Officials monitor events at the Rattlesnake Ridge slide (video)

Officials continue to monitor the conditions in Yakima County related to a 250 foot fissure opening up along the top of Rattlesnake Ridge at Union Gap immediately south of Yakima.

Affected Area
Affected Area (click or tap image to enlarge)

Yakima Valley Office of Emergency management has closed at least one road (Thorp Road) leading through the gap for safety reasons  and WSDOT is said to be monitoring the situation closely.

Interstate 82, Highway US97, Northern Pacific Railroad lines, Irrigation District water lines, and the Yakima River pass through the narrow gap just south of the City of Union Gap.


According to the Yakima Herald, Yakima County officials said they can’t definitively predict the scope of an expected landslide on Rattlesnake Ridge, where massive cracks have opened several hundred feet above Thorp Road. However, officials also said a landslide could be limited in scale. Geologists have been monitoring the slow-motion movement of soil in the area since October.

Horace Ward, Yakima Office of Emergency Management senior emergency planner, said the evacuation status was upgraded to a “level 3” because officials monitoring the crack predict “something could happen” in the coming weeks.

“We’d much rather be safe than sorry,” Ward said.

A level 3 evacuation means residents are advised to leave the area, Ward said. A level 2 status urges residents to be prepared to leave their homes.

PNSN SEIS Stations
PNSN SEIS Stations (click or tap image to enlarge)

The Pacific Northwest Seismic Network (PNSN) mobilized to install portable monitoring instruments near the site on Tuesday January 2nd after several inquiries from concerned parties in the area. The monitoring equipment will measure movement and speed of the slide.

Interstate 82 is still open in both directions in Union Gap. WSDOT will keep the road open as long as it is safe for travelers. Transportation officials are warning drivers to watch for falling rocks on Interstate 82 in both east and westbound lanes between mileposts 37 and 39 south of Union Gap.

As an added precaution, large freight containers have been brought in and placed as a barrier between the Interstate and the slide area to protect against potential falling debris.

A detour plan is ready to be put in place if the hillside begins to slide and travel on the roadway becomes too dangerous.

As of right now, no falling rocks have reached the roadway.


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