Massive Rockslide Shuts Down SR 20 Near Diablo Lake

Huge boulders are now sitting across State Route 20 North Cascades Highway, forcing a full shutdown near Diablo Lake.

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The Washington State Department of Transportation reported the slide about four miles west of the seasonal closure point, leaving the highway impassable until further notice.

WSDOT Warns This is Not Your Typical Debris Cleanup

The landslide is not just loose gravel or a few scattered rocks. Crews say some of the fallen debris measures over 200 feet in size and weighs tons. That is the kind of obstruction that turns a routine cleanup into a long and major operation.

Officials say the slope is now considered stable, but the sheer size of the rocks in the roadway means removal will take time and a well-thought-out plan.

Before any heavy equipment moves in, geotechnical engineers carefully evaluate the site. That step is critical to ensure there’s no additional risk of rock falling once crews start working.

Until that assessment is complete, no removal work can begin.

What Washington State Travelers Need to Know

Drivers heading east on SR-20 can only go as far as Colonial Creek before having to turn around. There’s no estimated reopening time yet, so if you were hoping to cross the North Cascades, you will need to plan an alternate route.

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Stay alert for updates from WSDOT, and if you’re heading into the mountains, always check road conditions before you go.