A bridge to the future arrives

Photo by rocky ross

VIEW FROM ABOVE. Around 50,000 people showed up for the chance to walk across the new bridge July 15.

The new Tacoma Narrows Bridge is more than just thousands of tons of concrete spanning a body of water. The $849 million structure is a marvel of modern engineering. If everything goes according to plan, it will reduce congestion in an area that has long been a major chokepoint for traffic jams in the Puget Sound region.

The bridge's origin goes back to 1998, when South Sound voters approved a ballot measure authorizing its construction, financed primarily by bonds that will be repaid by tolls.

A public-private partnership was formed between Washington State Department of Transportation and Tacoma Narrows Constructors, a joint venture between construction giants Bechtel and Kiewit Pacific. Construction began in October 2002.

In early 2003, work began on the caissons, massive concrete and steel foundations that support the bridge towers, in a Seattle shipyard. They were transported to Port of Tacoma for further work.

That summer the two caissons, which weigh 85,000 tons each, were hauled to the Narrows by tugboats.

After six months of placing concrete within their walls, they were sunk into the seabed in December 2003 and January 2004. By summer 2004, after considerable dredging, the installation was completed.

Construction on the towers began that August. A major difference between this bridge and the second one is that its towers are made of reinforced concrete, rather than steel. When finished, they stood 510 feet above sea level.

Massive concrete blocks called anchorages were buried more than 60 feet into the earth, one on each side. The anchorages support the tension of the cables and bridge deck.

Fabrication of the suspension system began in summer 2005. The ends of the main cables are held by the anchorages. A line attached to the anchorage was brought across the water by a skiff. When it reached a tugboat, workers pulled it on board. They connected it with steel wires lowered from above to steel plates.

Cable spinning began in October 2005 when crews pulled the first steel wire from the Tacoma anchorage over the towers to the Gig Harbor anchorage. The spliced wire made 2,024 round trips, with an eventual 19,000 miles of cable installed.

The last major phase was piecing together the one-mile roadway, which consists of 46 sections. The first batch arrived in June 2006. They were lifted into place with special hoists called gantry cranes.

Whereas the deck of the 1950 bridge is made of lightweight concrete, the deck of the new bridge is made of steel plates with beams running lengthwise and crosswise. This design enables the bridge to better handle heavy loads, high winds and even earthquakes. Once installed, it was covered with two inches of asphalt.

It was designed so a second deck, for either vehicle traffic or light rail, can be added in the future.

Over 50,000 people took part in opening day festivities July 15. They were drawn by the sense of being part of history. Many hit tables where they could cut a piece of ceremonial ribbon, and visited stations where they could have a "passport" stamped indicating they had walked the entire span.

Some made a statement as they strolled, waving American flags and hoisting signs expressing support for the troops. A trio of Star Wars fans dressed as Darth Vader and two of his storm troopers.

A ceremony honored the work of two elected officials who were champions of the project and passed away before its completion, State Senator Bob Oke and Representative Ruth Fisher.

Several dignitaries spoke during the official dedication ceremony. Governor Christine Gregoire said 3.5 million work hours went into the project. She described those involved as "the best work force found anywhere in the world."

Gregoire described the new bridge as an engineering feat all Washingtonians can be proud of. "This is a symbol of a bridge to our future," she added.

Compared to the first and second bridges, the emphasis on safety on this one "has been like night and day," said Project Director Jeff Carpenter. "The big driver has been Tacoma Narrows Contractors." Any worker engaging in unsafe behavior was sent away from the job site, he added.

Linea Laird, the state's construction engineer, said the emphasis on safety was greater than on any other project she has been involved with. "The commitment was there. The workers took much honor and pride in their work," she said. The safety record was especially impressive considering some of the inclement weather conditions workers faced, she added.

Both Carpenter and Laird listed corrosion deposits on wire wrapped on reels waiting to be spun into the main suspension cables as the most challenging hurdle to overcome. Inspectors discovered this in November 2005. About 20 percent of the wire was unusable.

Carpenter said suppliers in China and South Korea were quickly located to supply new wire, but it threw the project four months behind schedule. This caused the deck lifts to occur during bad weather, he noted.

Laird said it generally takes a year to order such a large amount of the wire. The contractor and WSDOT sent inspectors to factories to certify the quality of the replacement wire.

"It required significant adjustments," she explained. "Everyone worked so hard to make it happen."

When engineers of the future study this bridge, what will they consider to be unique about it? For Carpenter, it will be the sinking of the caissons. The process of slowly sinking them required displacing water equivalent to draining Lake Washington three times a day. "That was very groundbreaking," he noted.

Laird believes the bridge can send a statement to Washington residents that the state government can deliver major transportation projects. It came in under budget and was just a few months beyond the targeted completion date. The process was transparent and construction was well managed, she said. "This is something we can build on."

All who were involved in building the grand structure, from laborers to welders to engineers, can take a great sense of pride and accomplishment now that it is finished, according to Laird.

"It far exceeds my expectations," she said. "It just makes me feel so proud."

Carpenter said he was surprised by the number of people who worked on both the first and second bridges he met over the last five years.

"Most civil works projects, we go in and do the job, and people take it for granted," he continued. He doesn't think that will be the case with the bridge. "People on both sides identify with the bridge. This bridge really does become a symbol of Gig Harbor and Tacoma."

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