The Seattle Times » In January 2016, a geotechnical expert for the Washington State Department of Transportation (WSDOT) warned officials of possible over excavation and ground loss one day before a sinkhole appeared 110 feet behind the tunnel boring machine’s cutting face. WSDOT and their consulting engineers are concerned about the contractor’s ability to maintain soil consistency, and the potential for additional sinkholes while the tunnel boring machine, known as Bertha, digs under downtown Seattle and the existing Alaskan Way Viaduct.
