On Sunday evening, May 14, around 9 p.m. a landslide caused significant damage to the upper portion of State Route (SR) 504 at milepost 49, leading up to the Johnston Ridge Observatory north of Mount St. Helens. The event followed a recent warming trend and significant snowmelt.
The slide washed out an 85-foot bridge, damaged the roadway, and severed power to Johnston Ridge Observatory. No one was injured because of the incident and twelve members of the public who were stranded overnight at Johnston Ridge Observatory were safely flown out the following morning.
In coordination with federal agencies, the Washington State Department of Transportation WSDOT closed the highway to all travelers. Travel along SR 504 remains open with multiple scenic viewpoints up to milepost 43 near the Science and Learning Center at Coldwater.
There is currently no access to Coldwater Lake, the Hummocks Trail, and the Johnston Ridge Observatory. For safety, WSDOT and federal agencies strongly encourage people not to venture beyond the highway closure location due to the severity of the unstable hillside.
The USDA Forest Service is in the process of exploring alternative options for visitors who would like to visit the north side of the Mount St. Helens National Volcanic Monument this summer and develop a plan to manage the influx of visitors in a safe manner. Several other visitor centers located along SR 504 remain open to the public, including scenic viewpoints where visitors can see Mount St. Helens and learn about the history, eruption, and recovery of the volcano. As the snow melts and US Forest Service roads open for the season, additional sites on the Monument and surrounding communities will begin to open for visitors to explore.
WSDOT and federal agencies are working together to assess the slide area and develop next steps. Due to continued landslide instability, data collection is being conducted from the air.
WSDOT conducted a fixed wing aircraft LIDAR (Laser Imaging, Detection and Ranging) flight over the area on Friday, May 19 to gather preliminary data, weather permitting. This is an important step in collecting data to help inform when on-site access, cleanup and work can begin. It is too soon to tell when crews may be able to access the slide from the ground or when the highway may reopen.
A National Incident Management Organization team arrived on Friday, May 19 to support coordination across agencies.
Source: U.S. Forest Service