SEATTLE » This city’s urban shoreline on Puget Sound was never built with photo-snapping tourists in mind, or technology entrepreneurs jogging in the rain. In decades past, stretching back to the big-timber-and-fish era of the 1800s, the waterfront was a place of gaff hooks, warehouses and stink.

But as brawny old Seattle faded, the hard parts of its industrial past — a shadow-casting highway viaduct, a crumbling sea wall — remained behind like bleached fossils even as the modern gloss of restaurants, hotels and apartment towers moved in.

Now, a ballet of giant, tightly coordinated engineering works — $4.5 billion worth of building up, tearing down and digging under on the water’s edge — is about to change the city’s storied old coast all over again starting next year. Each of the pieces is major in its own right — a 1.8-mile big-bore tunnel 200 feet below grade at its deepest, an earthquake-conscious sea wall buttressing the piers and an altered city grid that will come with a demolition of the old viaduct. Collectively, they add up to a city on the remake, with a waterfront transformation that will be seismic and aesthetic all at once, not to mention messy and cacophonous.

Hurricane Sandy gets partial credit, city officials said, for bolstering local acceptance of a plan that will mean periodic disruption of commercial and transportation rhythms for at least three years to come. Voters in Seattle cast their ballots last month for a $290 million bond measure to pay for replacement of the most eroded and threatened section of the sea wall — a linchpin of the waterfront package — even as images of East Coast devastation and cleanup filled the news. The measure, which included a 30-year property tax increase to pay for the bonds, passed with 77 percent voter approval.

"It didn’t hurt to have people reminded of nature," said Jennifer Wieland, a transportation planner at the Seattle Department of Transportation.

Local businesses, meanwhile, are bracing for a season of stress, as transportation to and through downtown gets shifted and pummeled.

"Logistics-wise, I’m glad I’m not in charge," said Andy Townsend, who co-manages the Bicycle Repair Shop, a store catering mainly to bike commuters in a former warehouse a block from the water, underneath the 1950s-vintage viaduct highway. Townsend, who opened the business here with a partner last year, said he thought they would survive the construction window. His bigger fear, he said, is the rents that could rise on a more boutique-ish waterfront.

The scope and scale of the work can be partly glimpsed through its numbers:

» 20,000. How many old-growth Pacific Northwest trees that engineers estimate were driven down into the soil to build the original sea wall from around World War I through the mid-1930s. Some timbers are still intact and sturdy; others will have to be extracted like wisdom teeth.

» 57.5. The diameter, in feet, of the tunnel-boring machine that will grind under downtown — the biggest such device, by about seven feet, ever constructed. Picture a grinding wheel about the size of a five-story brownstone.

» 17. Days targeted for a race-the-clock closing of the six-lane viaduct highway when the tunnel that replaces it goes live for traffic, currently scheduled for mid-December 2015.

» 900. Monitoring devices on buildings and under streets and sidewalks above the tunnel route, as sentinels for ground settlement or structural trouble during and after tunneling.

City and state officials, for their part, are hoping the work itself becomes a tourist draw for a certain kind of visitor whose jaw drops at the mighty works of engineers. Construction-inspired art projects and educational or viewing portals could create what Wieland called "the Construction Experience."

Preparations are already under way for a kind of inaugural ceremony around the giant boring machine, which is scheduled to arrive in March in 41 pieces on a specialty cargo ship from a construction site in Japan. It will be assembled in a launching pit about the size of a football field at the tunnel’s southern end.

"I can see it in my mind, just coming in on the ship," said Matthew D. Preedy, an engineer and manager at the state’s Department of Transportation who is overseeing the tunnel and viaduct project. He said he pictured the cargo vessel being greeted by an array of fireboat water cannons shooting in the harbor. "It’s going to be a great show," he said.

Marine scientists who have been working on designs for the sea wall said the suite of habitat structures under consideration — all intended to create a friendlier, safer transit route for juvenile salmon born in rivers south of Seattle and heading north — could also become a kind of eco-tourism draw as construction unfolds, and afterward.

Building on similar ideas from places like Vancouver, British Columbia, and Sydney Harbor in Australia, plans include varied textures on the ocean-facing sea wall surface, to shelflike structures on which tiny fish can pause for feeding or shelter, to light tubes from the surface that could mimic conditions in the shallow shore waters that the salmon would swim through in nature, if they could.

"This is really quite a unique application of ecological techniques to a sea wall," said Jeffery R. Cordell, a principal research scientist at the School of Aquatic and Fishery Sciences at the University of Washington. The underwater light-enhancement efforts alone, which Cordell has been studying and testing for the last few years, could make waves in marine habitat enhancement work. "It’s never been done at this scale," he said.

Some owners and managers of tourist-related businesses have fretted that the aboveground construction season, currently September to May each year, could impinge too much on Seattle’s high season for summer visitors. Other waterfront workers say the concrete and steel viaduct itself, which engineers have said could collapse in a strong earthquake, has cast a shadow so long on the area that the added light, in city known for its seasonal gloom, could be startling.

"I’ll miss the viaduct," said Emily Sands, a sales clerk at a waterfront shop called Exclusively Washington, which sells Seattle mugs, cedar fish-cooking planks and artwork showing people grinning up into the rain without umbrellas. "I know it’s ugly and loud and it’s not safe if there’s an earthquake," she said. "I know it has to go."

Preedy at the Department of Transportation said that managing local expectations, about what could change or not, and how much disruption will ensue before the dust finally settles, comes with his job at the helm.

"There’s a potential for a lot of angst," he said.

© 2012 The New York Times Company