This story was originally published on LincolnChronicle.org and is used with permission.
The sheer magnitude of a landslide that blocked a quarter-mile section of Oregon 229 north of Siletz has left state highway officials unsure when the debris will ever be cleared.
“Months? Years? Or longer?,” Mindy McCartt, an Oregon Transportation Department spokeswoman told Lincoln Chronicle. “We have no idea of just how much material has come down off that hillside and it could be quite some time before we can even get in there to accurately assess it.”
The massive slide Dec. 12 was likely triggered by back-to-back atmospheric rivers of rain and spilled rocks, trees and mud across the highway and into the Siletz River. Three homes and their contents were also knocked into the river and some debris from those floated down the Siletz and landed on the beach at the river’s mouth.
Now, with up to five inches of rain Thursday and the threat of flooding on the Siletz, officials remain on edge about whether the slide could continue or even expand because it is roughly half the size of a much larger ancient slide there.
Although not heavily traveled, Highway 229 is an important link between the community of Siletz, the rural areas around it and Gleneden Beach and Lincoln City to the north. The slide occurred between mileposts 14 and 15, the mid-point between the two communities.
“Our crews really got their first on-scene look at it just days ago and they’ve deemed it still very, very unstable,” McCartt said. “We know it hasn’t settled yet and with wet weather and high winds the rest of the week, there’s a good chance it will continue to move.”
Crew members walking toward the slide reported hearing trees cracking.
And while it’s still unknown what condition the highway may be in, or exactly how much debris might have settled on top of it, early indications are that even a small army of dump trucks won’t be enough to tackle the job once things dry out. Crews have deduced that from drone images that show the slide’s downward path toward the river. Most startling, McCartt said, are shots of the middle part of the landslide, where a large swath of upright trees now stand where the road should be.
“That’s not where those trees started that morning,” she said. “What we’re looking at is a raft that floated down that slide that left all of the trees perfectly upright. The slide is so deep that their roots weren’t affected at all. That’s the best indication we have at this point that the slide is awfully, awfully deep.”
When not if
The slide began on property owned by Weyerhaeuser above Highway 229 and continued down to the properties below the highway and into the river. Weyerhauser representatives have been notified and are evaluating their property, according to the Lincoln County Sheriff’s Office.
But even in a state with tens of thousands of ancient and modern landslides, the size of the Highway 229 slide stands out for its size, said Bill Burns, an engineering geologist with the Oregon Department of Geology and Mineral Industries.
“It’s definitely a little unusual for us to have a slide that size move like this,” he said. “And among all these slides, this one decided that last week was its time.”
Worsening the situation is the geologic nature of the Coast Range itself, Burns said. Its main formations are marine mud stones, which are soft and not usually supported by large volumes of heavier rock. That makes the Coast Range extremely susceptible to slides.
Toss in two atmospheric rivers, separated by only a single day, and the chances of a major slide increased dramatically.
“The soils in that area,” he said, “simply did not have enough time to even begin to drain.”
With a third atmospheric river hitting the area Thursday, Burns said he and others remain anxious.
“Less than a week’s gone by since the slide and here we are looking at another one,” he said. “We are very concerned.”
Vigilance pays
Although this particular highway will remain closed for the foreseeable future, motorists driving elsewhere in the Coast Range should pay close attention if they see, for instance, rocks lying in the road.
That could be a sign that things are moving and shifting in the hillside above, portending another possible landslide, said Scott Burns, an emeritus professor of geology at Portland State University.
“Highway and forestry crews are driving up and down these roads a few times a day to look for more rocks coming down,” he said. “It’s just a fact of life in Oregon that steep slopes are prone to sliding.”
He noted, also, that people should pay close attention any time they are approaching coastal creeks and streams this time of year.
“They are so dangerous and fast-moving,” Burns said. “And there’s a lot more in them than just water. Streams are full of rocks, soils and other debris, and folks just need to be really careful about getting too close to them.”
Terra Denney is seeing that daily from her vantage point at Chinook Bend RV Resort, located along the Siletz River about 11 miles downstream from the landslide.
“There is just so much debris floating right by us,” said Denney, the business’s assistant manager. “Freezers. Refrigerators. Trees. An entire house. Thankfully, it’s all missed our docks so far.”
This week, for the first time in Denney’s memory, the 11 occupied trailers on the property’s lower portion once again had to be hauled up to the top of the property to avoid possible flooding Thursday.
“But, really, we’re pretty used to be flooding part,” she said. “What we’re not used to are the mudslides. This is the worst I’ve ever seen it and it’s been really, really scary.”
- Dana Tims is an Oregon freelance writer who contributes regularly to Lincoln Chronicle and can be reached at DanaTims24@gmail.com