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The fire-suppression system in the I-70 tunnels is a critical Colorado insurance policy. We toured it to find out why.

The Colorado Sun spoke to the experts who run the tunnels to learn more about their fire suppression system and how they work. Here’s what we found.

The Eisenhower-Johnson Memorial Tunnels. (Jesse Paul, The Colorado Sun)
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BENEATH THE CONTINENTAL DIVIDE — If the Eisenhower-Johnson Memorial Tunnels are Colorado’s high country artery, think of its $20 million fire suppression system as the health insurance policy that keeps it pumping.

At the very least, the system is meant to prevent travelers from experiencing something truly heart-stopping, like the 1982 Caldecott Tunnel fire in California that left seven people dead. But more realistically, it’s a way to make sure that traffic keeps flowing along Interstate 70 in the event of a much more likely, and less tragic, vehicle fire.

Completed in 2015, the system reflects the Colorado Department of Transportation’s increased focus on the importance of the pair tunnels that carry growing numbers of people and goods to and from the Western Slope each year. 

“The system is a risk mitigation strategy,” said Stephen Harelson, chief engineer at the Colorado Department of Transportation. “The goal is to preserve human life first, protect the tunnel from long-term damage second.”

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There are typically one or two fires in the tunnels a year. A fire that gets out of control could shut down the highway for hours. 

Each hour the tunnel is closed there is an estimated economic loss of up to $800,000 per hour from travelers and $1.8 million from freight, so it’s easy to understand the math of the suppression system’s importance. That’s not to mention the fact that drilling a new tunnel could cost north of $1 billion. Construction on the existing tunnels was completed between 1967 and 1979 at a cost of about $262 million.

“It only takes a few fires for you to get your return on investment,” said Neal Retzer, CDOT’s tunnel resident engineer in charge of overseeing the route. 

Here is what else The Colorado Sun learned about the fire suppression system during a tour:

Vehicles pass through the Eisenhower-Johnson Memorial Tunnels on Monday, Oct. 7, 2019. (Jesse Paul, The Colorado Sun)

Fiber optics, cameras and trial and error

The fire suppression system is, for the most part, something that the traveling public will never know is there. It’s made up of hundreds of nozzles hanging from the tunnels’ ceilings, a web of pipes and pumps and a public-swimming-pool-size tank of mountain stream water ready to be put to use at any moment.

Each nozzle has the ability to drop 500 gallons of water per minute and the reservoir of water it draws from has a capacity of 120,000 gallons.

Neal Retzer, CDOT’s, tunnel resident engineer, shows off part of the Eisenhower-Johnson Memorial Tunnels’ fire suppression system. (Jesse Paul, The Colorado Sun)

The system can be triggered manually or through a series of fiber optic sensors that alert tunnel operators when the ambient temperature in the tubes increases by 25 degrees or more. 

“The cameras will turn to that hot spot and a little alarm will go off and let you know ‘Hey, something’s going on. Take a peek at it,’” Retzer said.

But typically the 24/7 staff monitoring the tunnels’ from an impressive array of live-camera feeds can see a fire situation before the sensors even notice that there is trouble. The suppression system was manually launched to slow two recent fires — one in January during a blizzard and  one in September, when a box truck loaded with cardboard caught fire.

(Those are the only two times the suppression system has been used since it was installed, and officials say it worked as it was supposed to.)

Workers in the Eisenhower-Johnson Memorial Tunnels’ control room. (Jesse Paul, The Colorado Sun)

“Most of them, we see (vehicles are on fire) before they even come to a stop,” Retzer said.

Tunnel operators can pinpoint where a fire is and start sending water shooting out of the ceiling onto the exact area from a computer system, sometimes using a little trial and error to get the spot down pat. 

Any water that is used as part of fighting a fire is captured and treated before it is released back into the surrounding watersheds. 

Is it really necessary?

Bryan Trigg, who works in the operations center and also doubles as a firefighter, was one of the first on scene during the January car fire in the eastbound tunnel. 

“It was scary. It was pretty intense,” he said. “You get in there, you just see a wall of smoke.”

He said the fire suppression system was going and was like a “tropical downpour” coming down in freezing temperatures. But, he adds, “I never did feel like I was in danger of anything other than freezing.”

Before the suppression system was put in place, CDOT’s response to a fire in the tunnels was pretty basic: turn on a giant fan system to force smoke out one way or the other and send in firefighters on a truck built in the 80s to try and put it out. 

“Our big pumper truck is from 1986,” Retzer said. “That old girl needs a lot of love just to keep it going.”

Step inside the orange truck and the cab smells like vinyl — “that’s what a new car from the 80s smelled like,” Retzer jokes. CDOT also has a converted pickup truck stationed at the tunnels to fight fires, similar to ones used by crews fighting wildfires.

CDOT’s Eisenhower-Johnson Memorial Tunnels fire truck. It was made in 1986. “That old girl needs a lot of love just to keep it going,” said Neal Retzer, CDOT’s tunnel resident engineer. (Jesse Paul, The Colorado Sun)

It takes about 10 to 12 minutes for firefighters from Georgetown or Silverthorne to make their way to the tunnels if they are needed.

The number of fires in the tunnels have actually decreased in the past three decades even as the number of vehicles passing through them has gone up, now at more than 32,000 each day. In the 80s, there was an average of one fire in the tubes each month, many of them campers.

The suppression system is meant to keep a fire from getting out of control, not extinguish it. 

“It keeps it knocked down and it keeps it cool,” Retzer says. “It preserves the structure and then the pros show up to put it out.”

And just that help can make a world of difference, CDOT says. The box-truck fire in September was knocked down by the suppression system before flames could spread to its cargo of cardboard. 

“If it got to the back, I mean we might still be working on the tunnel right now trying to reopen it,” Retzer said. “That would have been so hot.”

Neal Retzer, CDOT’s, tunnel resident engineer, hold a photo of a camper fire from 2000 in the Eisenhower-Johnson Memorial Tunnels. (Jesse Paul, The Colorado Sun)

What about hazmat vehicles?

The Colorado legislature this year ordered CDOT to study whether and how the suppression system could be upgraded to allow hazardous materials vehicles to pass through the tunnels. 

Right now, those tractor trailers make the treacherous trip over Loveland Pass, a route that’s difficult to navigate on a sunny day, let alone during a blizzard.

MORE: Hazmat tankers want off “sketchy” Loveland Pass and into tunnels. Years of debate could be decided once and for all.

It’s not clear that there will be a solution. The system right now is set to keep a 20-megawatt fire in check — roughly the energy generated by a burning car or motorhome. A hazardous-materials fire, by comparison, has the potential of generating 200 or 300 megawatts of energy.

“There is no roadway tunnel in the world that contains a fire suppression system that would extinguish a 200 megawatt fire,” said Harelson, CDOT’s chief engineer. 

Even if there were systems made to work in other tunnels elsewhere, the Eisenhower-Johnson Memorial Tunnels present different challenges. They are at an elevation just over 11,000 feet and are among the longest in North America at 1.7 miles each.

The Eisenhower-Johnson Memorial Tunnels. (Jesse Paul, The Colorado Sun)

Also, hazardous materials trucks don’t always carry flammable substances. 

“There’s a lot of different hazmats,” Retzer said. “If you had liquid nitrogen going through there, that tank tips over and breaks open, that’s not a fire. All of that liquid turning into gas is just going to put all the air out. You’ve got a much different problem.”


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