What can West Seattleites expect if an earthquake takes down the Alaskan Way Viaduct?

The Seattle city police, transportation planners and emergency managers proposed an emergency closure plan for the viaduct to the Transportation Committee of the Seattle City Council July 18. It was a refined version of an earlier, less detailed plan.

Officials from each agency laid out plans for what to do immediately if a midday earthquake forced closure of the Alaskan Way Viaduct.

First, Seattle police officers would block northbound access to the viaduct at Spokane Street.

Closed too would be all of the on-ramps to the viaduct from Spokane Street northward to Denny Way. That would include the on-ramps at First Avenue South by Qwest Field, Columbia Street, Elliott Avenue, Bell Street and Denny Way.

Interstate 5 is planned as the main traffic alternative if the viaduct collapses. High-occupancy vehicle lanes, which normally call for at least two people in a car, could require a minimum of three occupants during the first few weeks of a closure.

Electrical power could be knocked out downtown so most of the traffic signals might not be working. That would slow traffic to a crawl because, during a power outage, people are supposed to treat each intersection as a four-way stop, said Jim Dare of the Seattle Department of Transportation.

To speed things up, emergency managers suggest designating First, Second and Fourth avenues downtown for "unfettered movement north and south" for a temporary period after a quake, Dare said.

While drivers on those north-south streets would have the right of way downtown, stop signs would be in effect on east-west streets. Flaggers would be assigned to some intersections to help control traffic and free police officers for other duties.

Western Avenue or First Avenue could be designated for emergency vehicles traveling north or south. Depending on the specific circumstances and damage from the earthquake, emergency managers would designate James, Cherry or Madison street as an east-west emergency route from downtown to hospitals on First Hill or beyond.

The city has contracted with a private company to provide portable electronic message boards to help alert motorists to problems and route changes.

Without electricity downtown, the waterfront trolleys would be powerless so heavy-duty tow trucks are assigned to push the trains to the trolley barn, if possible.

If there is power to operate traffic signals, the city's Traffic Management Center would switch to its evening-commute computer program, which is designed to move people out of downtown, Dare said.

Closer to West Seattle, discussions have been underway among emergency managers and nearly a dozen shipping companies that ply the Duwamish River and depend on the Spokane Street low-level bridge to open for them.

Each opening and closing of the world's first double-leaf, hydraulic swing bridge can take 10 to 20 minutes. To keep the swing bridge from unnecessarily impeding vehicle traffic in and out of West Seattle, emergency managers have been urging the shipping companies to coordinate their sailing times so that, in case of a viaduct closure, vessels could move through the open bridge in groups. That would reduce the number of bridge openings, which normally stop much of the vehicle traffic on Spokane Street about 10 times a day.

Metro buses make more than 500 trips a day on the Alaskan Way Viaduct. When the Nisqually earthquake occurred and the viaduct was closed, most of those buses switched their runs to First Avenue, said Jim Jacobson, deputy general manager of Metro, in a follow-up interview.

Metro has a "fluid" emergency plan that depends on reacting to the specific problems that an earthquake or other viaduct-closing event would present, he said.

"It depends on whether it would be a change for one week or a four-year thing," Jacobson said.

If need be, buses on lesser-used routes could be diverted to downtown to help move people. However, if West Seattle was disproportionately affected by closure of the Alaskan Way Viaduct, Metro would probably keep all of its West Seattle buses running, he said.

A woman who spoke during the public comment portion of the meeting said she lived in Los Angeles during the Northridge earthquake. Freight-hauling trucks were given priority on the freeways during specific hours of the late night, she said.

Planners recommend to truckers which streets can best accommodate large trucks, but truckers are legally free to drive wherever they want. The city might temporarily divert trucks longer than 30 feet from entering downtown if an earthquake brought down some or all of the Alaskan Way Viaduct.

There was some grief expressed by citizens at the meeting about possible parking restrictions on First, Second or Fourth avenues. That would hurt businesses along those streets, they said.

Another citizen suggested setting up temporary parking lots.

City Councilman Richard Conlin suggested moving more freight by barge if the viaduct were closed in an emergency. But his colleague, Councilman Richard McIver, cautioned that marine facilities might also be damaged due to liquefaction in an earthquake. But McIver also recommended having more water taxis.

Tim St. Clair can be contacted at 932-0300 or tstclair@robinsonnews.com