Decks moved into place for Tacoma Narrows Bridge

Taking advantage of low tidal changes and currents, design-builder Tacoma Narrows Constructors relocated the SWAN from Commencement Bay to the site of the new Tacoma Narrows Bridge during pre-dawn hours yesterday morning. The ship arrived at the bridge site around 3:30 a.m., where crews spent the next few hours mooring it under the bridge’s west side span. The SWAN will remain in its new temporary home up through August while its 16 bridge deck sections are hoisted into place.

Assembling the new bridge deck starts the final chapter of the 5-year construction story of the new Tacoma Narrows Bridge. The entire deck-lifting process will take about four months to complete and includes three separate deliveries of deck sections to the Narrows. The deck sections will be lifted into place with gantry cranes that straddle the bridge’s two main suspension cables.

TNC plans to lift the first deck section exactly in the middle of the bridge during a slack tide period within the first two weeks of July. The remaining 45 deck sections will be lifted in an order that, to the casual observer, may appear almost random. It will be anything but. The non-linear order of lifting the deck sections is designed to maintain equal stresses on the bridge’s two towers, which will pull the towers back to a plumb vertical position. (People following the progress of the tower construction may recall that TNC used large cables to pull both tower tops back about two feet toward the shore. They did that because the weight of the new deck sections will pull the towers toward each other and back to a perfectly vertical alignment.)
While the SWAN is moored at the bridge site, the west side span will be closed to all marine traffic. Mariners are encouraged to stay informed of deck-lifting activities and the accompanying marine restrictions by visiting .

Marine restrictions will be in place not only around the SWAN itself, but also around the barge MARMAC and around gantry cranes and other equipment.