EVERETT — The bluffs that offer panoramic views along Snohomish County’s coastline conceal a built-in danger.
The combination of steep slopes and the area’s torrential rains can cause soil, rocks and vegetation to sluice down hillsides.
Snohomish County’s coastal cities sit on land with a long history of geologic collapse.
“All the banks that surround Everett have been degrading since the last Ice Age and that will continue to happen,” said Kathleen Baxter, a spokeswoman for the city of Everett’s Public Works Department.
Mudslides can occur anytime the soil is saturated. The wettest October recorded at Paine Field — 7.52 inches of rain — has been followed by the fifth wettest November since record keeping began there in 1948.
These conditions have triggered recent National Weather Service warnings about the potential for slides.
One occurred Thanksgiving morning on Olympic View Drive in Edmonds, temporarily closing the road when mud slid onto the pavement.
Another occurred Nov. 28 on Marine Drive south of Stanwood, with the roadway limited to one lane as shoulder repairs continue through Dec. 28.
Mudslides occurred so frequently on the rail lines between Edmonds and Everett that they cancelled 206 train trips during the fall of 2012 and spring of 2013.
“Anywhere you have steep slopes, with the type of soils we have in the Puget Sound region, and with significant rainfall events, the soils lose their structures and are able to flow,” said Phil Williams, director of Edmonds’ public works and utilities.
Warning signs that a slide could occur include cracks in the soil where it’s beginning to pull apart, or wet and sinking soil at the top of a slope, he said.
Trees start leaning on a slope if it is moving even slowly, or the bottom 10 feet of the trunk will curve back into the slope as the tree tries to grow straight up, Williams said.
The potential for destruction can be enormous. The nation’s most deadly slide occurred in Oso in March 2014, killing 43 people.
Major slides in the Meadowdale area of Edmonds in the 1940s led to development of a rigorous review process for building in the area, said Leif Bjorback, a building official with the city of Edmonds.
Building on slopes and storm water management are some of the issues that are heavily regulated, he said. Geotechnical reports on building proposals must contain a statement that the development won’t increase the potential for landslide hazards.
A working group with representatives from Edmonds, Mukilteo, Everett, the state Department of Transportation, BNSF and Sound Transit meets every other month to talk about potential slide issues, said Janet Matkin, a state Department of Transportation spokeswoman.
When slides hit the tracks, passenger trains are halted for 48 hours to ensure safety.
Those slides have dropped significantly since a federal grant of $16.1 million paid for slide-prevention projects in six spots from Edmonds to Everett. The work, which was completed earlier this year, includes retaining walls to catch debris before it hits the tracks, slide-detection fences, slope stabilization and improved drainage systems.
The work seems to have been effective. Since July, there’s been six cancelled train trips, according to Sound Transit.
Three of the improvement projects took place in Mukilteo, where a big slide in 2014 hit the tracks, said Mayor Jennifer Gregerson.
“I think our community has a unique, appreciative, interest in storm water, hillsides and bluff property,” Gregerson said. Some building that took place in the 1940s and 1950s was developed “in a way that would not happen today,” she said.
The city now is considering approving low impact development standards. The goal is preserving native vegetation, better treatment of storm water, reducing impervious surfaces and releasing storm water off developed sites at a rate similar to what it would be if the site weren’t developed.
“The things that we do up the hill and upstream also impact the bluffs and the environment,” Gregerson said.
Next year, the city plans a study of improvements that could be made along bluff properties, she said.
“The reason that people like to live in Mukilteo is we have a beautiful environment, lots of trees and views of the water,” she said. “Our residents value that and understand we all play a part in keeping Puget Sound clean and preserving those aspects that make it such a great place to live.”
Sharon Salyer: 425-339-3486; salyer@heraldnet.com.
Slide warning signs
A hillside that has increased spring or seep activity, newly saturated ground, especially if it was previously dry.
New or developing cracks, mounds, or bulges in the ground.
Sagging or taut utility lines; leaning telephone poles, deformed fences, or tilting of trees on a hillside.
Sticking windows or doors; new or growing cracks in walls, ceilings, or foundations.
Broken or leaking utilities, such as water, septic, or sewer lines.
Separation of structures from their foundation; movement of soil away from foundations.
Changes in water well levels or water wells that suddenly run dry.
Movement of the ground.
Source: Washington State Department of Natural Resources
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