Jan. 21 update: Hyperbaric inspections continue

Posted on Jan 21 2014 3:47 PM

Since hyperbaric inspections began on Jan. 17, crews from Seattle Tunnel Partners (STP) have spent more than 35 hours inside the excavation chamber gathering information about what might have caused increasing resistance at the front end of the machine before tunneling was stopped on Dec. 6.

While the inspections are underway, it is too early to speculate on what led to the tunneling stoppage.

Over the weekend, crews inspected a portion of the cutterhead as well as the cutting tools they were able to access. They also cleaned the spokes and removed a bent piece of metal well casing and plastic PVC pipe. Crews also identified a large boulder or piece of concrete material in a cutterhead opening.

The information from the inspection along with other data will be reviewed by a tunneling operation task force, which has been convened by WSDOT.

These inspections are methodical. Workers are going spoke by spoke to clean off the tunnel muck, inspect parts and make necessary repairs.

Air is being pumped into the chamber to stabilize the ground in front of the machine so crews can safely work in areas that would otherwise be filled with soil and water. After pressure in the chamber was lost, crews spent Sunday re-establishing the required air pressure in the chamber so inspection work could continue. This is a routine occurrence in hyperbaric interventions. A detailed description of this type of work is included in our Jan. 14 update.

Keeping workers safe is everyone’s top priority. STP has a number of safeguards in place to protect crews as they perform their work within the machine. Working under hyperbaric conditions is difficult, but it’s normal within the tunneling industry and has been done on other projects all over the world.

Previous updates

Jan. 17, 2014 update – Crews begin inspecting excavation chamber

Jan. 16, 2014 update – Working with Seattle Tunnel Partners to resume tunneling

Jan. 14, 2014 update – Diving deeper into the tunneling stoppage

Jan. 13, 2014 update – Filling in shaft number three

Jan. 10, 2014 update – Exploratory shaft work continues