New video shows the Rattlesnake Ridge crack getting larger


A newly released report says roughly 4 million cubic yards of rock and dirt could continue inching its way down Rattlesnake Ridge for years, if not decades, and is unlikely to become a fast-moving, catastrophically damaging landslide.
The report by a Seattle-based consulting company hired to assess earlier studies largely backs the previous reports, saying it’s improbable rockfall would reach Interstate 82 and “very improbable” it would reach the Yakima River.
“The Rattlesnake Ridge landslide should be treated as a serious threat to public safety, but one that is both predictable and manageable,” according to the report completed by Wyllie & Norrish Rock Engineers, which was hired by the state to provide an independent review of earlier reports, including that prepared by a Portland firm hired by Columbia Asphalt, which operated a quarry at the base of the slide.
At a speed ranging from less than 1 inch per day to 1.4 feet per week, the report said there will be little threat to surrounding roads and buildings.
Conversely, the report said there is less than a 5 percent chance that the slide will move at potentially life-threatening speeds of more than 142 feet per day.
While noting “it cannot be stated, unequivocally,” that the landslide will not move rapidly, the report said there would likely still be enough warning to allow adequate time for evacuations and detour implementation.
Late last year, officials predicted the landslide could occur by mid-January. That estimate was later revised to sometime in early March and most recently officials said they no longer were necessarily looking at an imminent threat. The slide — which is moving at a rate of 1.7 feet per week — hasn’t stopped moving, but isn’t gaining speed.
If the slide continues to move at this rate, the report said, it could take years for the slide to begin falling.









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