Risk of damaging mudslide was known, but given lower priority

OSO — Nearly 50 years have passed since that Saturday morning when the hillside above Oso crashed down and blocked the North Fork Stillaguamish River.

Bill Blake was just 8, but the Arlington man has vivid memories of that day, Jan. 7, 1967.

He accompanied his father, a PUD manager, up Highway 530 to check on Steelhead Haven, then a collection of vacation cabins on the river’s edge.

“I remember looking across at that big, gray rock hillside that came down,” he said.

Nearly four decades later, Blake was there in 2006 soon after the hill known as the Hazel slide let loose and again blocked the river.

Blake spent his working years at jobs with city and tribal governments in north Snohomish County. He’s one of many people here who not only knows the landslide’s history, but also the complex relationship between the river, the land and the people who call the area home.

Since the hillside fell again on March 22, killing at least 36 people and causing millions of dollars of property damage, much attention has focused on previously obscure documents. Among them: geological studies produced 15 years ago, a 2004 county flood-control plan that discussed buying out the neighborhood, and permits issued by the county to people who wanted to build near the hill that collapsed.

There were warnings that people and property were at risk. Why didn’t somebody do something earlier?

Some in the community say questions like that are inappropriate right now.

“People want to play the blame game and it ticks me off because we’re still in the recovery mode,” said John Koster, a former three-term Snohomish County councilman and state lawmaker who represented the Oso community for years.

Records are clear that federal, state, tribal and county leaders were aware of landslide risk at Oso, but they spent more of their energy and grant money on what at the time were the more pressing problems: the Stilly’s frequent flooding and the damage it does to fisheries.

There will be plenty of time for the county to take a closer look at what happened in Oso, County Council Chairman Dave Somers told council members last week.

“Looking back, the county clearly addressed the frequent, sure flooding event by doing buyouts of several communities,” Somers said. “And those are kinds of events that you can predict because they happen frequently. These other types of events are really not predictable — possible, but not predictable. We’ll have to have a policy discussion about those sorts of things.”

The county knows its coastline and mountain valleys feature numerous areas of landslide danger. An estimated 30,000 people live in those places, according to a 2010 natural hazard survey commissioned by the county. By 2035, the county expects to absorb roughly 200,000 more people. About 730,000 live here today.

The hills of glacial deposits at Hazel are inherently unstable. People have been recording slides there as far back as 1937, when aerial photographs documented the earth moving, according to documents compiled by the U.S. Army Corps of Engineers.

In addition to large slides in 1967 and 2006, parts of the hill also fell in 1942 and 1951.

Studies over the years document a clear connection between slide events and wet, rainy winters. This March was the second wettest on record, with nearly 15 inches of rain hitting Oso.

The 1967 slide brought down so much dirt that it moved the river channel 700 feet south and consumed three fishing cabins. There were no reported deaths or injuries. Corps records said the event provided a “spectacular example” of the hillside’s ability to move “sudden, fast, and over a large scale.”

“The whole mountain just slid into the river,” a local man, Joe Cooper, told The Herald at the time. “It just dried up the river.”

News coverage of the slide featured a trio of photographs from The Herald’s longtime spot news photographer Jim Leo. The captions quoted a state fish biologist, who opined that the slide would have no “appreciable effect on fishing in the stream.”

By 1999, fisheries concerns were paramount, particularly the destruction of salmon and steelhead spawning beds. The Corps studied the slide in conjunction with the Stillaguamish Tribe. By then, the hillside had been largely dormant for more than 30 years. Still, geologists warned that the river’s steady gnawing at the slide’s toe all but ensured the hillside would one day buckle. A study that year recommended diverting the river into a new channel at least 900 feet to the south. That was the greatest distance that geologists, back then, believed a slide from Hazel was likely to travel.

The March 22 slide crossed the entire valley, covering more than a mile.

In a 2000 draft study, the Corps identified five alternatives for addressing the slide, including letting nature take its course. That option wasn’t recommended, wrote Tracy Drury, an engineer and geomorphologist.

“Based on the available data, and assuming the future resembles the past, (the landslide) poses a significant risk to human lives and private property, since human development of the floodplain in this area has steadily increased since the 1967 event,” Drury wrote.

The study recommended acquiring private property to create a new river channel, well south of the hillside.

The draft report contained a list of property owners who would have to be persuaded to sell. A number of the people on that list now are among the dead and missing from the March 22 mudslide.

Over the years, some of the neighbors would have been leery of any government intrusion. In 2000, the Lavender Moon Society was listed as owning lot 8 at Steelhead Haven. The society was a “corporation sole,” a legal creation some property rights activists were using at the time to resist government regulation. The neighborhood later became home to Thom Satterlee, who died in the March 22 slide. He was best known for trying to create Freedom County, a place where state growth-management laws wouldn’t keep people from using their land as they saw fit.

The 2000 Corps report noted a low probability of finding willing sellers in Steelhead Haven. It estimated buyout costs ranging from $1.3 million to $2.2 million.

Meanwhile, the flooding Stilly in 1999 had torn up Chatham Acres, a similar community about four miles upstream. There, the river was carving a new channel and carried away one home. People who owned land there asked the county for help obtaining federal buyout money.

The county wanted to move people out of known floodways — the places in valleys where rivers put lives at risk by hopping their banks with destructive force. At Chatham Acres, the Stilly had carved a new 200-foot-wide, 800-foot-long channel through the neighborhood. Previous efforts to armor the riverbank and protect the homes had been unsuccessful.

The Federal Emergency Management Agency in 2002 agreed to pay 75 percent of the $1.9 million needed to buy out 10 homes and restore the 30 acres of riverfront at Chatham Acres.

The Chatham Acres buyout has received scrutiny since the March 22 slide. That’s because it was given a top-priority ranking in a 2004 county plan for coping with Stillaguamish River flooding. The same plan suggested the Steelhead Haven buyout, but gave it a lower priority.

The 2004 plan was developed by local, state, tribal and federal officials, as well as flood-district commissioners and farmers intimate with the river valley’s history. The focus wasn’t solely on human safety. It also sought to protect fish, wildlife and public infrastructure.

According to the plan, there was a “risk to life and property” at Steelhead Haven should another major slide occur. It also suggested people had seven to 10 years to shore up the hillside. Options included buying some homes on the opposite bank and creating “storage areas” that would provide enough space for debris from the hillside to safely run out, similar to what the Corps had suggested in 2000.

When the county’s flood management plan was approved in 2004, the Hazel hill had not seen a major slide for 37 years.

“It was one of the many identified problems, and there were other slides — Gold Basin, and Deer Creek was active at the time,” said Chuck Hazelton of Stanwood, a Stillaguamish Flood Control District commissioner who helped formulate the plan.

The plan also suggested that people living in the Stillaguamish River valley needed to know about the landslide risks. County emergency managers and stormwater specialists in 2010 asked that natural hazard maps, which showed landslide zones, be turned into interactive features on the county’s website.

“The greater accessibility of Natural Hazard data would facilitate the property owners’ better understanding of their vulnerability and lead to better planning, self-imposed mitigation activities, etc., which could reduce the need to respond during emergencies,” they said in an email pitch.

The request went to Brian Parry, an executive director for former County Executive Aaron Reardon, but it bore no fruit.

The 2006 slide created problems that the county, tribes and Steelhead Haven neighbors were wrestling with up until last month, records show.

When the hillside slid eight years ago, crews helped the river turn into a new channel, then shored up the bank to keep the water from devouring nearby homes. The work had impacts on fish, and the Stillaguamish Tribe obtained federal grant money to improve habitat.

The tribe for years has tried to stabilize the hillside. In January, the state signed off on a $600,000 salmon-recovery grant for the tribe to build logjams along the Stillaguamish, including at Steelhead Haven.

Meanwhile, county engineers worked on the riverbank at Steelhead Haven as recently as 2011. They restored the now-vacant Chatham Acres property to offset harm done to the river caused by managing the 2006 slide. Records about those efforts note that county crews had difficulty getting some landowners at Steelhead Haven to grant them access to the river.

Blake, who witnessed the aftermath of the 1967 and 2006 slides, now works as a planner for the city of Arlington. He co-chairs the Stillaguamish Watershed Council, a forum for farmers, environmentalists and governments focused on river management. He was involved in helping the county develop the 2004 Stillaguamish flood plan.

While the unstable slope above Steelhead Haven was a concern, nobody predicted the slide would bury the valley under a field of deadly debris, he said.

“It was definitely much larger than anticipated from any of the previous work or understanding from before,” Blake said.


  • Perimeter: 19,000 feet
  • Area: 245 acres (11,291,715 square feet)
  • Material displaced: 10 million cubic yards
  • Distance from northernmost point at the top of the scarp to farthest southern point: 5,827 ft.
  • Assessed value of structures: $3.4 million
  • Assessed value including land: $5.3 million


  • Includes slide and flooded areas.
  • Widest point: 9,826 feet
  • Perimeter: 35,154 feet
  • Area: 542 acres (24,6624,327 square feet, about 1 square mile)
  • Assessed value of structures: $5.4 million
  • Assessed value including land: $9.1 million


  • By slide: 115 properties valued at $5.85 million
  • By flood: 5 properties valued at $919, 300.
  • 36 single family homes valued at $4.8 million
  • 12 manufactured homes valued at $995,600

Noah Haglund: 425-339-3465, nhaglund@heraldnet.com.

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