A timeline of key dates in Seattle Tunnel Project:
January 2008 - Washington Gov. Christine Gregoire announces state will take down Alaskan Way Viaduct in 2012.
January 2009 - State of Washington, King County, city of Seattle and Port of Seattle announce agreement to replace Alaskan Way Viaduct with bored underground tunnel
May, 2009 - Governor Christine Gregoire signs measure authorizing $2.8 billion in state funds for tunnel project.
April, 2013 - The world's largest tunneling machine, now christened "Bertha", arrives in Seattle.
July 30, 2013 - Bertha begins drilling. Initial plans call for drilling to take 14 months.
July-December, 2013 - Bertha travels 9.270 feet of planned 9,270 feet.
December 3, 2013 - Bertha strikes 8-inch-diameter steel pipe after tunneling 59 feet.
December 6, 2013 - Bertha components shut down during attempts to drill at high power. Drilling halted.
December 7, 2013 - Seattle Tunnel Partners operators try to get Bertha moving again. Drill running at elevated temperatures. Drilling remains stopped.
January 3, 2014 - WSDOT reveals steel pipe to blame for tunnel stoppage.
January 25, 2014 - Seattle Times reports steel pipe struck by Bertha was put there by WSDOT engineers to study groundwater and included in plans provided contractor prior to tunnel bid submission.
January 28-29, 2014 - Bertha drills two feet each day as STP restarts drill and tries to determine cause of overheating problems. Drilling halted again.
February 7, 2014 - WSDOT announces Bertha seals and bearing damaged, likely causing overheating problems, no schedule for repairs or resumption of drilling.
February 28, 2014 - Seattle Tunnel Partner project director Chris Dixon says contractor hopes to complete repairs and resume drilling by September 1.
March 2014 - STP continues working with Bertha manufacturer to determine best way to repair drill and resume operations. Plans call for 120-foot-deep pit ahead of drilling machine to facilitate repairs. WSDOT digs 60 narrow test holes to check for historic artifacts ahead of repairs.
April 9, 2014 - Seattle tunnel critic files lawsuit to stop repairs on Bertha.
April 21, 2014 - WSDOT, STP announce tunneling will not resume until March 2015.