Project overview
Shortly after 9 p.m. on Mother’s Day, May 14, 2023, more than 300,000 cubic yards of debris slid about 2,000 feet down a hillside above SR 504 near milepost 49. The slide buried the highway in rock, mud, ice and water and destroyed the 85-foot Spirit Lake Outlet Bridge.
Starting Monday, April 20, Washington State Department of Transportation contractor crews will begin work to permanently rebuild the bridge and roadway, restoring access to the upper stretch of SR 504 and the Johnston Ridge Observatory at Mount St. Helens. Construction is expected to be complete in fall 2026.
What to expect
What to expect
Crews will build a new two-lane roadway and bridge designed for the area’s challenging terrain and changing conditions. The new bridge will be similar in width to the original structure, but longer and built to last.
What happened
Shortly after 9 p.m. on Mother’s Day, May 14, 2023, more than 300,000 cubic yards of debris slid about 2,000 feet down a hillside above SR 504 near milepost 49. The slide buried the highway in rock, mud, ice and water and destroyed the 85-foot Spirit Lake Outlet Bridge.
Within two months, crews cleared the debris and built a temporary bypass road so vehicles stranded at Johnston Ridge Observatory could be recovered. The unstable landscape and harsh winter weather conditions caused the temporary structure to fail after four months due to erosion, water flow and shifting ground.
To ensure safety, WSDOT removed the failed structure and materials until a permanent solution could be built.
Looking ahead
Work is expected to be complete in fall 2026. After construction, the U.S. Forest Service will begin work to restore Johnston Ridge Observatory, including power and other essential repairs, before it can reopen to the public. Once finished, travelers will again be able to drive the full length of SR 504 and visit the observatory to experience the dramatic landscape shaped by the 1980 eruption of Mount St. Helens.
Planning a visit to the Gifford Pinchot Forest
Several visitor centers, trails, and viewpoints remain open to the public on SR 504 (subject to seasonal closures and winter hours) 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. These activities in no way impact current travelers as SR 504 is closed at the winter gate, milepost 45.2, and there are no impacts to U.S. Forest Service facilities other than JRO.
Please visit the Gifford Pinchot National Forest website for information about accessing U.S. Forest Service facilities.
Image shows location of debris slide that happened along SR 504 at milepost 49, destroying the Spirit Lake Outlet Bridge and highway. The road is currently closed at milepost 45.2 at the winter gate.
In 1980, the north face of Mount St. Helens slid away and triggered a massive eruption that created a lahar, or a slide made up of wet volcanic mud and debris, that devastated the North Fork Toutle River. This event caused extensive damage to approximately 25 miles of SR 504, including seven of the eight major bridges, leaving only the Kid Valley bridge intact due to its clearance. The segment between Toutle and Kid Valley was buried under 6 feet of sediment, leading to the closure of the highway beyond Toutle. To manage the situation, Weyerhaeuser installed a roadblock and turnaround loop.
Recognizing the significance of this area, the federal government officially designated it as the Mount St. Helens National Volcanic Monument in 1982. The state government also honored the victims of the eruption by designating SR 504 as the Spirit Lake Memorial Highway. A visitor center was later established at Silver Lake in 1987 to serve growing tourism.
In pursuit of improving access and visitor experience, an ambitious highway reconstruction project began in 1988. The Science and Learning Center at Coldwater Creek (milepost 43) opened in 1993, followed by the Johnston Ridge Observatory in 1997. Located at the end of SR 504, just five and a half miles from the crater created by the 1980 eruption, it provides sweeping views of the volcanic landscape.
These efforts extended SR 504 by approximately 30 miles, reaching milepost 51 and opening new access and recreation opportunities along the highway.
More recently, a temporary structure was installed after the landslide destroyed the Spirit Lake Outlet Bridge to restore limited access to the area, but it failed after four months due to geotechnical and hydraulic challenges and the dynamic conditions of this volcanic site.
Given the harsh winter weather conditions and site dynamics, additional temporary solutions such as a Bailey bridge were not feasible. They would significantly increase cost and delay a permanent solution and would also be at risk of similar failure.
Out of an abundance of caution, WSDOT removed the culverts, guardrail, asphalt and fill material that made up the temporary structure. Access to the upper stretch of SR 504 was closed until a more permanent solution could be constructed.