New Study Says Rattlesnake Ridge Could Take ‘Years’ to Fully Fall

According to new data released Wednesday, officials now say it's possible the huge slab of earth and rock at Rattlesnake Ridge by Yakima could even hang on for years, gradually working it's way down the slope.

A study was prepared by the engineering firm of Wyllie & Norrish Rock Engineers to be used by the Washington State Department of Transportation. They wanted to find out what dangers Interstate 82 is facing if the mountain comes down.

Although it's been sliding at the rate of about a foot and a half a week, the study actually says it's slowed slightly recently. The study says there's about a 5% chance of total failure of the hillside, meaning 4 million cubic yards of soil would slide down, perhaps onto the Interstate and evacuated properties below.

But the study also says it could take years or even decades to full fail. The mountainside is made up of basalt rock, and has separated a total of about 12 feet wide, the crack running along the top near the crest of the ridge.  They also say it's likely a lot of material could be "bulldozed" in a series of smaller failure events.

The study also recommends a fully deployed automated data recording and warning system be put around the perimeter immediately.