EVERETT — The Snohomish County Council has prepared an emergency moratorium to prohibit building within a half-mile of landslide hazard areas, such as the hillside near Oso that collapsed March 22.
The proposed legislation would have a huge impact along coastal bluffs and mountain valleys, where an estimated 30,000 people already live in parts of the county with known landslide dangers.
“It would be a six-month moratorium, which is all we can do by ordinance,” Council Chairman Dave Somers said. “It would prohibit any new construction, any new housing construction, within a half-mile of a landslide hazard zone throughout the entire county.”
The ordinance is expected to be introduced at the council’s regular 9 a.m. Wednesday meeting. It would not apply to projects with completed building applications.
The zones subject to the moratorium would be defined by the county’s rules for building in critical areas and a 2010 study of natural hazards.
The county’s critical areas rules, last updated in 2007, require a special review for building sites within 200 feet of a known landslide area.
The mudslide that hit the rural Steelhead Haven neighborhood east of Oso stretched 5,827 feet — more than a mile — from the scarp to the farthest southern point. It covered 245 acres in an estimated 10 million cubic yards of debris.
The county’s existing 200-foot buffer for geologically hazardous areas would not have applied to any of the homes destroyed by the March 22 slide, which caused 41 confirmed deaths with two more people listed as missing.
The closest of the more than 40 homes destroyed that day was well over 300 feet from the toe of the slope.
Two big slides on the same slope blocked the North Fork Stillaguamish River in 2006 and 1967.
Given a history of instability, geologists, as early as 1999, had warned that the slope was at risk of failing again. However, they did not predict that debris field would extend more than a mile, clear to the south side of the valley.
For county policy makers, the overriding safety concern in recent years was always flooding. In particular, they worried about the river endangering lives and property when it carved out new channels.
In 2002, the county secured a Federal Emergency Management Agency grant for a $1.9 million buyout of 10 homes a few miles upriver from Steelhead Haven. Those homes were considered in imminent danger.
A 2004 plan to address flooding on the Stilly considered buying out homes at Steelhead Haven, but gave it a lower priority than competing projects. Officials believed they would be able to manage risks by shoring up the hillside to the north. At the time, they mainly had an eye toward managing flood dangers and protecting salmon and steelhead fisheries.
A lobbyist for the area’s largest homebuilders group agreed with the county’s decision to prioritize safety through the moratorium.
“The impact on the building industry would be extremely minimal in the short term,” said Mike Pattison of the Master Builders Association of King and Snohomish Counties. “We have to be mindful of the fact that these landslide areas are largely rural areas and the vast majority of construction happens in urban areas. While there may be a development or two affected, the big picture is that it will have a minimal short-term impact on development.”
Somers said he hopes the emergency moratorium will give the county a chance to assess its building codes and how it can better gauge risks, perhaps through newer technologies such as LIDAR, which can be used to map landscapes from the air.
There’s also a question about where to draw the line when it comes to regulating safety.
“In general, there’s a question about the county’s role in prohibiting development,” Somers said.
If the council passes an emergency moratorium, it must follow up with a public hearing within 60 days.
Noah Haglund: 425-339-3465, firstname.lastname@example.org.