Visitors to Johnston Ridge Observatory should expect an extended closure of the highway after landslide washed out bridge
TOUTLE – The upper portion of State Route 504, which takes travelers to the Johnston Ridge Observatory located within the Mount St. Helens National Volcanic Monument, will remain closed until further notice following a massive debris slide. Due to the size of the slide and the instability of the hillside above the highway, the Washington State Department of Transportation does not know when the road will reopen.
The highway closed shortly after 9 p.m. Sunday, May 14, when 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. Engineers need to examine the hillside above the roadway and debris below to develop next steps.
“Additional safety analysis is needed, but due to the ongoing geological instability in the area, it’s too soon to tell when we’ll be able to safely do that work,” said Brad Clark, WSDOT Southwest Region Maintenance Manager. “We appreciate everyone’s patience during this emergency.”
Spirit Lake Memorial Highway is closed to all travelers at milepost 43 near the Science and Learning Center at Coldwater. The closure blocks access to Coldwater Lake and the Johnston Ridge Observatory as engineers work to assess the debris flow and ensure for public safety. 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.
WSDOT is working in coordination with the U.S. Forest Service, U.S. Army Corps of Engineers, U.S. Geological Survey, and Skamania and Cowlitz counties in evaluating slope conditions. This work will help inform what steps are needed to stabilize the slope, cleanup, and rebuild the roadway and bridge.
The cause of the landslide is yet to be determined, though initial assessment is that unseasonably hot temperatures likely drastically melted snowpack which 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.
There is currently no timeline for this work. Travelers should plan for the highway to be closed for an extended period.
Drivers can stay informed on the latest traffic issues by visiting WSDOT’s recently updated real-time travel map, or by following 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.
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