Inside SR 520’s safety system in Montlake

Feb 22, 2024, 5:40 AM | Updated: 5:45 am

Wednesday was a great day. I had the chance to get on the new 520 Montlake Lid and check out some of the hidden features and safety systems.

The new three-acre lid is really taking shape. I was able to walk down what will become the new eastbound direct transit access ramp to the travel lanes. Workers were scurrying about doing all sorts of jobs.

I jumped down to the closed travel lane and back-tracked under the lid to a nondescript door in what appeared to be a solid section of concrete between the eastbound and westbound lanes.

More Chokepoints: Failing expansion joint continues to plague I-90 on Mercer Island

Inside I found the fire suppression valve room. This is a place that could save your life if there’s a fire inside the lid. The room is filled with massive pipes and 15 huge valves. Each one is responsible for a section of the 800 feet under the lid. Two giant foam tanks fill the middle of the space.

The Washington Department of Transportation’s (WSDOT) Steve Peer was my host. I asked him if someone has to press a button to start the system.

“No,” he answered. “It’s actually a heat sensor that senses heat and where it is and then it applies water and foam to that area so that we can put it out right away.”

The system will trigger as many valves as necessary to handle any size fire.

The foam is environmentally friendly, and the deluge system can be turned off remotely at the Traffic Management Center in Shoreline.

And while WSDOT is still perfecting the mixture of foam and water, it’s the lights inside the lid that are the reason for this weekend’s full closure of the freeway from 92nd on the east side to I-5. These news lights need to be calibrated for safety.

“What we want to do is make sure that the light outside matches the light inside,” Peer said. “To do that, we need to go through under the tunnel and calibrate how the light is at certain lumens for certain different times of the day. Essentially, if it’s a cloudy day, it’s it’s a lot darker. If it’s a sunny day, it’s probably its brightest.”

The tunnel lights, while necessary to light the darkness of the space, also need to match the actual light conditions. It’s so drivers aren’t blinded when they emerge into the sun or see black when they emerge at night.

More from Chris Sullivan: SDOT experiments with freight/transit lane

“For safety reasons, we want people going into what is essentially a tunnel at the exact same brightness,” Peer said.

This lighting calibration and the upcoming testing of other systems and features highlights that this part of the 520 Project is getting close to the finish line.

“We are in pre-commissioning mode right now, getting ready to make sure, like the lights this weekend, they’re ready to go when we open,” Peer said.

The lid project should be finished this summer. The new direct access ramp to the I-5 express lanes should open a little before that, but that ramp will start as transit only, eventually transitioning to HOV as well.

Both directions of 520 will close at 11 p.m. Friday. The lanes are scheduled to re-open by 5 a.m. Monday.

Check out more of Chris’ Chokepoints here. You can also follow Chris on X, formerly known as TwitterHead here to follow KIRO Newsradio Traffic’s profile on X.


Photo: A driver uses a phone while behind the wheel of a car on April 30, 2016 in New York City....

Micki Gamez

AAA: Washington is one of the worst states for distracted driving

April is Distracted Driving Awareness Month and to to shine a light on the subject, AAA Washington has teamed up with Safe Drive Club.

10 hours ago

Image: The Washington State Department of Transportation (WSDOT) closed part of Interstate 90 on Fr...

Steve Coogan

I-90 reopens after a closure due to an emergency tree removal

I-90 reopened after needing to close Friday afternoon due to an emergency tree removal, the Washington State of Transportation said Friday.

4 days ago

I-405 expansion...

Chris Sullivan

Sullivan: I-405 expansion to widen freeway in Bothell is underway

We've all seen I-405 expanding between Bellevue and Redmond, but construction to widen the freeway north of Bothell is now underway as well.

7 days ago

revive i-5 seattle...

Nate Connors

I-5 repair work to slow spring breakers, baseball fans this weekend

Beginning Friday night, three lanes of I-5 north between Albro Place and the West Seattle Bridge through Monday morning at 5 a.m.

10 days ago

Photo: April is Distracted Driving Awareness Month. Washington drivers can face higher insurance ra...

Nate Connors

Has your insurance gone up? Rates can take a hike for distracted drivers

April is Distracted Drivers Awareness Month. The President of NW Insurance Council says it has been working on prevention for years.

12 days ago

Signs in the eight light rail stations will provide real-time travel data for trains and destinatio...

Chris Sullivan

It’s not the whole enchilada, but light rail to roll on Eastside this month

Light rail service on the Eastside begins later this month. The eight stations are ready to roll. Test trains are running on the tracks.

12 days ago

Inside SR 520’s safety system in Montlake