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Preventing landslides

What’s not to love about Seattle’s hills, with their great views of the water and mountains?

Well, here’s something: landslides.  

Depending on the amount rain and their intensity,  landslides can be a big problem, causing major damage to public and private property.  

Last year SDOT’s Street Maintenance crew responded to more than 20 landslides.   The most severe landslide last year was on Lake Dell Ave, an arterial with a bus route, which was closed for ten days due to three separate slides on the same slope in one day.

Take a look at how SDOT recently secured a chronic landslide area:

The west side of Lakeside Ave S, just a few blocks north of I-90, had sloughed onto the street for over a decade, requiring Street Maintenance crews to clean debris from the street every year.  Slides here are an extra concern because the road is curved, limiting sight distance.  A serious slide here could block the street, cause a serious accident and eventually undermine a home above.  Last winter the problem got worse and it was time for a long-term fix.

BEFORE: Lakeside Ave S with debris from landslide

To prevent future slides, this fall SDOT’s Roadway Structures crew built a wall.  A serious wall– 42 feet long, three to seven feet high, made of reinforced concrete panels and steel piles.  This thing is expected to last 100 years.

Before building the wall, crews removed about two dump truck loads (about 20 cubic yards) of debris which had sloughed off the slope.  SDOT will no longer need to spend resources  to clean up landslide debris here each year.   Most importantly, everyone is safer. 

AFTER: New wall prevents slides onto the street