Downtown Seattle Transit Tunnel Mechanical Studies & Engineering


Sound Transit


Seattle, WA






Civic & Public

Project Team
Mike Lehner
Associate, Senior Project Manager
Nick Baker
Principal—Mechanical and Commissioning
Matthew Woo
Associate, Electrical Engineering
Melissa Evans
Project Assistant
Andy Brown
Associate, Vice President
Supporting Seattle's Underground Transit System

We provided mechanical and life safety system subject-matter expertise to support evaluations and upgrades in the tunnelways, stations, and associated areas of the 1.3-miles long Downtown Seattle Transit Tunnel (DSTT). This five-year task-order contract was part of preparations for the transition of tunnel ownership to Sound Transit in 2022.

We supported life safety and egress systems evaluations and tunnel exhaust assessments. We also helped develop the safety and reliability review report and a site safety plan template, including COVID-19 safety protocols, both used throughout the duration of the contract.

From 2009 to 2019, the DSTT was North America's only transit tunnel that includes stations and service for both trains and busses. The 30+ year old tunnel continues to serve Sound Transit's expanding Link light rail system.