Follow Bertha

Seattle Tunnel Partners working to repair Bertha

In summer 2013, Bertha, the world’s largest tunneling machine, began digging the SR 99 tunnel beneath downtown Seattle. In December 2013, Seattle Tunnel Partners, the contracting team hired to design and build the tunnel, stopped excavation approximately 1,000 feet into the dig after measuring increased temperatures in the tunneling machine. While investigating the cause of the high temperatures, STP discovered damage to the machine’s seal system and contamination within the main bearing. 

Bertha lifted to the surface for repairs

On March 30, 2015, Seattle Tunnel Partners safely placed the front end of the SR 99 tunneling machine on the repair platform located just south of the access pit. The piece - along with three others - was lifted from the 120-foot-deep pit crews built to access and repair the machine. With the necessary pieces now at the surface, STP is preparing to make repairs and enhancements. Below are links that illustrate STP's plan to resume tunneling. The latest schedule is available here.

Live view of construction

Construction is hard to see in person because crews built a wall to shield neighbors from construction noise. The best view of STP’s work is from our time-lapse camera. Click on the "SR 99 tunnel access pit" camera in the grid below to watch crews as they work to access and repair Bertha, or check out other viaduct-related construction happening elsewhere along the SR 99 corridor.