Western Washington University

04/13/2026 | News release | Distributed by Public on 04/13/2026 10:24

One Quick Question: Why is it taking so long to reopen I-5

One Quick Question: Why is it taking so long to reopen I-5?

April 13, 2026

A landslide closed all lanes of I-5 north near Lake Samish on March 19. Photo courtesy of WSDOT.

After a landslide blocked both lanes of I-5 North on March 19, the interstate has remained closed as roadwork crews work to remove debris and stabilize the slope. After weeks of daily work, I-5 is set to reopen on Thursday, April 16, according to the Washington Department of Transportation.

After two weeks of detours, some may be wondering, "What's taking so long?"

We asked an expert.

Professor of Geology Bob Mitchell answers: Why is it difficult to stabilize a slope after a landslide?

Roadwork continues on I-5 to reopen the freeway after a landslide on March 19. Photo courtesy of WSDOT.

"Unlike human-made materials like concrete where engineers know the strength parameters to a high degree of precision when designing structures like the Environmental Studies Building, the strengths of Earth materials are much more uncertain.

Geologic deposits are inherently variable in their composition and evolve over time. The deposits that define the Chuckanut Formation were originally formed by rivers and experienced 50 million years of transformation. Tectonic forces altered the sediments into rock materials (sandstones, siltstones, coal) and deformed them into the tilting, fractured formations that define the relief around Bellingham. Add on the stress impacts of multiple ice ages and ground shaking due to earthquakes and you can appreciate how characterizing the strength and integrity of these rock materials on dipping slopes presents a very difficult challenge.

As you examine the photos of the I-5 landslide, note the large range of block sizes and shapes and the nature of the irregular, dipping surfaces from which they were sourced. Engineering geologists and geotechnical engineers working to make the rock slopes safe, are also under the constraints of professional licensing designed to protect the health and welfare of people and property, so care and caution is taken to reduce the risk of subsequent failures.

After removing debris and scaling the loose remains off the slope, the remaining rock masses are secured with rock bolts by drilling through them into the deeper, hopefully more- stable rock.

So, if you are delayed in traffic due to the I-5 landslide, please be patient knowing that the engineers and work crews are doing their best under extreme time constraints to secure a complex rock mass to keep you and other I-5 travelers safe.

So, if you are delayed in traffic due to the I-5 landslide, please be patient knowing that the engineers and work crews are doing their best under extreme time constraints to secure a complex rock mass to keep you and other I-5 travelers safe."

Mikayla King, '17, covers the College of Science and Engineering and Woodring College of Education for University Communications. Reach out to her with story ideas at [email protected].

Western Washington University published this content on April 13, 2026, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on April 13, 2026 at 16:24 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]