The day after the Nisqually earthquake, commuters got an early glimpse of life without the Alaskan Way Viaduct. With the elevated highway barricaded for a safety inspection, North...

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The day after the Nisqually earthquake, commuters got an early glimpse of life without the Alaskan Way Viaduct. With the elevated highway barricaded for a safety inspection, North End traffic extended to the Snohomish County line, while a trip from West Seattle to downtown took two hours.

What would happen if nature caused another shutdown?

Nearly four years after the shaking on Feb. 28, 2001, transportation agencies have produced only a draft of an emergency detour plan. City officials admit it’s not aggressive enough to keep Seattle mobile.

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Last week, the City Council passed a resolution calling for a stronger version by February. And Wednesday, a lengthy traffic jam caused by a blocking collision on the viaduct dramatized the need for detours.

The current plan, put together by the Washington State Department of Transportation, would shift South End viaduct traffic to First Avenue South. The route would skirt downtown along Alaskan Way, the waterfront surface street that crosses railroad tracks twice and has only one northbound lane near the ferry terminal. The route would continues through intersections in the Mercer corridor, already prone to stop-and-go traffic.

If the waterfront street also were closed by leaks in the seawall or by viaduct debris, a last resort would employ Second Avenue and Fourth Avenue through downtown.

“None of these arterial routes can be viewed as a serious substitute for the expressway capacities the AWV [the viaduct] currently provides,” says the plan itself.

It contains other ideas such as extra turn lanes, timing of traffic signals, park-and-ride shuttles and a massive public shift to transit. But funding and details haven’t been worked out.

“I don’t really know why. But I’m upset about that fact,” said City Councilman Richard Conlin, who heads the council’s transportation committee. “I didn’t really focus on it. I assumed they had taken care of it, once they had the [Nisqually] earthquake.”

Patrice Gillespie-Smith, chief of staff for the Seattle Department of Transportation, acknowledged that detour preparations lagged this year as the city concentrated on finishing its environmental-impact statement for a proposed $4.1 billion, partly tunneled replacement for the 51-year-old viaduct.

There’s no easy solution because of the city’s narrow, hourglass shape, said Maureen Sullivan, a state project manager. Interstate 5, the only other highway through downtown, is nearly full to capacity already.

Detour planning is more than a tabletop exercise.

State engineers have laid odds of 1-in-20 that an earthquake will disable the viaduct in the next several years.

Its weakest support pier, near the ferry terminal, has sunk 4 inches since the Nisqually quake. An additional 2-inch drop would force buses and trucks off the viaduct, explained Tom Madden, engineering manager for the viaduct replacement.

Though officials hope to break ground on the tunnel by 2009, there’s no assurance federal, state or local taxes will be available for the project by then. With each passing year, emergency detours seem more plausible.

Sullivan said the state will is learning more as traffic studies are done for the future tunnel. The detour plan will always evolve, and a final response would depend on the nature of the quake, she said. “You would have to tailor it and make your adjustments anyway.”

West Seattle headaches

If an earthquake strikes tomorrow, authorities have procedures to immediately open an emergency-operations center. The city says it can set up detour signs within four hours.

Katherine Casseday, the city’s chief traffic engineer, can order parking bans and lane changes.

While the state plan provides a north-south detour, it doesn’t address how to handle traffic spilling from the West Seattle Bridge, which at 107,600 daily trips is slightly busier than the viaduct.

“This is the most doomed area of transportation I’ve ever seen,” said commuter Jessica Olson, sitting in the Metro 55 bus Wednesday morning. It had left the West Seattle Junction at 7:35 a.m. and reached the Pike Place Market around 8:25. The driver took First Avenue South, already occupied by commuters from the airport-area suburbs.

“We need reliable surface streets, at least one more surface street that won’t be compromised,” said Olson, a legal assistant. Fourth Avenue South and Airport Way South should be part of the plan, said rider Ilana Kennedy.

Other options

While the state plan suggests limiting turns on First Avenue South, it doesn’t call for using other boulevards in Sodo, the area south of downtown near Safeco and Qwest fields. Madden said that there is some room to absorb more traffic but that downtown streets are now about 85 percent full.

While the current plan serves the state’s needs by maintaining a highway detour, it doesn’t keep the city’s street grid flowing, said Gillespie-Smith. “We need to add procedures that will free up more lanes and add capacity on the arterials,” she said.

More options are getting a look:

• Parking bans along detour streets.

• Shifting some traffic from southbound Aurora Avenue onto Dexter Avenue North, though that means more cars whizzing along a productive bicycle route.

• Adding an exit lane from Aurora to Denny Way, maybe for buses only.

• A ramp from Qwest Field to Airport Way South, which Madden said could provide another outlet from downtown.

• A second pedestrian overpass at the waterfront to protect people from the detouring traffic.

City Councilman Tom Rasmussen favors the plan but wants a driver-notification system, using radio stations, signboards and neighborhood-business marquees along California Avenue Southwest.

He said the city should improve readiness not only for an earthquake but for serious traffic tie-ups like that on Wednesday, when he was stuck behind the wheel for 40 minutes

“We really need to have a better plan to deal with emergency closures like this, because it was pretty much every driver for themselves,” he said.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com