The state has narrowed its Alaskan Way Viaduct replacement options down to two: a "surface and transit" plan, and an elevated bypass highway that has two lanes in each direction, running side-by-side.

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The state has whittled its Alaskan Way Viaduct replacement options down to two:

• A “surface and transit” plan that features three southbound lanes on Alaskan Way, and three northbound lanes on Western Avenue.

• An elevated bypass highway that has two lanes in each direction, running side-by-side on independent bridge structures — the cheapest of the highway scenarios, the state says. It would include a Western Avenue exit to Belltown, Seattle Center and Interbay.

The surface-transit option is estimated to cost $3.3 billion, and the elevated version $3.5 billion. That’s higher than earlier estimates because improvements to Interstate 5, local streets and transit have been added.

The figures include about $1.1 billion already budgeted for a Sodo interchange, Battery Street Tunnel safety improvements, and other work to be finished by 2012, before construction at the central waterfront.

The initial announcement today does not say how the project will be funded.

Funding complications

State lawmakers have earmarked only $2.8 billion for the viaduct-replacement budget, funded by state gas taxes and federal bridge grants. More than $1 billion already has been spent or committed for rebuilding the south end of the viaduct and other viaduct-related projects.

The proposed surface plan could add bus routes to Delridge and Lake City, along with trolley and park-and-ride projects, and trip-reduction programs.

But state Transportation Secretary Paula Hammond said the state money can’t be used for increases in Metro bus service that are part of the surface-transit package, because the state constitution requires gas taxes to go toward highways.

“There’s been no decision on, if transit service is part of the package, how that gets paid for,” she said.

A small portion of the $2.8 billion already set aside for viaduct replace comes from car tab taxes, and that money could be used for transit.

Interstate 5 work would include squeezing an additional lane of traffic each way through downtown, as well as rearranging downtown ramps to improve traffic flow, Hammond said.

The state Department of Transportation (DOT) dropped the idea of a bored tunnel for now, but said it could be built later as a “stand alone” project along with the surface-transit option. A bored tunnel is essentially drilled beneath the surface; a cut-and-cover tunnel, which Seattle voters rejected in 2007, involves digging a giant trench and then covering it.

The state calls the two options “hybrids,” because they combine parts of nine proposals studied this year.

The announcement was made today by the DOT, King County and the City of Seattle. Gov. Christine Gregoire said Thursday she plans to make a final choice by Dec. 31. Viaduct projects do not appear eligible for federal stimulus funding being considered by President-elect Obama, Hammond said.

Several top officials and legislative leaders were meeting this afternoon at Seattle City Hall to hear details, which will be presented tonight to the volunteer Stakeholder Advisory Group. A public forum is planned for 5 p.m. Monday at Town Hall in Seattle.

How we got to this point

Leaders and the public have been arguing about a viaduct replacement since at least 2001, when the Nisqually earthquake caused slight sinking, highlighting the vulnerability of what is now a 55-year-old highway.

Representatives from the state, city and county have been working for more than a year to come up with a replacement after Seattle voters in 2007 killed two competing viaduct-replacement plans, a cut-and-cover tunnel and another aerial structure.

The three agencies earlier this year appointed a 29-member “stakeholders” group to evaluate ten competing proposals for everything from traffic, to environmental issues, to economics, to cost.

Over the past month the state said the final choice won’t be one of the eight, but instead would mix the best of each proposal. Last week the Seattle Chamber of Commerce offered its own plan, a combination of a tunnel with improvements to Seattle streets and transit.

Studies show the surface-street alternatives would be the slowest way to get through downtown Seattle. Thursday’s version shows 28 traffic signals and a 30 mph speed limit. An elevated structure would be the fastest with a 50 mph speed limit. That option also a surface street along the waterfront with two lanes in each direction.

Another study found there was little difference in economic impacts among the eight finalists, although businesses along the waterfront could be severely hurt during construction.

A surface plan creates a strip of open space 104 feet wide at the central waterfront. Neither version includes a waterfront streetcar; the city endorses a trolley on First Avenue instead.

Traffic near the Pike Place Market would increase under the surface version. To help offset that problem, the state suggests a one-block northbound underpass for Western Avenue at Virginia Street, next to Victor Steinbrueck Park.

Each finalist has proponents

For months, the viaduct decision has been under intense scrutiny, with special-interest groups carving out their positions.

Environmentalists, particularly the People’s Waterfront Coalition, have been pushing the surface-street plan and the city, realizing its hope for a tunnel would be too expensive, agrees.

Seattle Mayor Greg Nickels said Wednesday that his favorite idea would be a merger of various surface options.

“I continue to think the surface options are the ones to focus on,” he said. Asked if there were any tunnel-surface combinations he liked, he said only that the city is anxious to hear what the DOT presents to stakeholder groups.

It’s questionable whether further room exists for compromise between the remaining two options, given the traffic and engineering differences between an elevated highway and a surface street.

“That gets down to the basic dilemma on this project,” said Ron Paananen, DOT’s viaduct project director.

Many industry officials want the replacement to be another aerial structure so trucks can move quickly from Ballard and Interbay to Sodo and other southern locations.

The Seattle Chamber of Commerce, the Downtown Seattle Association and the King County Labor Council supported a tunnel of some sort that would open up the waterfront.

Tayloe Washburn, board chairman at the Seattle Chamber of Commerce, sounded disappointed by the options discussed Thursday, and said he’d like to consider other alternatives.

“We’re only in the third inning of a nine inning game,” he said. “The conversation will continue.”

The Discovery Institute’s Cascadia Center has pushed for a bored-tunnel option, just inland from the Elliott Bay shore, that would keep the viaduct in place during construction. The highway would reconnect to Aurora Avenue north of downtown. Such a tunnel would be a larger version of those Sound Transit drilled across Beacon Hill this decade.