SEATTLE (AP) – The Alaskan Way Viaduct is an economic lifeline for this car-dependent city, its twin concrete decks soaring above the famously sparkling waterfront to shuttle more than 100,000 automobiles each day.

It is also drab, rickety and outdated. And Mayor Greg Nickels wants nothing more than to bury it underground.

But as Nickels and his allies push for a major new tunnel to replace the roadway, some critics are pointing to Boston, where another ambitious bid to transform the face of a city stampeded past deadlines and cost estimates.

“The Big Dig is the nightmare that we all have here in Seattle,” said Nick Licata, the City Council president and a vocal critic of Nickels’ plans.

Supporters dismiss such dire predictions, and are confident that a proposed citywide vote this fall could give them a crucial stamp of public approval.

“Some cities make the right choice and some make the wrong choice,” Deputy Mayor Tim Ceis said. “We made the wrong one in the ’50s, and now we’ve got a chance to fix it.”

In broad terms, Seattle’s viaduct shares common elements with the Big Dig: Both involve coastal cities, hungry to reclaim the views and property values that were scarred by their Cold War-era elevated highways. The comparison breaks down in the details.

The Big Dig created a series of tunnels to replace Boston’s old Central Artery. At $14.6 billion, it is the most expensive highway project in U.S. history.

It’s been considered an engineering marvel, but also has been plagued by cost overruns, delays and faulty construction that culminated in one motorist’s death under a collapsed tunnel ceiling in July.

Nickels’ plan for Seattle is more modest, consisting of a single tunnel topped by a sweeping new urban park and commercial zone.

State Transportation Secretary Doug MacDonald, who formerly served as director of the Massachusetts Water Resource Authority, said the Big Dig comparison is not entirely apt. But one can expect to see Boston’s troubles referenced whenever officials publicly battle over a major project, he said.

“The Big Dig now has become almost a mythical thing in the American public works landscape, for good and for ill,” MacDonald said. “I don’t think simply labeling something as the next Big Dig teaches you very much.”

But the label still fits, Licata said, as shorthand for insufficient forethought amid the excitement of remaking a city.

“The determination to see it done blinded one to the public safety hazards that would result if you don’t spend enough money,” he said.

The present viaduct definitely is a liability. Built in the 1950s, it was damaged in a 6.8-magnitude 2001 earthquake. Engineers warn that another temblor from the faults crisscrossing this area could collapse its towering decks.

Standing in a parking lot beneath the viaduct recently, Dan Wolters, 50, of Missoula, Mont., said the hulking highway recalls the double-decker Bay Bridge, which partially collapsed during the 1989 Loma Prieta earthquake in San Francisco.

“If you guys have an earthquake here, it’d go shhhhhmuck!” Wolters said, slapping his hands together as if squashing a mosquito.

Two replacement options have emerged as serious contenders: Nickels’ tunnel, and a competing proposal to build a new elevated highway.

Depending on the size of each, an elevated highway could cost between $2 billion and $3.1 billion; a tunnel could cost from $3 billion to $4.5 billion, the state says.

Two cheaper alternatives also have been discussed.

The People’s Waterfront Coalition argues against replacing the viaduct at all, instead relying on public transit and urban planning changes to disperse the traffic.

State and city officials, however, have said that plan doesn’t realistically handle the traffic that now flows over the viaduct, up to a quarter of the north-south travel in Seattle.

The second alternative would brace the viaduct with beams and other devices. Prominent engineers have endorsed this approach, which is far less costly and could keep traffic flowing during construction.

That contrasts with the two leading options, which would disrupt traffic for several years in Seattle. But officials have said the retrofitting plans would not do enough to strengthen the existing viaduct in a major earthquake.

Veteran engineers behind the proposal, including Jack Christiansen of Bainbridge Island, grumble they’ve been shrugged off by government leaders.

“I don’t know exactly why that is, except maybe people don’t like to listen to old guys,” he said. “And maybe they just simply want to do a big, new project.”

There is about $2.4 billion committed for the viaduct project, but some key legislators have warned Nickels that his tunnel plan is a nonstarter. In a letter to experts evaluating the plans, state House Speaker Frank Chopp, a Seattle Democrat, and two other influential state lawmakers made their views clear.

“The Legislature funded a rebuild, not a tunnel,” they wrote. “Almost all of the (tunnel’s) proposed funding sources are future possibilities, some years ahead. We believe they are too risky to count on.”

Nickels’ administration downplays such criticism, saying they have accounted for inflation and difficulties in attracting enough money from Congress or other sources. Instead, city leaders seem certain their vision for a once-in-a-generation waterfront overhaul will carry the plan to victory.

“Yes, it costs more money,” said Ceis, the deputy mayor. “But it’s worth it.”

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On the Net:

State DOT: http://www.wsdot.wa.gov/Projects/Viaduct

Nickels’ viaduct plans: http://www.seattle.gov/mayor/issues/viaduct/

AP-ES-08-20-06 1332EDT