Seattle Tunnel Partners has confirmed that disassembly of the SR 99 tunneling machine is complete, and assessment of the damage is ongoing. They will not provide a revised schedule for resuming mining until they fully understand the scope of repairs.STP has indicated that they will replace the main bearing and outer seals of the machine as expected. They have also decided to replace the inner seals to make them more compatible with the new outer seals and easier to access should the need arise. The new inner seals were designed and manufactured in Japan and are scheduled to arrive in late May.Damage to the machine was more extensive in some areas than anticipated and some minor damage occurred during disassembly. For example, the outer seals and the steel retainers that hold them in place were destroyed. There was also damage to the cutter drive motor pinions and the main bearing bull gear.As owner of the tunneling machine, STP and Hitachi are responsible for all aspects of the repair effort. We will continue to provide updates as we receive them.Reports say natural influences, dewatering caused ground settlement near tunnel access pitSettlement levels remain steady six months after initial detectionAfter months of study, experts agree: there are no simple answers regarding what caused the ground near the SR 99 tunnel access pit to settle approximately an inch last November.Settlement near the pit and in the surrounding neighborhood was caused by a combination of historic and ongoing natural ground movement in the region, dewatering related to tunneling machine repair work and dewatering related to other construction in the area, according to two reports released Monday by the Washington State Department of Transportation.One report, conducted by geotechnical firm Shannon & Wilson, Inc. and commissioned by WSDOT, concluded that dewatering related to tunneling machine repairs was the primary cause of the settlement. A second report , conducted by Brierley Associates and commissioned by tunnel contractor Seattle Tunnel Partners, concluded that natural settlement and other dewatering activities are the primary reasons for the settlement, and tunnel-related dewatering only contributed in areas immediately surrounding the pit. Both reports relied on the same data points.The issue began late last year, when the tunnel project’s monitoring system detected settlement in the vicinity of the 120-foot-deep pit STP built to access and repair the tunneling machine. In response to the settlement, WSDOT and STP increased the frequency of monitoring – which includes hundreds of instruments near the access pit – and assessed the viaduct and nearby buildings.Both reports demonstrate that settlement related to dewatering has since stabilized; they also agree the ground movement was minor and caused no structural damage. The Shannon & Wilson report, utilizing in part information from satellites, also identifies settlement in areas surrounding the project – in some cases, outside the ongoing monitoring area. Though satellite imagery is helpful to indicate trends, ground monitoring is the most reliable gauge of ground activity, which is why WSDOT’s monitoring program relies mostly on ground sensors throughout the project area.WSDOT and STP are continually evaluating ground conditions and taking proactive steps when needed to prevent further project-related settlement. That includes reviewing existing procedures for reducing dewatering should it become necessary. WSDOT has asked STP and city officials to work with project staff to further analyze the data and conclusions in the two reports to find consensus. The agency is also increasing monitoring in some areas and expanding the overall monitoring program in keeping with the analysis provided in the reports.Alaskan Way Viaduct Replacement Program Administrator Todd Trepanier made the following statement regarding the reports:“We all agree that public safety and protecting infrastructure are our top priorities. This is an incredibly complex issue, but all of us – the state, our contractor, the city – have a shared interest in reaching consensus and acting in the interest of public safety. Having reliable information is essential to any decision-making process. These studies will help inform future decisions about construction as we work to replace the viaduct.”— more —
This week, the three-member board appointed by WSDOT and Seattle Tunnel Partners (STP) to assist in resolving contractual disputes issued its latest recommendation. The question before the board was narrow in scope: Was an eight-inch steel well-casing within the work zone adequately identified in the contract? The board determined that the well casing was clearly identified in contract documents, but that the contract documents did not clearly identify that the casing was made of steel.The Dispute Review Board recommendation states: “This recommendation is not to be considered as providing any information or merit related to the question of any impacts or cost that might have resulted from this obstruction. This recommendation only addresses the specific question of whether or not the eight-inch steel casing is a differing site condition under the contract.”Recommendations made by the board are not legally binding; they are simply one step in a prescriptive process designed to aid WSDOT and STP in resolving contractual disagreements. In addition to saying nothing about what damaged the tunneling machine, the recommendation does not assign any cost related to this issue.Alaskan Way Viaduct Replacement Program Administrator Todd Trepanier made the following statement:“It’s important to emphasize the specific question before the Dispute Review Board was narrow in scope and only addressed one issue: whether an existing eight-inch steel well-casing is a ‘differing site condition’ under the terms of the SR 99 tunnel contract. The hearing and subsequent recommendation did not deal with how the tunneling machine was damaged or the costs associated with repairs. The process of resolving disputes can be complicated and must follow the contract. WSDOT disagrees with the recommendation and does not consider this issue to be resolved. We are concerned with the reasoning used by the Dispute Review Board in reaching the recommendation. We are reviewing it and will continue to pursue the best interests of taxpayers as we determine the appropriate next steps.”Seattle Tunnel Partners Project Manager Chris Dixon made the following statement:“Seattle Tunnel Partners position was that the presence of the eight-inch diameter steel casing constituted a differing site condition under our contract with WSDOT. The Dispute Review Board’s recommendation supports and upholds Seattle Tunnel Partners’ position and represents one step in the prescribed process for resolving disputes under the contract. Seattle Tunnel Partners agrees with the recommendation. Seattle Tunnel Partners has advised WSDOT that Seattle Tunnel Partners has accepted the recommendation and considers this issue to be resolved.”— more —
It’s been a busy week since Seattle Tunnel Partners lifted the SR 99 tunneling machine’s front end to the surface for repairs. Crews spent the first few days after the lift cleaning and disconnecting parts. Then, on Friday afternoon, they removed the machine’s bearing block and set it on a platform south of the cutterhead.Further disassembly will continue in the coming days, including removal of the main bearing. When the disassembly phase of STP’s repair effort is complete, manufacturer Hitachi Zosen will begin making repairs and enhancements (links to YouTube). You can continue to track STP’s work on our time-lapse cameras and follow @BerthaDigsSR99 on Twitter for updates. Don't forget to check out the other resources we've created to give you a fuller understanding of Bertha's story:
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- Three-angle time-lapse video of Bertha's front end lift (links to YouTube)
- Single-angle time-lapse video of Bertha's front end lift (links to YouTube)
- Time-lapse video of Bertha's first piece rising to the surface (links to YouTube)
- Time-lapse video of Bertha parking in the pit (links to YouTube)
- Video of Bertha's breakthrough (links to YouTube)
- Video of crews chipping a Bertha-sized circle on the face of the pit’s southern wall (links to YouTube).
- Narrated video explaining STP's repair plan (links to YouTube)
- Seattle Tunnel Partners repair work plan (pdf 4.8 Mb)
Crews working for Seattle Tunnel Partners have reached a concrete milestone at the SR 99 tunnel’s south portal.
As shown in the aerial photo below, crews are building the cut-and-cover section of the tunnel in SODO, just west of Seattle’s stadiums. Earlier this month, they successfully poured the final sections of northbound mainline roadway concrete for this 1,500-foot-long stretch of the future highway.
Sections of cut-and-cover tunnel at both portals will … more