One month after a hillside collapsed burying dozens of homes and killing 43 victims, the work in Oso, Wash., remains a recovery mission, but plans are under way for rebuilding the stretch of highway devastated by the slide. The Washington Department of Transportation has been involved with recovering the victims, and will lead the efforts to establish State Route 530, the roadway linking the tiny town of Oso to the larger community of Darrington and beyond.
“There is a human aspect involved in this,” said Travis Phelps, WSDOT spokesman. “There were a lot of victims that lost their lives. Everyone is being very sensitive to that. We’re not just going in and bulldozing. We’re being very slow, thoughtful and meticulous. We’re using excavators, backhoes, hand digging tools and chain saws to go through this material very slowly, so if we encounter human remains we can get them to the medical examiner as quickly and in the best condition as possible.”
The mudslide occurred on the morning of March 22 in an area known as the Hazel slide, about 55 mi. (88.5 kg) northeast of Seattle. It traveled a little over a mile, coming down with enough force to go through a neighborhood, cross and dam the Stillaguamish River, cross the road and go up the slope on the south side, then came back down the south slope.
“It acted like a wave,” Phelps said. “It sloshed up one side and came back down. It’s a pretty big slide. We’re looking at big trees, pieces of houses, cars and some very, very soupy clay, sand/mud mix. This material is still very wet. When the slide came down it changed the whole geography of the valley. The U.S. Geological Survey estimated that 1 million cubic yards of soil were displaced. It was not a small slide by any comparison by any measure. It altered the course of the Stillaguamish River.”
In addition to looking for victims, workers also are taking care to find and preserve personal mementos, when possible, as well. But along with the challenge of the debris, the watery mud and enormity of the disaster, workers also must beware of contamination from gas cans, propane, septic systems and other toxins.
Once the recovery efforts are completed, the task will be to build a detour around the highway, and then to rebuild the highway itself.
The detour is expected to be about 2 mi. (3.2 km) and will travel over a Seattle City Light access road.
“Mobility is a big deal,” Phelps said. “The Corps of Engineers is making significant improvements to the access road. The National Guard made efforts to make it a more drivable road. We’re going to hire a contractor to maintain that road, open it up with limited hours as a one-way piloted detour for folks to get between Oso and Darrington. It will be for local residents only. You want to come and be a ’Looky Lou’ and see the landslide, this is not the road for you.”
Currently, it takes about an hour and a half to drive from Oso to Darrington — about 15 mi. (24 km) apart by Route 530. Before the slide, the highway was two lanes in each direction. It carried about 4,000 cars a day — 2,000 eastbound and 2,000 westbound. Most of the traffic were commuters, traveling between the rural Oso and larger Darrington.
“It’s very rural here and there is a big lumber mill as well with lots of logging trucks out here. With this highway out of commission it is a huge blow economically to the whole region, and very big blow to Darrington,” Phelps said.
When the work moves to rebuilding the highway, the first task will be removing about 100,000 cu. yd. (76,455 cu m) — or 10,000 dump trucks — of material from the highway. The debris covers about one mile of the highway and is at least 20 ft. (6 m) deep. But even once they do begin work on the highway, they will proceed much as they had while in recovery mode.
“There is concern of human remains on the roadway,” Phelps said. “A team of trained archeologists will be making sure we’re checking any material we are picking up, and looking at it when we are scooping it. When we are moving the materials, there will be another spotter there to watch the material when it comes out. There is just a lot of stuff here. All different types of materials. It can be easy on the initial move to miss something. So we want to make sure we have fail safe built in.”
Engineers won’t know what the condition of the highway is until they unbury it. Only then will they fully understand how much work there is to be done. And there are other considerations.
“There are a couple of big challenges,” Phelps said. “There are a bunch of small feeder streams. All have been altered and the path of the river has been altered. In addition to having soil conditions change, there’s lots of water here. What sort of culverts are we going to put in? This is also flood country. What highway replacement design … how do we have to change the highway given the Stillaguamish River is different now? The Stillaguamish River east of the slide is now about 11 feet higher now than it was before the slide. If you are an engineer, you need to know what is the water doing, what is the soil doing, what part of the road is still there? We don’t have that information yet.”
If the road is okay, WSDOT hopes to have one lane of State Route 530 open by fall. But if it’s badly damaged, it could take longer.
“We’re going to determine the scope of the work,” Phelps said. “We’re engaging families to see what their vision of the highway is. We need to get in there and do our homework, to say, here is what it will take to open it in current spot. Here is how we are going to deal with water, along with that will come a cost and timeline. Right now there are too many unknowns to say how much it is going to cost and when it is going to reopen.”
The state also plans to reach out to local contractors, and expects everything will be competitively bid.
“This is probably the biggest thing folks in the state of Washington have had to face since Mt. St. Helens erupted. It’s been the worst thing I’ve ever seen. You have to use your imagination because you can’t believe anything could do that damage.”