Seattle Tunnel Megaproject

Dramas while building the world’s largest earthquake-proof tunnel!

Ram Education team has attended a fascinating presentation on the Seattle tunnel megaproject. Thank you and the Australian Institute of Project Management AIPM.

The tunnel, which replaced the ageing and earthquake-prone Alaskan Way Viaduct, was dug by the Tunnel Boring Machine “Bertha” – an US$80 Million, 6,100 Tonne monster, with a cutting diameter of 17.5m. Like all megaprojects, there were many challenges. At one point, 330m into the planned 2,830m route, Bertha got stuck! Apparently, a steel well casing, used to measure groundwater, damaged the main bearing seal system, causing the machine to overheat and shut down.

Accessing the machine, deep underground, for repairs took 2 years! The Washington State Department of Transportation (WSDOT) sued the contractor Seattle Tunnel Projects (STP) for delay, while STP sued WSDOT for the US$125M repair bill, claiming that WSDOT had failed to inform them about the steel well casing.

The photo shows the access pit, which enabled the damaged front end of Bertha to finally be lifted to the surface for repair. The new tunnel carries 2 lanes of traffic in each direction and is able to withstand a Richter 7.0 earthquake.

Posted in
Scroll to Top