It's no secret that the state needs to replace the Alaskan Way Viaduct, a tottering waterfront highway that was damaged in the Nisqually earthquake exactly five years ago. State engineers say the viaduct stands a 1-in-20 chance of failing in the next 10 years, potentially toppling on its side and killing and injuring hundreds.

It's also no secret that Mayor Greg Nickels and the Washington State Department of Transportation (WSDOT) favor replacing the viaduct with a tunnel, "opening up the waterfront" to parks, condos, and new commercial development. According to Nickels, building the tunnel "gives us the chance to transform the front door of our city into a spectacular public gathering place for generations to come." At a press conference on a wet Monday morning just over a year ago, Nickels—wearing a bright-green button bearing the motto "The Tunnel—Dig It!"—vowed to "make our waterfront a cleaner, quieter, more beautiful place for all."

However, the reality of the tunnel is much different from the vision Seattle is being sold. Instead of what most people probably imagine—an underground structure extending the length of the waterfront, hidden from view by landscaping, parks, and new commercial development—the mayor's tunnel plan also includes a new elevated viaduct and a six-lane surface highway. On the north end, six lanes of traffic would roar out of the ground at Pine Street, heading onto a new bridge wider than the current Alaskan Way Viaduct at exactly the point where Pike Place Market meets Victor Steinbrueck Park. Motorcycles, trucks, and cars would have to accelerate sharply to make it up the tunnel's steep 7 percent grade, causing a racket and belching pollution into the north end of the market.

At King Street, on the south end of the tunnel, the story is much the same. There, the tunnel would terminate into a six-lane surface highway—a 180-foot-wide river of traffic that would permanently sever south Pioneer Square and the stadium district from the waterfront.

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What happened to the beautiful, serene waterfront Nickels promised? The simple answer is, he couldn't come up with the money. The state transportation tax passed by the legislature in 2005 will only provide about $2 billion; the federal government has kicked in just $226 million, and U.S. Senator Patty Murray, the highest-ranking Democrat on the U.S. Senate Transportation Appropriations Subcommittee, called Nickels's proposal a "pie in the sky" plan.

As a result, Nickels's tunnel has been cut back to two-thirds of its original 20-block length. Under the initial proposal, the tunnel would have extended from Pioneer Square to Belltown, where it would have linked to the existing Battery Street Tunnel. (This is the tunnel project most people assume the mayor is talking about.) But public outcry over the tunnel's high price tag and a shortage of financial support from the feds forced viaduct planners to cut costs, resulting in a dramatically scaled-back proposal. The changes saved money (the latest estimate is as little as $3 billion, down from a high of nearly $12 billion in June 2002), but at a high cost to some of Seattle's historic treasures. Besides cutting off Pioneer Square and dumping noise and air pollution into Pike Place Market, the new plan eliminates the north end of the seawall and does not reconnect the street grid over Aurora Avenue, two parts of the initial proposal Nickels once characterized as critical.

To listen to Nickels talk now, though, you might think the plan hadn't changed at all. In fact, Team Nickels is talking as though the viaduct will still be everything he initially promised—despite $9 billion in cuts and the elimination of many critical features from the original plan. "People should start believing us. We're going to get there," Deputy Mayor Tim Ceis told the Seattle Times last December.

The likelihood of squeezing more money out of already tapped state and federal resources is low. Existing funds plus "anticipated" funds for the viaduct only cover $3.2 billion of the cost—not enough to replace it with another viaduct, barely enough to finish Nickels's latest, bare-bones "core" proposal, and more than a billion dollars short of the truncated tunnel. And if the viaduct tunnel goes over budget, taxpayers will be on the hook for the overruns.

And don't expect Nickels's estimates to be on target. On-budget infrastructure projects are the exception, not the rule; worldwide, according to one Danish study, 9 out of 10 megaprojects go over budget. In the U.S., megaprojects average cost overruns of 40 percent. The so-called Big Dig, a notorious waterfront cut-and-cover tunnel in Boston, went over budget by 275 percent and still needs repairs. Nonetheless, despite overwhelming evidence that megaproject costs are almost universally lowballed, Nickels and the state insist their numbers are solid. "Our analysis gives a 90 percent probability that the tunnel can be built for $4.5 billion," the high end of the current range, Ron Paananen, WSDOT's Viaduct Project Manager, says. "I'm fairly confident that we have reasonable numbers."

One tunnel skeptic, City Council Member Peter Steinbrueck, calls the mayor's numbers "seriously suspect. The numbers have not been adequately updated since they came up with them two years ago." Since then, construction and building material costs have spiked dramatically. "All we have to do is look at the monorail," which was $200 million over budget when voters scrapped it last year, "to see what happens with megaprojects."

As The Stranger has written countless times, there is another, more sensible option: Replace the viaduct with a waterfront boulevard, give people incentives to get out of their cars, and make improvements to surface streets downtown, redistributing traffic throughout the street grid. This "no-highway option" is being pushed by the People's Waterfront Coalition, a group of transportation activists, including vocal landscape architect Cary Moon. But whether the city ultimately buys into the no-rebuild option (momentum, though building, is minimal), there are plenty of better uses for $4 billion (improvements to I-5; bridge replacements) than a tunnel that cuts off Pioneer Square and hurts Pike Place Market.

As for complaints that closing the viaduct will result in traffic nightmares from Everett to Tacoma: The state already plans to shut down the viaduct during construction—at least partially, under the longest (10-year) construction scenario, or completely, under the shortest (7-year) timeline. In a recent study, WSDOT found that closing the viaduct during construction could save it $300 million to $500 million, but would add 25,000 cars to I-5 daily. Moon disputes that number, noting that it is based on two-year-old information that assumes drivers will not change their habits. Numerous studies have shown that increased traffic leads to changes in commuter behavior; drivers switch to other modes of transportation, such as transit, combine trips, or delay some trips altogether. If we can live without the viaduct for four years or longer, a scenario that now appears increasingly likely, why can't we shut it down permanently?

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Victor Steinbrueck Park, named for Peter Steinbrueck's father, a prominent architect who led the fight to save Pike Place Market from demolition in the 1960s, is a 0.6-acre patch of grass that borders the north end of the market and offers a nearly panoramic view of Mount Rainier, the Olympic Mountains, and Elliott Bay. In the summer, the sidewalk leading to the park bustles with street vendors under bright umbrellas; on warm days, the park is filled with picnickers and downtown office workers. It's noisy in the way that cities are noisy: The viaduct is audible far below, but you can have an ordinary conversation without raising your voice.

If the mayor gets his way, though, the tunnel will obliterate all this. Six lanes of traffic will run parallel to the park, belching pollution and noise into the vendors' stalls and destroying the park's ambiance. Civic activism in Seattle, it seems, has come full circle. Thirty-five years ago, activists like Steinbrueck fought to save the market from redevelopment. As details about the mayor's plan emerge, it seems increasingly likely that Steinbrueck and other Nickels antagonists on the council will have to fight to save Pike Place Market yet again.