Snohomish County officials were warned in a federally funded report in 2010 that neighborhoods along Steelhead Drive, nestled along the Stillaguamish River, were ranked as one of the highest risk areas for deadly and destructive landslides.
The report is the latest evidence that contradicts a Snohomish County emergency-management official who claimed the area “was considered very safe.”
The 2010 report — commissioned by the county itself to comply with a federal law — included a color map that highlighted dozens of areas in Snohomish County where steep slopes were most hazardous. A steep slope was defined as terrain that rose at a 33 percent or steeper grade.
The hillside along the North Fork of the Stillaguamish River, outside the small community of Oso, was one of those highlighted as most dangerous in the report completed by Tetra Tech, a California-based engineering and architecture firm.
“For someone to say that this plan did not warn that this was a risk is a falsity,” said Rob Flaner, Tetra Tech program manager and one of the report’s primary authors.
Flaner, who worked for 22 years at the Federal Emergency Management Agency, said the Steelhead Drive area was identified not only because of the steep slope but also because of a soil type that has been linked to landslides.
The 2010 study was only the latest in a series of geological surveys and technical reports dating to the 1950s that have spotlighted the risks of the hill along the North Fork of the Stillaguamish, about 16 miles from Arlington.
Snohomish County Executive John Lovick, who took office last year, said he was not familiar with the 2010 report.
There will be time later to examine the county’s building and landslide-safety policies, Lovick said. But for now, he said, county officials are focused on the massive rescue and recovery efforts in the slide zone, and on comforting the families of those killed or missing.
“We are going to look at this stuff. We’re trying not to second-guess anybody right now,” he said.
John Pennington, who heads Snohomish County’s Department of Emergency Management, said Monday that the hillside that collapsed had been considered “very safe” and that the slide “came out of nowhere.”
Asked about multiple reports contradicting that claim during a Tuesday news conference, Pennington said authorities had no way to predict Saturday’s disaster. “We did everything we could,” he told reporters in Arlington.
The 2010 report analyzed how many homes or buildings were at risk of damage from landslides in the county. Within incorporated areas, researchers determined, at least 467 buildings were at risk in Everett, the highest number, followed by 421 buildings in Mukilteo and 308 in Edmonds.
However, the county’s unincorporated areas encompassed more than half of all buildings at risk at 2,676 structures, the report concluded.
In all, landslides potentially threaten about $1.7 billion of real estate in the county.
Snohomish County is by no means alone in allowing development in areas prone to natural disasters like flooding and mudslides, said Tim Trohimovich, director of planning and law for Futurewise, an environmental group that has challenged developments in sensitive areas.
“I think unfortunately that local governments are allowing development in inappropriate locations,” Trohimovich said.
Whether Snohomish County could have moved homeowners out of harm’s way on Steelhead Drive is another question. “This is a tough case,” Trohimovich said.
Many of the lots wiped out in the slide near Oso had been there for decades — though county building records show several homes were completed after a major mudslide in January 2006, which did not destroy any houses but shifted the river closer to the homes along Steelhead Drive.
King County has tried to deal with a similar issue — houses built in flood-prone areas — by buying out homeowners.
Steve Bleifuhs, who manages the program for King County, said 225 properties have been acquired by the county since 1990, totaling 490 acres. In other instances, the program helps elevate buildings above flood level. The $65 million cost has been paid for with a mix of federal, state and local money.
A similar program could work for mudslide-prone areas, Bleifuhs said.
Snohomish County also operates a flood-zone buyout program for homeowners. Officials with the county did not respond to requests for information on the program.
The 2010 Tetra Tech report, “Natural Hazard Mitigation Plan Update,” was a follow-up to a 2005 study for the county. The 2010 report was presented to county officials, who conducted public meetings that were sparsely attended, Flaner said.
The report found that there was “little recorded information” about landslides in Snohomish County. But during the winter storm of 1996-97, about $35 million in damage occurred as the result of landslides, mudslides and debris flows.
As of 2010, landslides had not been linked to a single death in Snohomish County, the report found.
Landslides most frequently occur in January after the water table has risen during the wet months of November and December. Water is involved in nearly all cases, and “human influence has been identified in more than 80 percent of reported slides.”
The report analyzed risks and vulnerabilities from many kinds of natural events, including from a tsunami, flood and earthquake.
Reporter Brian M. Rosenthal contributed. Jim Brunner: 206-515-5628 or email@example.com. On Twitter @Jim—Brunner