"Hybrid" plans combine tunnel, surface streets in place of viaduct

As the team putting together a plan for replacing the Alaskan Way Viaduct completes its work this month, so-called "hybrid" options are surfacing.

The latest, presented Monday night to the viaduct citizens group known as the stakeholders, was put forth by Tayloe Washburn, board chairman at the Seattle Chamber of Commerce. He calls it a "surface-subsurface hybrid."

Washburn's idea is to put the viaduct traffic in a tunnel, either a deep-bore tunnel or a lidded trench. Both are among eight options being studied for viaduct replacement. But Washburn's plan also would:

• Extend the proposed trench so it would be as long as the proposed bored tunnel, which would run from South Royal Brougham Way, near Safeco Field, to Harrison Street, near Seattle Center. Under the present working scenario, the trench would go only from Union Street to Yesler Way.

• Put two, or maybe three, traffic lanes atop the trench, instead of four.

• Consider regional tolling to pay for the new viaduct.

• Consider alternative tunnel designs, such as three levels, one dedicated to freight trucks and transit.

• Consider separating the seawall replacement from the rest of the project, and stage work in phases when cruise ships and tourists are not on the waterfront.

Washburn also suggested improvements to Interstate 5 and better use of city streets.

Eight options now are being considered for replacing the viaduct: three surface-street proposals, two elevated and three tunnels.

The state, the city and King County plan to narrow the choices to two or three on Thursday and present them to the governor, who, with the city and county, will make a decision by the end of the year.

Susan Gilmore: 206-464-2054 or sgilmore@seattletimes.com