Transportation department set to sign $1.1B tunnel contract

The state Department of Transportation (DOT) says it's ready to sign a $1.1 billion contract Thursday for construction of its proposed Highway 99 tunnel.

The four-lane passage from Sodo to South Lake Union would be drilled by a 58-foot-wide boring machine — the world's widest — through glacial soils that are mostly stable, but abrasive and laced with groundwater and small boulders.

Excavation could start in late summer followed by drilling in 2013, assuming the project wins federal approval for its environmental-impact statement.

The contractor Seattle Tunnel Partners, led by Dragados USA and Tutor-Perini, offered the best proposal in a two-team competition for the project, state managers said.

The competitors offered nearly equal dollar prices, but the winning group promised 2 feet more road width and a sooner completion date of Dec. 31, 2015. The team includes local builders Frank Coluccio Construction and Mowat Construction, and the Bellevue branch of design firm HNTB.

Signing ceremonies are planned for 3 p.m. Thursday at the Port of Seattle headquarters, Pier 69, DOT spokeswoman Kristy Van Ness said. The companies have spent the past few weeks submitting insurance documents and other paperwork.

Besides the $1.1 billion basic price, the team would receive $210 million in stipends to cover inflation and insurance costs. After those costs, plus incentive bonuses, and the state's own engineering and management costs, the tunnel project has about $100 million left to cover unknown risks.

Tunnel critics, including Seattle Mayor Mike McGinn, have argued Seattle taxpayers aren't protected in case of cost overruns. Also, the state hasn't figured out yet how to collect about $400 million in tolls needed to help pay for the project.

Meanwhile, anti-tunnel Initiative 102 is scheduled to launch its signature drive Jan. 12, said co-organizer Drew Paxton, who favors a nonhighway alternative using transit, surface streets and improvement to Interstate 5. The measure would order the city to obtain "a viable and transparent funding plan" for the tunnel before signing any tunnel agreements with DOT.

A separate initiative, I-101, which seeks to ban outright the use of city right of way for a tunnel, is closing in on the needed 20,629 valid signatures for a possible May ballot measure.

State lawmakers in 2009 designated a tunnel as part of a broader $3.1 billion replacement for the Alaskan Way Viaduct.

Mike Lindblom: 206-515-5631