Tuesday, April 28, 2015

A peek at the work happening inside the I-90 tunnels

By Mike Allende

Some of our work can be pretty high profile. You can readily see our crews paving lanes, filling in potholes, helping out stranded drivers or even building a new bridge.

Other times, it’s not as clear what’s going on when we have lanes closed. That’s kind of the case with the full weekend detours we’ve been doing on I-90 between Seattle and Bellevue. As you’re driving in the express lanes, you may not see much work happening on mainline I-90. That’s because most of the work is happening inside the Mount Baker and Mercer Island tunnels, and out of view of most drivers.

In order to add all-day carpool lanes on I-90 by squeezing in a fourth lane, contractor crews working for WSDOT and Sound Transit have to upgrade the tunnel’s fire detection systems, fire sprinklers and hydrants, cameras and other items that help to keep drivers safe in the event of fire or other incident inside the tunnels. While our maintenance crews do a great job keeping these systems in working order, it’s time to give things a bit of a facelift. The last time we made any big changes to the tunnel systems was about 25 years ago when I-90 was rebuilt. As the years go on it’s getting harder to get parts for these aging systems, not to mention the advances in technology that have happened since then. This project must be finished by mid-2017 to allow Sound Transit to begin constructing light rail across I-90.

In order to replace and install new cameras, lighting and fire suppression systems, we need bucket trucks and man lifts to reach the ceiling of the tunnels to drill and bore holes and install brackets for the equipment. We’re also doing pavement and drainage repair inside the tunnels. Over the next two years crews will:
  • Upgrade approximately 1,880 lights to help drivers and first responders see better inside the tunnels.
  • Install new, modern fire detection and carbon monoxide systems to provide faster and more accurate fire detection.
  • Replace 38 tunnel cameras to provide better information on incidents for our traffic management center and the public.
  • Improve the tunnel ventilation system with larger jet fans and vents to circulate clean air inside the tunnels.
  • Replace about 60 emergency telephones with new ones that include noise canceling and greater volume for use in reporting situations in a noisy tunnel.
Workers replace lights and other infrastructure inside the I-90
Mount Baker Tunnel.
Getting all of that new equipment manufactured, delivered, installed and tested is no easy task, and it takes time. By redirecting all traffic to the express lanes, crews can get more done in a shorter amount of time than they would with nighttime lane closures, and we can keep traffic moving without the visual distraction of crews working in the adjacent lanes. Doing this just with nighttime closures would significantly lengthen the amount of time needed to complete the project and impact the beginning of the light rail construction.

Detouring I-90 traffic away from the mainline allows major work to be
done without the visual distraction that could lead to traffic incidents.
After this weekend, there is one more full weekend directional detour of westbound I-90 on May 15-18. Contractor crews won’t need another weekend detour on I-90 until October. We appreciate everyone’s patience, feedback and flexibility while we get this work done.


Anonymous said...

Your instructions are silent on whether HOVs can get on the ramps in the International District as transit does regularly?

Anonymous said...

Is the term "man lift" a little sexist?

Anonymous said...

@Anonymous The term "man lift" refers to man. HUman. A person.. of either sex.

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