construction on the tunnel's roadway, it officially opened this week. 

TBMs are typically named after a local celebrity, and Bertha, Seattle’s TBM is no exception. She was named after the city’s first woman mayor, Bertha Knight Landes, who was breaking ground in her own right by also being the first female mayor of a major American city, in the 1920’s.

Over the course of this project, BASF, through its Master Builders Solutions brand, contributed products, technologies, expertise and logistics, including:

Tunneling technology is one way BASF creates chemistry for a more sustainable future, helping cities improve infrastructure to prepare for tomorrow’s needs.