Temporary ‘fix’ after landslide on Spirit Lake Highway has failed, WSDOT says

Culvert failure will extend closure of Johnston Ridge Observatory indefinitely


Johnston Ridge, which offers the best crater viewpoint in the Mount St. Helens National Volcanic Monument, is unlikely to be open any time soon, despite initial optimism from the Washington State Department of Transportation (WSDOT) that the road could be used for the 2024 season.

After what agencies described as a “catastrophic” landslide last May along state Route 504, also called the Spirit Lake Highway, WSDOT hired an engineering firm to install a temporary, one-lane bypass road over culverts.

In an email to local lawmakers and stakeholders on Wednesday, WSDOT broke the bad news. A “localized event,” wrote Carley Francis, Southwest Region administrator for WSDOT, caused the culverts to collapse. The agency was made aware of the incident on Nov. 5. WSDOT also updated its website with information about the culverts on Thursday.

In the following days, Francis said, the department was able to assess the site and discover the culverts’ failure was not related to the initial landslide, nor to recent seismic activity at Mount St. Helens recorded by the United States Geological Survey (USGS).

“This culvert failure was related to rainfall, flow of water and erosion at the roadway location itself,” Francis wrote.

The incident had “no impact” to current travelers on the road, which remains closed before the slide. Upper stretches of the Spirit Lake Highway are typically only open from late spring to late summer.

The event is not believed to have impacted the Spirit Lake outlet tunnel, which runs under the roadway.

However, “out of an abundance of caution,” Francis wrote, “to remove the culverts, guardrail, asphalt and fill material that made up the temporary access to avoid the possibility of impacts to the Spirit Lake outlet tunnel. Currently, we are working quickly to begin an emergency contract to complete this work. Our greatest priority right now is protecting the flow of water through the outlet tunnel, which is critically important to downstream communities.”

The initial fix on the highway allowed for seven vehicles stranded on the wrong side of the May landslide to be evacuated from Johnston Ridge and offered monument staff access to the site.

According to previous reporting by The Chronicle, the landslide, dubbed the “South Coldwater Slide,” occurred when an early May heatwave melted the mountain’s snow in record time, oversaturating the ashy, young soil near Coldwater Lake.

Around 9 p.m. on Sunday, May 14, debris from a hillside just upstream pummeled the highway and washed out an 85-foot bridge. The event lasted 30 minutes. With around 300,000 cubic yards of debris sliding downhill, it was enough to cause a blip on USGS seismometers.

Despite the massive scale of the May landslide, quick work of agencies involved meant public access to the Johnston Ridge Observatory (JRO) was, as Francis wrote, “optimistically being discussed for some time in 2024.”

Erosion of the temporary bypass, Francis wrote, will negatively impact that timeline.

“The next few months will include many discussions across multiple parties regarding timelines for temporary and permanent access to JRO. At this time, there is no timeline for public access being restored to JRO,” she wrote.

Visitor centers, trails and viewpoints remain open to the public (depending on seasonal availability), including Mount St. Helens Visitor Center at Silver Lake, the Forest Learning Center, Elk Rock and Castle Lake Viewpoints, the Science and Learning Center at Coldwater, Coldwater Lake Recreation Area, Hummocks Trail and the South Coldwater Trailhead.