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Bertha to resume digging in March 2015

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. 

Repairing the SR 99 tunneling machine

Seattle Tunnel Partners is building a 120-foot-deep pit that will allow crews to access and repair the machine, which is stopped about 60 feet underground between South Jackson and South Main streets. When the pit is complete, the machine will tunnel forward into it. Crews will then partially disassemble the machine, and make repairs and enhancements. Below are links that illustrate STP's plan to resume tunneling by the end of March 2015.

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.