Proposals called for Seattle's big bore tunnel
Proposals called for Seattle's big bore tunnel May 2010
Shani Wallis, TunnelTalk
With determination to maintain momentum, State officials met deadline this week and issued a request for proposals to build a bored tunnel replacement of the Alaskan Way Viaduct in Seattle. Three international pre-qualified teams now have until October to return proposals ahead of a planned award of contract in January.TBM tunnelling of the 54ft (15-16m) diameter bore could start in 2013 towards a targeted official opening on December 31st, 2015.

Route of the double-deck highway viaduct that is to come down

Released on Wednesday (May 26th), the documents describe the scope of the estimated $1 billion and $1.2 billion project and set technical requirements to be met by the design-build contractors. Much of the strategic and detailed design elements however are left open to the contractors. These include the design, type and manufacture of the TBM; the method and destination of muck disposal; design and manufacture of the segmental lining; and the sequencing of tunnel excavation with construction of the interior road decks. The base design documents prepared by the client's designer Parsons Brinckerhoff and its PMAC (Program Management and Advisory Consultant) Hatch Mott MacDonald includes a geotechnical baseline report (GBR) and specifies pressurised EPB or slurry TBM excavation to cope with ground water pressures up to 5 bar, and control surface settlement above the 9,100ft (2.7km) long large diameter drive some 60ft to 200ft (18-60m) benearth the streets of the city. The RFP also sets out requirements for the highway tunnel's ventilation, fire/life safety, and electrical systems, and construction of its portals.
The three joint ventures prequalified to bid the contract are:
Seattle Tunneling Group (STG) comprising S A Healy; FCC Construccion, SA of Spain;
Parsons Transportation Group; and Halcrow
AWV Joint Venture (KBB) of Kiewit Pacific; Bilfinger Berger of Germany; and AECOM
Seattle Tunnel Partners (STP) comprising Dragados-USA of Spanish parent company; HNTB Corporation

Proposed bored tunnel replacement of the viaducts

A fourth group of Vinci (France)/Traylor/Skanska (VTS) with Arup officially withdrew from the line-up in early April with two partners stating that recent award of other tunnelling projects had influenced their decision. Traylor Bros for example was successful in its $309.2 million bid with Frontier Kemper for the twin running tunnels contract for Seattle's Sound Transit University Link extension between Capitol Hill and the University of Washington, It was also awarded the Queens soft ground tunnels for the East Side Access project in New York City with JV partners Granite and Frontier Kemper. In addition, a senior manager with one of the JV partners told TunnelTalk "it was unlikely we would be considered a front runner given that our lead partner Vinci is battling on the Brightwater project" just north of the Seattle in King County where its two slurry TBMs on the waste water conveyance tunnel have suffered severe wear and the contractor on a different section of the project has been engaged to complete one of the troubled drives.

Viaduct cuts across Seattle's central waterfront

There was also "concern about the scale of the job and the allocation of risk in the contract". These concerns are said to have been addressed by project since the JV pulled out. Representatives of the project met with the design-build teams to review the scope of work and discuss a draft request for proposals released in February. Several changes were made as a result, including adding incentives to meet the December 2015 tunnel opening goal, and adding technical credits in the selection process for the contractors' approach to management, schedule, and settlement mitigation.
Project managers reported disappointment that the VTS JV had withdrawn. Vinci had experience of completing successfully the similar A86 double-deck highway tunnel project in France near Paris in the early 2000s and was leading a JV of strong soft-ground tunnelling experience. They added however that the three other bidders are equally qualified and capable of undertaking the contract.
Approval of the bored tunnel project is subject to the outcome of the final Federal environmental impact statement that is expected in August next year. Advancing the bidding process some 18 months ahead of that provides a year's head start on the project. A substantial amount of work is required ahead of building the tunnel, including demolition of a section of the viaduct to make way for a large open-cut operation to form the southern portal and provide the working access for the proposed south to north TBM drive.
The project is also working against opposition by Seattle's city mayor. Elected last year after strong support of the project by the previous mayor, the new mayor is concerned by the city's exposure to cost overruns. The project includes a mix of lump-sum, unit bid, and shared contingency amounts. Most of the work is to be included in the lump-sum fixed price bid item.

Strengthening vulnerable viaduct supports

State Transportation Secretary Paula Hammond has stated that: "We have structured the majority of the contract as fixed price, which will help meet our goal to deliver the SR 99 bored tunnel within the budget". The estimated $1.96 billion includes design, right of way, construction management, and $415 million set aside for risk and inflation.
The State government, Seattle businesses and most of Seattle's residents are in support of the project and understand that replacement of the damaged viaduct is an urgent public safety concern. Another strong earthquake in this seismically active zone is likely to cause collapse of the damaged viaduct and exact significant loss of life.
In speaking to the press this week Washington State Governor Chris Gregoire said: "It is time to move forward on this critical project and seeking proposals now allows us to take advantage of the best construction bid climate in decades. We have some of the best contractors in the world bidding on this project and I am confident we will end up with a final bid that offers the best value to the taxpayer and a successful, completed project that will keep this vital transportation corridor open for business."
A policy of transparency has been adopted by WSDOT for development of the project. Reports and documents normally kept from public view are freely available on the project's website at These include copies of the RFP documents, the funding arrangements, and the project timeline. TunnelTalk has arranged a visit to the project to prepare a more in-depth report on how this world-class tunnel project will be realised.
Alaskan Way pre-qualifiers and cost review - TunnelTalk, January 2010
Low bid cuts cost of University Link - TunnelTalk, March 2009
East Side Access soft ground tunnels awarded - TunnelTalk, Oct 2009
Brightwater's rescue strategy - TunnelTalk, May 2010

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