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Landslide Information for Mercer Island

MI Landslide Example
Dec 16, 2015 – As a result of the duration and intensity of last week’s multiday rain event in the region, Mercer Island witnessed a significant landslide at SE 46th Street on Wednesday morning, December 9, involving three neighboring properties and no injuries.

As is customary in these situations, as soon as the City learns of such an event, the lead Building Official travels directly to the affected site to assess the damage firsthand, and determine whether the buildings involved are still safe for occupancy. Two of the three property owners were unaware of the incident until informed by the City. 

Due to the ongoing risks posed by the possible expansion of the landslide, and supporting information from the City’s GIS mapping data, all three properties were "red tagged" as unsafe at this time, obliging residents to find alternative accommodations. The City provides emergency services and support in these situations, and ensured that all families had access to housing elsewhere.  

Under advice from the City, all of the involved owners began to contact State-licensed geotechnical engineers for a detailed evaluation and suggested mitigation measures.

The Island typically sustains 6 to 15 landslides per year, which are often exacerbated by many consecutive days of heavy rain.

  • Learn more about landslides and forecasting at this City webpage
  • Read and download a City landslide factsheet here
  • View the City's landslide hazard map here



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