Cause, Timeline Undetermined After ‘Catastrophic’ Slide on Road to Mount St. Helens

A massive landslide on Sunday night took out a section of the upper portion of state Route 504, also known as Spirit Lake Highway.

As of Tuesday morning, only one thing was certain: It’s going to be a long time before travelers can make it up to the Johnston Ridge Observatory or other upper reaches of the road, which takes drivers from Castle Rock to Mount St. Helens.

A news release from the Washington State Department of Transportation (WSDOT) on Tuesday afternoon stated the cause of the slide and the timeline for the road’s repair were still yet to be determined. 

The release did provide more detail on the disaster, in which no people were hurt but several were trapped on the remote half of the road overnight. Those people and one dog were rescued by the King County Sheriff’s Office. 

WSDOT stated the debris from an adjacent hillside fell about 2,000 feet and “covered the roadway with rock, mud, ice and water, causing catastrophic damage to the Spirit Lake Outlet Bridge.”

Brad Clark, WSDOT southwest region maintenance manager, said due to the ongoing “geological instability” in the area, it’s too soon to say if crews will be able to safely work up on the road, let alone the timeline for its repair.

For the foreseeable future, the highway will be closed at milepost 43 near the Science and Learning Center, which overlooks Coldwater Lake. This means access to the lake and the observatory will not be available. 

“There is no detour available. WSDOT strongly encourages visitors to not venture beyond the closure location due to the severity of the unstable hillside – the closure is in place for everyone’s safety,” the release stated.

While the cause is yet to be officially determined, WSDOT’s initial assessment was that unseasonably hot temperatures likely drastically melted the snowpack and the extra liquid oversaturated soils and overfilled the channels of the slopes, causing debris to join high water, which built up and then broke free, rolling downstream washing out the 85-foot bridge span and roadway.

“Travelers should plan for the highway to be closed for an extended period,” the release read.

While neither access point has opened for the season, trips to Mount St. Helens this summer will still be possible at Windy Ridge via Randle on the northern side of the mountain and to the Ape Cave on the southern side via cougar.

To check the latest traffic issues, visit WSDOT’s recently updated real-time travel map at https://wsdot.com/Travel/Real-time/Map or follow WSDOT’s southwest Washington-area Twitter account. To stay up-to-date with which Forest Service facilities are open, check out the GiffordPinchot National Forest website.