The roads are installed – now it’s time to finish the tunnel’s smart systems
A double-deck highway now runs end to end inside the new SR 99 tunnel. Earlier this month, contractor Seattle Tunnel Partners (STP) installed the last of the 1,152 road panels that together form the lower (northbound) roadway.
Now crews are installing and testing the tunnel’s operational and safety systems. It’s a big job. Inside the tunnel there are:
- More than 300 cameras to monitor traffic and security at all times as part of an incident-detection system.
- Automatic ventilation systems designed to keep air quality and visibility high.
- Automated sprinkler systems designed to put out a fire quickly at its source.
Together, these systems will make the SR 99 tunnel one of the "smartest" tunnels ever built. This video explains how the critical air quality and fire safety systems work together:
Thousands of components that make up the safety and operational systems will be tested at least three times – once to make sure they work, then to make sure they work as a system, then together with other systems to make sure all systems are integrated and functional. After the systems are all certified, STP will hand the tunnel over to the Washington State Department of Transportation so a different contractor can realign SR 99 and build the final ramp connections to and from the tunnel.
By the miles:
The SR 99 tunnel has approximately:
- 95 miles of electrical wiring
- 21 miles of sprinkler pipes
- 15 miles of lights
- 13 miles of fiber optic cables
- 8 miles of linear heat detectors