ROAD CONSTRUCTION: Bertha held up again by overheating under Seattle

Seattle Tunnel Partners (STP) pushed the S.R. 99 tunneling machine forward approximately 2 ft on Tuesday, Jan. 28. Moving the machine forward allowed crews to further test the functionality of the machine and determine if they could resume full­production mining. It also created sufficient space to build the next concrete tunnel liner ring on Wednesday, Jan. 29.

When the machine moved forward, crews saw indications of above­normal temperature readings in part of the machinery, similar to readings encountered before crews initially decided to stop mining on Dec. 6. On Wednesday, STP made adjustments and mined an additional 2 ft. The above­normal temperatures persisted, and STP made the decision to stop and perform further evaluations.

Over the next week, outside tunneling experts brought in by WSDOT will meet with the WSDOT and STP project teams to review the situation and determine the best path forward.

STP crews and tunnel engineers are operating the world’s largest tunneling machine in complex conditions. Although their investigations to date have provided a great deal of information, we will not be able to definitively identify the issue or issues facing the machine until tunneling experts complete their review. We will provide additional information as it becomes available.