A second transit tunnel under downtown Seattle could cost as much as $1 billion and take at least eight years to complete, a preliminary report for the state Department of Transportation says.
That means it probably doesn't make sense as a way to get Sound Transit's proposed light-rail line through downtown, business leaders who pushed for the study concede.
"It's not an affordable option in the short term," said Steve Leahy, president of the Greater Seattle Chamber of Commerce. "There were some of us who were hoping it would be more affordable."
But a second tunnel may have merit down the road — perhaps for buses or another light-rail line, he and others added.
King County Executive Ron Sims, who also is Sound Transit's board chairman, said the new report provided no reason for the agency to reconsider its plan to run light-rail trains through the existing Metro downtown bus tunnel under Third Avenue.
"But it gives us an idea for what we might want to do someday, off in the future," Sims said.
The chamber of commerce and Downtown Seattle Association began pushing for a study of a new tunnel last fall, after Sound Transit, beset by cost overruns, scaled back its proposed light-rail project to a 14-mile, $2.1 billion line linking downtown with Tukwila.
The agency said the shorter route would attract just one-third as many riders as the original line it had planned to build between SeaTac and Seattle's University District.
Sound Transit said its new plan would allow some buses to remain in the Metro tunnel (the agency's original plan had called for the tunnel to become all-rail). But the downtown business groups argued the new "joint operations" plan would result in no significant increase in the number of transit patrons using the tunnel and do little to ease downtown congestion.
A second tunnel for light rail could allow more bus service in the existing tunnel rather than less, some said, and might eliminate possible conflicts between buses and trains.
Sound Transit agreed to cooperate with a study of a second tunnel if someone else took the lead. The state Department of Transportation came up with about $125,000 for a preliminary investigation and hired Bellevue consulting firm HNTB, which hosted a three-day technical workshop that included national experts on tunnel construction.
The consultants' 24-page report was distributed to business and government officials at a briefing Tuesday. It identifies a 1.8-mile route for the second tunnel along Fifth Avenue, with stations at either end adjacent to and connecting with the existing tunnel's International District and Convention Place stations.
It proposes a third station in the heart of downtown's office district, under Fifth Avenue between Cherry and Marion streets. The second tunnel would pass under the Metro tunnel's Westlake station, but would not have its own station there or connect with the existing one.
Permitting, engineering and construction could take eight to nine and a half years, the report says. Because Sound Transit now plans to open its light-rail line in 2009, switching to the second tunnel would delay the project.
The report says the second tunnel could cost between $540 million and $800 million in today's dollars, depending on such variables as soil conditions, real-estate prices and environmental restrictions.
But when inflation is taken into account, it says, the second tunnel's costs could zoom to between $660 million and $980 million in 2008, considered the likely midpoint for construction.
" 'Where's the money?' would be the question that lurks," said the chamber's Leahy.
The Metro bus tunnel, which opened in 1990, cost $455 million. Sound Transit plans to spend $68 million converting it to joint bus-rail operations starting in 2007.
Sound Transit Executive Director Joni Earl said her agency never considered the second tunnel as a serious alternative. The cost estimates and long construction schedule spelled out in the new report "probably put it to rest for the short term," she said.
Downtown Seattle Association President Kate Joncas said she hasn't had a chance to discuss the report with her board. But Leahy's assessment that the second tunnel is too expensive for Sound Transit now "might be a rational conclusion," she said.
However, Joncas said, the report confirms a second tunnel is feasible, "and that certainly does raise some intriguing questions" for the long term.
The second tunnel could be built for buses, she said: Sound Transit and Metro plan to phase them out of the existing tunnel as light-rail service expands, probably no sooner than 2016.
Or the second tunnel could handle a light-rail line from the Eastside if one were built, Sims said.
Eric Pryne can be reached at 206- 464-2231 or email@example.com.