To keep a closer eye on the hillside's western flank, which has few instruments, WSDOT recently launched twice-weekly laser surveys. So far, they've measured about 5 feet of bulging compared with images from 2015, Struthers said. That's not surprising and doesn't raise any alarms about a major failure in that area, he added.
State agencies and Cornforth Consulting are developing run-out models that show how far and in which direction the slide could travel under different scenarios, said State Geologist Dave Norman, of the DNR.
And last week, DNR and WSDOT hired an independent contractor, Wyllie & Norrish Rock Engineers, to analyze the monitoring data, observe the slide and provide a second opinion.
"We want to be sure another top-notch outfit looks at it," Norman said. "This is really important and we want to get it right."
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GRAPHIC (for help with images, contact 312-222-4194): Landslide