OSO – A sudden slump in a rain-soaked hillside threatens to undermine Highway 530 and possibly cut off Darrington’s main access to I-5.
The road sank 6 inches along a 250-foot stretch Wednesday and Thursday midway between Arlington and Darrington, state Department of Transportation officials said.
If the slump leads to a major landslide, it would force Darrington drivers to take a 110-mile detour north to Highway 20 to reach I-5 in Burlington.
An average of 2,000 vehicles use Highway 530 each day, said Travis Phelps, a Transportation Department spokesman.
The fear of a big slide was underscored by the massive collapse two weeks ago of a hillside just a mile away that blocked and diverted the Stillaguamish River.
In both instances, extremely wet weather was the likely culprit, Phelps said.
“We’ve been having a lot of other problems around the state” because of the rain, Phelps said.
| In a slump
To check the status of slumping Highway 530 between Arlington and Darrington, go to the state Department of Transportation’s Web site, www.wsdot. wa.gov/traffic/weather/ updates. |
Due to the geology in the area, that part of Highway 530 is prone to slides, said Dave McCormick, assistant regional administrator for the Transportation Department.
The soil consists of sand mixed with clay, so when it gets waterlogged, the softer portions start to shift, he said.
Survey crews installed equipment at the new slump to determine if the hill is still moving, and if so, how fast, he said.
As a temporary fix, crews re-paved that section of highway on Thursday.
For now, the road should be safe to drive on, Phelps said. If it starts to slump more, the Transportation Department might have to close the highway temporarily to stabilize the hillside, he said.
“It depends how bad it is,” Phelps said.
The surveying equipment should provide enough information by Monday to determine how big a fix will be necessary, Phelps said.
Alternatives could include installing large drains to move more water out of the hill or building a large retaining wall, he said.
In Darrington, residents and business owners are monitoring the hillside closely.
“It will be a tremendous expense to the community to have that road closed, because there’s a lot of people up here that commute,” said Laurence Larsen, co-owner of Darrington Hardware.
Even if a closure only lasts a few weeks, businesses would feel the pinch of the 110-mile detour, he said.
“Definitely, the transportation of lumber and products” will be more expensive, Larsen said. “It’ll make Darrington less competitive in the market to get product to market.”
The site has long been known as a weak spot, Larsen said.
“I hope that the DOT can come up with a very quick repair that is cost-effective and lasts,” Larsen said.
Reporter Scott Morris: 425-339-3292 or smorris@heraldnet.com.
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