June 29, 2001

Engineers say scrap Alaskan Way viaduct

SEATTLE (AP) -- The Alaskan Way viaduct that carries Washington 99 along the downtown waterfront should be replaced within a decade rather than quake-proofed, an engineering team has advised.

That assessment is being released Thursday by the Alaska Way Viaduct Structural Sufficiency Team, six independent engineers hired by the state to weigh three options -- repairing, retrofitting and replacing the earthquake-damaged span.

As of five years ago, a University of Washington study estimated retrofitting would cost $340 million, a teardown about $120 million and replacement about $530 million. Costs would likely be higher today.

"Even though a comprehensive seismic retrofit might achieve a level of safety comparable to a new structure," the engineers wrote, "the eventual deterioration of the current structure due to aging would exact a greater sum of financial resources for maintenance and be less reliable than a new structure built to current seismic design standards."

The 48-year-old elevated roadway links downtown with the Duwamish industrial area, running between the Battery Street tunnel south of the Space Needle to the Spokane Street viaduct south of Safeco Field.

The engineering team, headed by David Goodyear of Olympia, was hired after the 6-8-magnitude Nisqually quake on Feb. 28 left cracks in the 48-year-old span and caused it to tilt 3 inches eastward at South Washington Street in Pioneer Square.

The double-deck span normally carries 100,000 cars a day, one-third of the city's north-south traffic, but is now restricted to two lanes in each direction and is closed to northbound trucks and buses. There have also been intermittent closures of the entire viaduct since the quake.

A $5 million study that is set to begin this fall includes an environmental review of four options -- retrofitting, building a new viaduct, replacing the viaduct with a tunnel and a simple teardown.

The report estimated there is a 1-in-20 chance of the viaduct would collapse in a future quake.

"That risk is greater than acceptable," state Transportation Department spokeswoman Linda Mullen said Wednesday. "We have to act now."

Replacing the 2.2-mile viaduct will take about 10 years, the same amount of time required to strengthen it to withstand earthquakes, the report said.

"Clearly, we need to move quickly," Mayor Paul Schell said Wednesday night. "This is not a risk we can afford."

Retrofitting remains an option, Mullen said.

In any event, the viaduct should be put at the top of the list of state transportation priorities, said Aubrey Davis, a member of the state Transportation Commission.

"We can't wait," Davis said. "If replacement is the only option we have, we have to start right away. We can't wait until it falls down."

Tear it down before it falls on people. Remember the Nimits freeway in Oakland? One more good earthquake up here, and hopefully no one is around the viaduct- is that likely to happen?

You got: tear it down, retrofit it, or replace it with a tunnel. My idea is to replace it with a new and improved, up-to-date, and fully retrofitted with today's standards. Also add some style to it so that it could blend in with it's natural surroundings. For example, if a new viaduct replaced the existing one using Safeco Field-type steel and metal, it would look sharp.