PORTLAND, Ore. (KOIN) – The U.S. Forest Service is in the process of exploring alternative options for visitors who hope to explore the north side of the Mount St. Helens National Volcanic Monument during the summer of 2023 after a landslide caused significant damage to the upper portion of State Route 504 on May 14. 

The highway is currently impassible at milepost 49, which leads to the Johnston Ridge Observatory north of Mount St. Helens. 

The landslide occurred after a recent stretch of warm weather caused snow to melt. The slide washed out an 85-foot bridge, damaged the roadway and severed power to the Johnston Ridge Observatory. 

No one was injured, but 12 people were stranded overnight at the observatory and were flown out the following morning. 

SR 504 remains open up to milepost 43 near the Science and Learning Center at Coldwater. 

However, with the closure in place, there is currently no access to Coldwater Lake, the Hummocks Trail and the Johnston Ridge Observatory. 

The Washington State Department of Transportation asks people to not venture beyond the highway closure because of the unstable hillside. 

The U.S. Forest Service is working on a plan for how to manage the influx of summer visitors safely. They encourage people traveling to the area to explore the visitor centers along SR 504 that remain open. There are still scenic viewpoints that allow visitors to see Mount St. Helens and learn about its history and eruption. 

As the snow continues to melt, the U.S. Forest Service said more roads will open for the season. 

WSDOT and federal agencies are assessing the slide area. WSDOT said it performed a lidar flight on Friday to get a 3D representation of the slide. 

On Monday, WSDOT engineering geologists collected data on the ground that they can use along with the lidar information. 

WSDOT expects it will have more information to share in the middle of next week.