Seattle InSAR Interactive Map
Start Sinkhole Big Bertha Issues Subsidence


Tunnel boring began July 30, 2013, with a scheduled completion date of December 2015


On January 12, 2016, a sinkhole formed 35 feet north of the vertical recover shaft. The project was put on hold by the governor of Washington on January 14, 2016.

Big Bertha Issues

Tunneling continued until December 6, 2013, when the machine unexpectedly stopped operating. In November 2014, workers began digging a vertical recovery shaft that required groundwater pumping at a rate of 700 gallons per minute.


As groundwater pumping took place starting in December 2014, widespread subsidence occurred throughout the downtown area at a magnitude of up to 60 millimeters. South King Street and some of the neighboring buildings experienced visible damage. Traditional surveying measured smaller amounts of displacement due to the reference points also subsiding.