Expert: Rattlesnake Ridge not sliding towards river, I-82

Expert: Rattlesnake Ridge not sliding towards river, I-82

UNION GAP, Wash. - Many are wondering of the hazardous effects a Rattlesnake Ridge landslide could have on nearby communities and even the Yakima River.

Action News spoke with George Machan, a geotechnical engineer with Conforth Consultants for an overview of the tension crack discovered in October of 2017, experts said has caused the slow-moving landslide.

Machan advised the landslide is not moving west towards Interstate 82 and the Yakima River, a concern many have had, but instead south towards the Columbia Ak Anderson Quarry.

Video courtesy of Steven Mack.

He said because the slide is moving eight million tons of rock south, it is moving along the 200-foot deep crevice instead of away.

Machan noted the slide is moving on a relatively gentle slope, and while some break-off could move to the west, rocks would have to travel a great distance to reach the interstate.

He also expects the majority of the landslide will likely stop itself from slipping into the quarry.

The Washington State Department of Transportation is informing drivers while I-82 has not been closed for potential of falling rocks, several agencies are monitoring the road for falling rocks. The areas of concern is milepost 37 to 39 south of Union Gap. Any sign of rock movement will result in an I-82 closure and detour routes would be put in place.

At this time, large freight containers full of concrete have been installed between Thorp Road and I-82 for protection from falling rocks. The containers have been placed as a precaution.

Machan said the county is being careful in practicing these precautions.

He expects most landslide activity will take place between early January and the end of February 2018.

Machan believes the slide is not posing a risk to people at this time, but he and other agencies continue to monitor the ridge for any movement.

Visit the Yakima Valley Office of Emergency Management Facebook Page to follow updates on the ridge.

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