|Bertha before drilling began in July 2013. CreditTed S. Warren/Associated Press|
It's been 18 months since I first blogged about Seattle's big dig project: the tunnel to replace the Alaskan Way viaduct. This was a huge project including the world's largest drill bit with a 57.5 feet diameter. I remember reading a few months ago about the bit hitting an unknown object that caused it to stall. What's going on now?
|A hole dug by Bertha, the tunnel-boring machine that went dormant last December.CreditDavid Ryder for The New York Times|
In a recent NY Times article, we learn that the pipe it hit back in December caused damage that has stalled the drill until next March. Rescuing the bit required the drilling of a shaft to reach the damaged area, shoring up the tunnel it already dug to prevent it from collapsing, replacing huge parts then making further repairs.
|A crane hoisting a tunnel-boring tool at a construction site where a large shaft is being dug to get to Bertha. CreditDavid Ryder for The New York Times|
One of the biggest problems is the size of everything involved. When everything is scaled up, the cost and time to repair problems scales up exponentially. The eighteen month delay and hundreds of millions in budget overruns all stem from an eight inch diameter steel pipe that nobody involved in the project knew was in the way of Bertha. I'd love to see the official risk management of this project.