Prehistoric ‘Prosser Landslide’ Causes Bumps on I-82 Near Benton City

If you’re from around these parts, you’re likely very familiar with the barrage of bumps on eastbound Interstate 82 between Prosser and Benton City at milepost 91.9. The bumps have been there since the late 80s and the WSDOT hasn’t been able to remedy the problem. You could say, they keep hitting bumps in the road (sorry).

What caused the bumps on Eastbound I-82 Near Benton City?

According to a research paper by Jessica Jamsgard (University of Washington, 2013), the construction of I-82 between MP 82 and 92 was filled with complications from the start because of a prehistoric landslide, known as the Prosser Landslide.

What is an Ancient Landslide?

An ancient landslide is just that, a landslide that took place thousands of years ago but is now stabilized but can still affect the ground’s sturdiness. The image above shows the edges and how the landslide flowed down toward the Yakima River.

Why Can’t the Bumps on Eastbound I-82 Be Repaired?

During the construction of I-82 in 1987, the unstable ground in the area of MP 91, created quite a headache for construction crews and forced them to use stabilizing tactics such as inserting buttresses, adjusting the grading, and realigning the route to try and remedy the problem – to no avail. Over the last 38 years, the WSDOT has improved the situation by using warning signs and lessened the impact the bumps have on drivers and vehicles with new-age tactics, but Mother Earth is still winning this battle. The report is a very dry read, but if you're interested in how the problem has been addressed from start to finish, have at it, it's all right HERE.