Digging a 2-mile tunnel to replace the original 50-year-old double-deck roadway was very controversial and estimated to cost $6.4 billion. Boring of the tunnel with the world's largest boring machine, "Bertha", began on July 30, 2013 and was originally scheduled for completion in December 2015.Work was halted after just 4 months and 1,083 feet into the 9270-foot-long route after cutting blades were damaged after encountering a steel pipe. Over the next 2 years, a recovery pit was dug from the surface in order to access and lift the machine's cutterhead for repair and partial replacement. (You can watch time-lapse of the repair dig here: www.lifeleak.com/view?i=667_1454536475 .)Bertha resumed tunnel boring in December 2015, then stopped again in January 2016 due to a sinkhole that formed above Bertha. Tunneling resumed again in February 2016. The tunnel in now expected to be completed in early 2019.Washington State Dept of Transport