WSDOT said it conditionally lifted the "suspension for cause" that halted mining and barging-related activities last month following two safety incidents. "As part of the conditions for lifting the suspension for cause, STP will be permitted to tunnel forward and install approximately 25 concrete tunnel rings. During this time, they must demonstrate that they have implemented a number of changes to ensure they can safely continue mining."

These changes include:

  • Updated tunnel work and quality plans, including calculations of the amount of soil removed during excavation of each tunnel ring.
  • Realignment of key personnel within their quality assurance program.
  • New quality assurance protocols.
  • New personnel at key positions within the tunneling operation.
  • Restructured daily tunneling meetings that include additional participants and protocols.

WSDOT said it made the decision to conditionally lift the suspension for cause after its team of tunneling experts evaluated documentation submitted by STP over the past several weeks. While mining can resume, barging activities are still restricted pending submittal of additional documentation. STP will remove excavated soil by truck as they continue addressing the barging issue. Repairs to the pier that was damaged during the January 12 barging incident were completed earlier this month.

Work was suspended for cause on January 14 per section 14.2 of the contract, which says the state can suspend work without liability to WSDOT under a number of conditions, including the contractor’s failure to "correct conditions unsafe for the project personnel or general public."

The suspension for cause only addressed tunnelling operations involving the TBM and the loading of barges at the site. It did not apply to the other ongoing work under the design-build contract with STP or any other contracts being managed by the viaduct program.

The conditional lift will remain in place for approximately 160ft (49m) of tunnelling. During this period – which is considered part of STP’s initial testing phase – STP will be operating with additional communication with WSDOT and its tunneling experts. If STP demonstrates that their revised mining procedures are effective, crews will continue mining an additional 100ft (30.5m).

"Seattle Tunnel Partners has addressed the issues that led to the suspension for cause. This conditional lift of the suspension for cause will give STP an opportunity to demonstrate the effectiveness of their updated mining procedures," said acting transportation secretary Roger Millar.

"Above all else, this project has always been about safety. We must continue our work to replace the viaduct, but we have an obligation to ensure that work proceeds safely. We will continue to work with STP while taking whatever steps are necessary to protect the interests of the public moving forward," he said.

As of early March the TBM mining the SR 99 replacement tunnel, has bored approximately 110ft (33.5m) since Seattle Tunnel Partners resumed mining on February 23. The machine has tunnelled a total of 1,391ft (424m).

WSDOT said, "STP is now 17 concrete rings into the 25-ring demonstration period that was put in place when WSDOT conditionally lifted the January 14 suspension for cause. Crews are mining north to a planned maintenance stop just south of Yesler Way. Once there, they could spend several weeks performing final maintenance before the machine tunnels beneath the Alaskan Way Viaduct."