EVERETT — An emergency building moratorium drafted in the aftermath of the Oso landslide, if passed, would halt new home construction in almost all of Snohomish County.
And it’s probably not going to happen.
The County Council had been preparing to vote Monday on a temporary home-building ban within a half mile of known landslide areas. They’ve reconsidered, now that they’ve seen a map of what that would look like. County planners created the map for next week’s meeting.
The few areas in the county outside the half-mile landslide buffer are dominated by dangerously flood-prone river valleys, the new county map shows.
The largest buildable upland area of unincorporated Snohomish County is a stretch east of Marysville, between Lake Stevens and Arlington. There’s also a stalk of land west of Marysville, a patch along a three-mile stretch of Highway 9 in Clearview and some areas north of Stanwood.
Council Chairman Dave Somers first suggested the moratorium. He now acknowledges his original idea is unrealistic.
“Obviously, the half-mile mile buffer is overprotective and we will have to consider other alternatives,” Somers said in an email. “Common sense tells us that a vast majority of the areas within the buffers are not truly at risk.”
The March 22 slide left at least 41 people dead with two others missing and presumed dead.
The slide sent a hillside cascading across the North Fork Stillaguamish River valley, burying more than 40 homes in a matter of minutes.
Geologists for years had recognized that the hillside known as Hazel was unstable, but nobody is on record predicting a disaster of that magnitude. The same slope sloughed off and blocked the Stilly in 2006 and 1967, but caused no injuries.
County officials had in 2004 considered buying out some homes in Steelhead Haven, the same neighborhood where so many people would later lose their lives. They deemed a buyout there less urgent than other flood-proofing measures along the Stilly.
For more than a month, county leaders have fielded questions about what they knew about the slide history across the river from Steelhead Haven and why people ever were allowed to build homes there.
Somers pitched the moratorium on April 23 as a way to jumpstart a discussion about county policies that govern building near landslide zones.
Councilman Brian Sullivan asked for more time to study the idea. All five council members agreed. With the new map in hand, Sullivan’s glad they did.
“I was concerned,” he said. “The moratorium would have massive consequences.”
The county’s map does not include potential landslide areas in incorporated cities.
An early staff analysis of the County Council’s moratorium plan was way off the mark. It estimated fewer than 100 housing units could be put on hold. That was based on the county issuing an average of 1,200 residential building permits every six months.
A natural hazards plan prepared for the county in 2010 estimated that 30,000 people in Snohomish County already live in landslide zones, mostly along coastal bluffs and mountain valleys. That includes homes near slopes of greater than 33 percent and slopes of 10 feet or higher with certain soil characteristics.
Instead of imposing a full-scale moratorium, Sullivan supports temporary regulations that could be extended for six months at a time.
Those rules could include a varying scale for how far new homes need to be set back from geologically hazardous areas.
In his mind, more rigorous requirements for geotechnical studies also should apply, Sullivan said. He sent staff in search of appropriate rules that local governments have adopted elsewhere. They haven’t found anything yet.
The county needs to enlist scientists and engineers with landslide expertise to help craft its new rules, Somers said.
County planners are drawing up two additional maps showing smaller landslide buffers of one-quarter and one-eighth of a mile, county spokeswoman Rebecca Hover said. They’re also prepared to discuss alternatives to the buffers when the council meets Monday.
None of the homes at Steelhead Haven were in designated landslide-hazard areas under the county’s existing rules.
The closest home was about 400 feet from the toe of the slope. The county only requires a geotechnical study if a building site is within 200 feet of certain slopes, and that doesn’t necessarily prevent people from building. County code requires that buildings be at least 50 feet from the toe of a hazardous slope, or the height of the slope divided by two, whichever is greater.
A 1999 study for the Army Corps of Engineers, which some are citing as a warning county officials ignored, predicted a catastrophic landslide in Oso would stretch 880 feet.
The Oso slide extended for more than a mile.
“(I)f we use (a mile) as the standard for regulation, the entire county would be off limits,” Somers said. “Oso was clearly an extremely unusual and unexpected event in terms of magnitude and impact. There may not even be any other locations in the county were this type of event is even possible.”
Noah Haglund: 425-339-3465; nhaglund@heraldnet.com.
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