Interstate 5 is not earthquake safe, and there's no money to fix it.
Within our lifetime, there's a good chance Seattle will feel the violent tremors of an unimaginably strong earthquake—and when that happens, Seattle's stretch of I-5 will likely be damaged beyond repair.
The route that the busiest roadway in the state takes through Central Seattle involves a series of raised structures. Those structures include some bridges supported by hollow columns, which are now known to be especially dangerous in an earthquake. Lawmakers in Olympia have not allocated any funding to update those hollow columns, and there are currently no plans to do so.
Given these vulnerabilities, the state's earthquake response experts have completely written off trying to use I-5 in the event of a major seismic event. First responders will instead deliver lifesaving supplies on other roadways.
But I-5 is falling apart even if an earthquake doesn't strike soon. The roadway's pavement is 30 years overdue for replacement. By 2040, a whopping 278 of I-5's bridges in the region will be at least 70 years old and need to be replaced entirely. The latest government estimates put the cost of limping along with the I-5 we have (with minor fixes and patches) until 2040 at about $2.5 billion. And if you think I-5's traffic is bad right now, just wait a few decades when there are millions more people expecting to use it.
I-5 is facing these challenges just as voters across the state have actively defunded transportation projects, including basic bridge repairs, by passing Initiative 976, which cuts billions in transportation funding and limits car tab fees to $30.
The answer to what we're going to do about I-5 might come from the heart of Seattle, where urbanists in our region's largest city are looking for ways to mitigate the dangers this freeway poses. While lawmakers in Olympia avoid answering the question and statewide voters slash transportation funding, I set out to explore the radical ideas about the future taking shape. And what I found surprised me.
It turns out that building a multi-billion- dollar roof over I-5 with thousands of units of housing, restaurants, shops, art spaces, and open parkland on top might be an effective way of paying for making the freeway safe.
And then there's a second, even more radical idea. Since I-5 is an unsafe roadway that is failing in nearly every physical regard and there's no plan to fix it—and since freeways are helping to destroy the environment with tons of climate-causing pollution—there might be a solution staring us right in the face: It might be time to delete I-5.
Interstate 5 is Washington's most important roadway by nearly every metric. It's by far the busiest. According to traffic tallies from the Washington State Department of Transportation (WSDOT), 274,000 vehicles pass through Seattle's busiest stretch of I-5, north of Mercer Street, each day. (For reference, only 16,000 vehicles enter Seattle on Interstate 90 each day.) I-5 is the most important freight route in the state, and Seattle's stretch of I-5 carries the most freight weight. WSDOT estimates an average of 16,000 trucks carry goods through Seattle on I-5 every single day, moving more than 81 million tons of cargo annually in Seattle alone.
And nearly every way you look at it, our most important roadway is falling apart.
The roadway hasn't been seriously updated since construction started in 1958, after President Dwight D. Eisenhower signed the Federal Aid Highway Act. The five-star general's plan was to link all of the United States' major military installations together with one connected roadway that was free of tolls and traffic lights.
The federal government paid the majority of the bill, and work started with a double-decker bridge crossing the Ship Canal (the waterway that connects Lake Union to Lake Washington). The last section of I-5 in Seattle was finished in 1967 in South Seattle near Tukwila. Engineers expected the pavement to last 20 years, or till 1987, before it needed to be either heavily rehabbed or replaced entirely. That didn't happen. Most of the pavement drivers race over today is the same stuff that was on the ground in 1967, according to a report from the Puget Sound Regional Council (PSRC).
Pavement is only one of the many structural problems facing the roadway. Most of I-5's bridges, signals, railings, lights, drains, and barriers need to be either replaced or significantly rehabbed. That translates to $14 billion of work just to preserve the freeway statewide to 2040, or about $2.5 billion in the Puget Sound area, according to the PSRC report.
Bridges are one of the most worrisome aspects of these necessary repairs and replacements. An estimated $675 million needs to be spent on I-5's bridges to just keep them in working order until 2040, at which point, again, nearly every bridge on I-5 will need to be entirely replaced. And that $675 million includes only basic repair work; it does not represent the cost to make I-5's bridges seismically safe. It will cost an estimated extra $1.1 billion to retrofit the bridges for seismic safety.
That's a massive amount of money that lawmakers in Olympia have yet to fund. And given the fact that voters just slashed transportation funding, extra bridge money is unlikely to come anytime soon. This reality is why the state's emergency preparedness experts have decided to basically just give up on I-5 in Seattle.
John Himmel, WSDOT's safety and emergency operations manager, told me that in the event of a "catastrophic earthquake," federal supplies will first land at Moses Lake, east of the Cascade Mountains, and then be shipped to this area's airports, like Sea-Tac and Paine Field. The goods will then avoid I-5 in Seattle by using Interstate 405 and State Route 520's new floating bridge.
"Currently, I-5 is not going to be considered a lifeline because... some of the struggles of the major bridges in that corridor," Himmel said. "It goes around on 405 because it was a less expensive option to retrofit on 405 because of the money we had."
Most of the roads on this other "lifeline" are not even guaranteed to survive a really big earthquake. A Cascadia subduction zone (CSZ) earthquake, which would affect Seattle, would be the strongest type of earthquake. Only our region's newest engineering marvels, like the new Highway 99 tunnel and the State Route 520 floating bridge, are expected to survive a CSZ earthquake unscathed.
Road vulnerabilities are why the state estimates that in the event of a CSZ earthquake, you will likely be without help for weeks, not just days, according to Barbara LaBoe, a spokesperson for WSDOT. "We need the public to be aware that there is seismic risk in the region, and they need to be prepared for that," LaBoe told me. "People should have two weeks' worth of supplies. If there is a truly catastrophic earthquake, it may be a while before travel returns."
And there's no reason to think I-5's stretch in Seattle will be up and running quickly after a catastrophic earthquake. The 1950s engineering behind I-5 makes the highway prone to damage in earthquakes, especially along a smaller subset of bridges that are built out of columns that are entirely hollow on the inside.
There are 20 such hollow-column bridges across the state, according to WSDOT. Seven of those bridges (six on SR 520 and one along I-5 in Tacoma) are slated to be replaced, but there are no plans to replace or improve the remaining 13, all of which are on I-5. Six of these hollow-column bridges support I-5 and its on-ramps in Seattle between the convention center and the Ship Canal Bridge.
DeWayne Wilson, a bridge asset manager engineer at WSDOT, said it was "unfortunate" that this technology was used along I-5. He said it made the columns "a little bit more vulnerable" than if they were a solid core, but he also added that it's unlikely that these bridges would completely collapse in a major earthquake. He pointed out that these columns were not damaged during the 2001 Nisqually Earthquake, which had a magnitude of 6.8.
"Generally what we're saying is there would be some level of damage that would require [I-5] bridges to close, but it won't collapse. It just all depends on [the earthquake's] details," Wilson said. "Following an earthquake, the bridge would be closed and it might require repairs, but it would not collapse, that would be more of a rarity with our earthquakes."
Those hollow columns may have sufficed during the Nisqually quake, but what happens when we get a 9.0 CSZ earthquake? Wilson told KUOW in 2016 that there is a "high risk" that these columns could "implode" during a severe earthquake. John Stanton, a University of Washington engineering professor and expert on hollow columns, said in that same story that he would "stop talking and run" if he were standing underneath one of these bridges during an earthquake.
But Mark Gaines, a bridge and structures engineer at WSDOT, told me that new research by Stanton is showing that these bridges are actually stronger than was previously thought. "This concern about the implosion was a real concern, but through his testing it was not something that he has seen," Gaines said.
Stanton did not return a request for comment, and Gaines said the study he referenced could not be released until it is completed early next year. Gaines said it's unlikely that these I-5 bridges will totally collapse during a CSZ earthquake, but they might be damaged beyond repair. Gaines added that one unknown is how these bridges will handle an earthquake that shakes for a longer amount of time, which could happen with a CSZ quake.
"One thing we are looking at is how do our structures behave if they are in a high level of shaking for several minutes," Gaines said. "We don't have a lot of information around that."
Wilson reminded me that this wasn't a problem of physics or engineering. At its core, we are dealing with a political problem. If we spent enough money, we could get very close to guaranteeing that I-5 won't sandwich onto cars in the event of an earthquake and could function as a major safety route afterward. But that's ultimately up to voters and lawmakers.
"Everything comes with a cost, and we could label everything as essential, and it will be more expensive," Wilson said. "It's up to society to determine that. It's all about how much funding society is willing to put toward this need."
So if it's up to us Seattle voters to decide whether or not we want to rebuild our 50-year-old freeway, we can also decide to do something else altogether. Maybe it's time we just deleted it.
It's easy to feel like Interstate 5 is a natural part of Seattle. It cuts such a deep scar across the city that it's hard to imagine it not being there. But the freeway is not a natural formation, nor is it a particularly old man-made one (Pike Place Market, Smith Tower, and even the Space Needle predate I-5). So if the freeway is falling apart and won't serve us in an emergency, and if there's no plan to fix it, could we just get rid of it?
That's the revolutionary idea being pushed by Doug Trumm, a local writer and the publication director at the Urbanist. Trumm has been calling for the removal of I-5 from Central Seattle since 2016. He argues that given the roadway's deficiencies—it's falling apart, it's a huge driver of carbon emissions, it's nearly always gridlocked, and there's no money to update it—we should just scrap the downtown portion of the freeway entirely.
Trumm's idea has yet to win over any politicians.
"No, I haven't heard any support from people who hold office or senior posts, because they don't like to rock the boat like that," Trumm said. "But I certainly think there's an appetite for some ambitious things like this—which is better transportation, better parks, healthier cities, and less pollution."
Trumm argues that instead of rebuilding the old freeway, we should remove the roadway entirely between the I-90 and the SR 520 interchanges. That way, drivers would still be able to get near downtown, and east-west connections to our city's two floating bridges would still be intact. But the stretch of freeway between I-90 and SR 520—more than 50 blocks, worth more than a billion dollars, by Trumm's estimation—could be repurposed into housing, parks, and commercial development. Those are all things Seattle is in dire need of, while an unstable and aging freeway clogged with climate-destroying vehicles is something we might not need.
Trumm pointed to other freeway removal projects across the world, in places like San Francisco and Seoul, as proof that removing freeways can actually decrease congestion. He said his ideal version would set aside part of the current space I-5 takes up for an underground high-speed railway, although a spokesperson for WSDOT told me that it was unlikely I-5's right-of-way could handle high-speed rail, as the route curves too much for fast trains.
The biggest impediment to Trumm's plan is probably all of the freight that moves on this stretch of the freeway. Trumm said the Port of Seattle could still use I-90 for freight traveling east, and I-5 for freight traveling south, and the new Highway 99 tunnel (a $4 billion investment with no mass-transit benefits) for freight traveling north.
"I'm not going to say there are no impacts to freight, but I think they can still be mediated. And the idea that we can have less congestion may be appealing to freight companies," Trumm said.
The longer I talked with Trumm, the more it felt like we were armchair highway engineers in the war against cars. We were sitting in a coffee shop downtown that he had ridden his bike to and I had taken a bus and a train to. He told me he and his wife had donated their car to KUOW years ago, and now use only mass transit or bicycles. I own a car, but I drive it less than three times a month, and I try not to bring up my car ownership in polite company.
Trumm told me he didn't even want to expand I-405 to make up for removing sections of I-5. (He remarked: "The Eastside... already has enough freeways. It's not Seattle's problem.") But when I asked him if this idea was part of a war on cars, he had a quick retort.
"There's a war, but it's only picking up bodies on one side. It's a war on pedestrians, that's how we see it," Trumm said, invoking the broader "we" in solidarity with his car-free comrades. "As far as feelings go, they can feel attacked—and we don't intend that. The idea is that everybody has mobility choices, but what we have right now is that every street is going to have cars."
But it seems like there's no chance I-5 is going to not have cars on it in Central Seattle anytime soon.
I shared Trumm's freeway-deleting idea with Jeff Storrar, WSDOT's system-wide planning manager for I-5 and the person looking at how to coordinate the massive problems facing the freeway. The mild- mannered state employee gave me as strong a rejection as he seemed capable of.
"I would just reiterate... that we recognize that this is one of the most critical pieces of the transportation system in the state," Storrar said.
That isn't stopping Trumm from wanting to rip out the 50-year-old freeway. If suddenly Trumm was in charge of the world, he said he would move forward with his plan. "Yeah, when the eco-socialist-urbanists take over, I think we would do this," Trumm said.
When crews started the demolition of thousands of homes in the 1950s to make way for the new "Seattle Freeway," not everyone wanted a concrete scar to cut through the city. A movement to mitigate the damage of the incoming freeway started, and in the summer of 1961, marchers took to the streets. The protesters called for the roadway to be covered with a lid, urging the highway designers to "Keep Seattle Beautiful" by placing a park on top, according to a news report from the Seattle Times.
The protesters were able to delay the construction of the project for five months, according to a later story in the Times. But their reprieve from a freeway scar ended up being only temporary. Before the end of the decade, there was an unlidded concrete freeway stretching from Tacoma to Everett and straight through the heart of Seattle.
More than 50 years later, the calls for a lid over I-5 are being repeated, but this time there's an added urgency: Putting a cover on top of I-5 might be the best way to make our city's largest roadway earthquake safe.
The land below I-5 and the air above it are owned by WSDOT, the same agency that will likely pay for the necessary repairs to the road. If a structure was built above the freeway, WSDOT could sell or lease the land to private developers, and that money could then help offset the costs of repairing the roadway. It's the definition of a win-win: Seattle gets more land for housing, businesses, and community spaces, while the state gets money to fix its old road.
"Repairing the freeway is going to be expensive," Natalie Bicknell, one of the people advocating for lidding I-5, told me recently. "One of the reasons WSDOT likes our idea and is very supportive of it is because they need money."
Bicknell is part of the Lid I-5 coalition, a volunteer-driven group that is making significant progress toward reconnecting Seattle's downtown by building a new structure over the freeway. The lid has been endorsed by multiple members of the Seattle City Council, and was recently allocated $1.2 million to conduct a major feasibility study for lidding I-5 between Madison Street and Denny Way, approximately 18.5 acres of land. That study is due out in spring of next year.
The Lid I-5 group has already mounted a strong case for the project, even before the feasibility study is complete. An earlier study found that a lid over I-5 could support seven-story buildings across the entire structure, with some spaces able to support buildings as tall as 45 stories.
The ability to create new buildings along some of the most expensive real estate in the country makes the lid seem like a no-brainer investment in public land. The campaign estimates that it will cost less than $750 a square foot to build the lid, but the land created will then be worth more than $1,000 a square foot.
The lid's campaigners are officially nonpartisan on what exactly will sit on the structure—they want that to be decided by an inclusive outreach to various stakeholders—but they've worked with design students at the University of Washington to examine various scenarios. The cost of the lid and its economic impact vary significantly based on what kind of structures or parks are put on top.
One 2018 UW report, which studied a slightly larger area than the city's study area, found that a low-density design could net 1,842 units of housing (497 of those as affordable units) while still leaving 68 percent of the lid as open space, or 20 acres of new parks. That model would require $2.7 billion in total costs and net $2.1 billion in total value. But if the design had a higher density of buildings, with only 11 acres of parks and 4,531 housing units (1,223 of those as affordable units), then the project would require $4.4 billion in total costs but net $5.3 billion in total value.
The idea of putting 45-story buildings on top of I-5 in downtown Seattle might seem radical, but lidding freeways is nothing new. In fact, Seattle is home to what is probably the first lidded park in the country. Freeway Park opened in 1976 and is considered a national landmark for repurposing freeways. Riisa Conklin, the executive director of the Freeway Park Association, sees a lot of parallels between Seattle's new effort to lid I-5 and the effort that built this first freeway park.
"The momentum [behind Freeway Park] was grassroots and community driven, which is why I really love the Lid I-5 project as well, because it's coming from the community," Conklin told me as we walked around the winding Freeway Park recently. "It's a grassroots movement, volunteer driven, and it's again looking at how do we stitch this wound in our city and bring our neighborhoods back together? How do we create more public land, more public housing—the things that our city needs most."
Cities around the country—including Dallas, New York, Chicago, and Washington, DC— have followed the example of Freeway Park and designed and built lids.
Even the Seattle area has a growing list of lidded parks. Interstate 90 passes under two lids as it leaves Seattle, first at Judkins Park and then on Mercer Island, where the interstate is buried under one of the largest lids by square footage in the country. Medina is home to two lidded parks over SR 520. Bellevue is in the process of building a lidded park over I-405. And WSDOT will begin construction of a new lidded park over SR 520 on north Capitol Hill near Roanoke Street in 2023.
There's a pattern among these Seattle-area lids: They're near the homes of rich people. So it only makes sense to build one in the heart of downtown, where median incomes are lower than ultra-rich areas like Mercer Island, especially since this lid could create badly needed affordable housing.
The Lid I-5 group wants to finish construction of I-5's downtown lid within 10 years, a plan they think is reasonable.
"Every time WSDOT builds or repairs a freeway, they put a lid on it," Bicknell said. "We know it's going to happen. We just don't know when it's going to happen. Our group doesn't want it to happen in 50 years."
Besides, who knows if I-5 will still be standing in 50 years. The last megathrust earthquake from the Cascadia subduction zone was more than 300 years ago, and seismologists estimate those quakes happen at regular intervals every 400 to 600 years. That means it could strike tomorrow, or it could hit in hundreds of years. Either way, the I-5 of today isn't ready for it.
"We feel like Seattle should be able to do this. It's so much wealthier than many of the other cities that are doing this, and it has a greater need," Bicknell said.
"And let me tell you this—none of those places have the seismic concerns that we have," she said. "All of those places simply did it to improve their urban environment. Making the modifications to I-5 that are necessary to make it safe would save lives in the event of an earthquake. What could be a better motivating factor than that?"