Feb. 18 afternoon update: Bertha digs on
Since mining resumed at 10:15 p.m. Tuesday, Bertha has successfully moved forward more than six feet and work is progressing as planned. Crews stopped mining this afternoon to begin building the SR 99 tunnel’s 151st concrete ring. Mining will resume after the ring has been built.
Seattle Tunnel Partners and tunneling machine manufacturer Hitachi Zosen are continuing to follow strict protocols as they mine through the access pit’s southern wall. These protocols are designed to prevent overheating or further damage to the machine as it mines through 20 feet of unreinforced concrete to reach the interior of the pit.
We continue to closely monitor the surrounding area as this work proceeds.