New School On Washington Coast To Provide Tsunami Refuge
Up and down the West Coast, there are beach towns where it would be challenging to escape a tsunami.
That's because high ground is out of reach assuming the roads are buckled or jammed after a great earthquake. Now one low-lying Washington coastal town in that predicament is doing something about it.
Around this time next year, Ocosta Elementary School will have a new gym with a reinforced roof that can double as a tsunami refuge. This will be the first structure in North America purposely designed for tsunami vertical evacuation.
The school's students say the rare catastrophe weighs on their minds living, as they do, at the edge of the ocean.
"When I think of a tsunami, it kind of scares me,” sixth-grader Darcilynn Perrette said.
"I just think about it all the time,” fourth-grader Garett Jones added.
The students were at the groundbreaking ceremony Thursday. They pushed golden clam guns into the ground. Sixth-grader Kjirstin Hopfer joined alongside, as did various important grownups who wielded more practical shovels.
"It is exciting to have a new school here, and it's really cool to be the only school that is tsunami-safe,” Hopfer said.
A 1,000-person refuge
Westport, Washington is basically one long sand spit. The elementary and high schools were built on one of highest dune ridges around. But that's only about 25-28 feet above sea level, and that may not be high enough in the worst case scenario of a magnitude-9.0 full rip of the offshore Cascadia earthquake fault.
Models predict the subsequent tsunami will wash over pretty much everything for miles around. Structural engineer Cale Ash of Degenkolb Engineers in Seattle took that as a design challenge.
"The extra features would include the pile foundations, which were made a little bit larger in diameter and also deeper to make sure they could resist any scour, any washing away of the site that would happen from tsunami flow,” Ash said. ”The building is also designed to resist impact. As the water comes in, it can bring debris like logs and vehicles and other stuff."
Four outside stairways lead to a flat, concrete and steel reinforced roof capable of holding more than 1,000 people. Ash said the rooftop refuge is about 14 feet above the maximum estimated tsunami height. He said the design team relied on an estimate from the University of Washington, which predicted a tsunami surge could rise to 39 feet above sea level at that specific site.
School bond voters along the outer Washington coast agreed to tax themselves for the extra cost of $1 million to 1.5 million even though the area struggles with poverty and high unemployment.
"Our community... made the safety of children for this generation and generations to come its highest priority," Ocosta School District Superintendent Paula Akerlund said.
Major General Bret Daugherty from the Washington National Guard told the crowd assembled for the groundbreaking that the vertical evacuation structure should set an example.
"In the event of a Cascadia subduction zone earthquake, our entire coastline is at risk for tsunamis,” he said. “We really want to see this project succeed and then replicated up and down our coast, so we are keeping all of our kids safe and all of our communities as well.”
But Is It Tall Enough?
Fortunately, along most of the West Coast, natural high ground is not as far away as it is in Westport.
"Vertical evacuation to me is never the preferable option,” said Lori Dengler, an earthquake and tsunami expert at Humboldt State University. "If you talk to any emergency manager, they are not going to want to have people isolated on top of a building possibly for days — or maybe even a week or longer."
That said, Dengler understands sometimes the last choice is your only choice. In places like Westport and Ocean Shores, Washington and Seaside, Oregon, she said vertical evacuation could offer the only chance of survival and should be looked at.
Down the coast, two other low-lying communities are planning another kind of tsunami safe haven. In Long Beach, Washington and the Fairhaven neighborhood in Humboldt County, California, residents have proposed tall earthen mounds — a berm, artificial hill or "tsunami mountain.” The one about to enter the permitting phase in southwest Washington is being designed to hold more than 800 people on top. Like Westport, large parts of the Long Beach peninsula lack nearby high ground.
At one point, Cannon Beach, Oregon looked like it would have the first engineered tsunami refuge on the West Coast. But the idea to build a new city hall on stilts with an evacuation platform on top got way too expensive and was shelved in the last couple years.
Dengler said a key issue whenever such an evacuation structure is built is whether it's tall enough. After the devastating 2011 tsunami in Japan, the geology professor participated in a survey of the disaster zone that examined the performance of vertical evacuation.
The Japanese coast is the only place in the world where designated vertical evacuation structures are common. The reconnaissance team heard how this saved many lives, but also noted that more than 100 elevated safe havens were overtopped by the tsunami surges on March 11, 2011.
If the tsunami turns out to be a little bigger than expected, Dengler said people who evacuate inland to high ground "can continue to go up or inland." But she added, "Once you are on the third or fourth story of a four-story building, you can't go any higher."
The amount of time coastal residents and visitors have to evacuate to high ground varies depending on the distance between the earthquake epicenter and the coastline. Dengler says in her region - Humboldt County, California - the Cascadia fault zone is close to shore, leaving as little as 10 minutes to scramble to safety. Along the Washington coast, the interval between the end of the megaquake's shaking and the onset of massive waves could be 15-30 minutes.