Many Seattleites fear ‘the really big one’, a projected 8.7 – 9.2 magnitude earthquake that could hit the Puget Sound and northern West Coast at anytime. But fewer of us realize the danger of the earth opening up beneath our very feet! Sinkholes are a very real danger in Seattle, and can happen without warning and at small to terrifying sizes. Just a year and a half ago, a large hole suddenly opened up between two homes on Queen Anne. And last month, a recycling truck was stuck in a West Seattle sinkhole near 24th Avenue SW and SE Kenyon S.
Only a couple of weeks ago, another sinkhole opened up on Queen Anne in the middle of 5th Avenue. It was three feet wide and required the closure 5th Avenue between West Comstock Street and West Highland Drive in order for Seattle Public Utilities to repair it.
In Seattle’s history, sinkholes have trapped cars and even people, although there have been no casualties. Sinkholes have been a ‘thing’ throughout the city over the past year, and not just because of the drilling caused by Bertha, the drilling machine that’s tunneling below Belltown to replace the Alaskan Way Viaduct.
Why does the city get these sinkholes? Seattle soil isn’t characterized by karst terrain, the type of rock that commonly develops sinkholes. Instead, our sinkholes are caused by aging water and sewer systems underground. According to U.S. Geological Survey geologist Randall Orndorff, “Since these systems are pipes, they act like caves in the natural setting—a void beneath the surface.”
Featured photo source: Q13fox.com