Alaskan Way Viaduct Replacement Tunnel Progresses
The Washington State Dept. of Transportation has qualified four design-build teams that will vie for a $1-billion contract to construct a deep-bore tunnel replacing the seismically unsound Alaskan Way viaduct in Seattle. The winner will begin work on the four-lane, 2-mile-long double-decker tunnel on state Route 99 after the award in late 2010.
WSDOT announced the qualified joint-venture teams: Seattle Tunnel Partners, which includes Dragados USA Inc., Coral Gables, Fla., and HNTB Corp., Kansas City, Mo.; Seattle Tunneling Group, which includes S.A. Healy Co., Lombard, Ill., FCC Construction S.A., Madrid, Parsons Transportation Group Inc., Washington, D.C., and Halcrow Inc., New York City; VTS Joint Venture, which includes Paris-based Vinci Construction, Traylor Bros. Inc., Evansville, Ind., Skanska USA, New York City, and London-based Arup; and AWV Joint Venture, which includes Kiewit Pacific Co., Vancouver, Wash., Germany’s Bilfinger Berger and AECOM Technology Corp., New York City.
The winning team will be required to build a 55-ft wide, 9,000-lin ft tunnel using an Earth Pressure Balance tunnel-boring machine.
The RFP will detail the firms’ plans for completing the five-year project, including the proposed bored tunnel’s design, constructing the tunnel boring machine and building the tunnel, including the interior roadway, tunnel systems, ventilation buildings and portal connections.
Under the design-build contract, the contractor will control the machine specifications. “They have to take into account our very abrasive soils, the production speeds and maintenance requirements,” says Linea Laird, director of Central and North Projects for the replacement program. “We will include some performance criteria.”
WSDOT is giving a $2 million stipend to each team to develop its proposal, except the winner, says Ron Paananen, DOT administrator, Alaskan Way Viaduct and Seawall Replacement Program.
Current local tunneling projects have been rife with difficulties. Sinkholes formed on a separate tunnel built by Obayashi Co., for the Sound Transit Light Rail project. Two TBMs digging on the Brightwater Treatment plant project closed down for maintenance this spring and are still under repair.
“We are watching those very closely,” says Paananen. “The difference here is that our tunnel will only be under 2.5 to 4 ba and ours is larger diameter.” Vinci crews at Brightwater are working under 7 to 8 ba.
The exact tunnel alignment is subject to change. The DOT on Dec. 17 announced plans to change the alignment to avoid buildings in an historic part of Seattle which would be most affected by settling. Tests there also show poor soils, problematic building tiebacks and utility lines that would be affected.
Right now DOT consultants are studying 300 downtown buildings to see if they can withstand settlement. Before tunneling could start, the contract will call for advance mitigation. “It would be up to the contractor to decide the best method,” says Laird.
Though design-build contracts usually place the risk on the contractor, “we don’t expect them to take 100% of the risk. We’d rather have a contract where we can both achieve our goals. We’re really looking for a best value proposal,” says Paananen. “We will also build in a healthy contingency fund.”
The draft RFP is due in early January, says Bill Mariucci, area manager for Kiewit Pacific. “We’ll know more details about what is required then.”
A request for proposal will be developed for the teams by spring of 2010. By the end of 2010, the project will be awarded, says Paananen.
Early this year, the state, county, city, and Port of Seattle recommended replacing the S.R. 99 Alaskan Way Viaduct with a bored tunnel beneath downtown Seattle. The plan includes a new waterfront roadway and public open spaces, transit investments, a new central waterfront seawall and city street improvements.
Environmental review of the proposed bored tunnel is underway, and a supplemental draft environmental impact statement will be available for public comment in 2010.