Tacoma Narrows Suspension Bridge, WA, USA

Washington State Department of Transportation (WSDOT) has secured a ruling allowing it to proceed with what will be the Tacoma Narrows' third bridge. The first bridge, built in 1940, proved to be too susceptible to strong winds and was nicknamed 'Galloping Gertie' by locals. Following its collapse in November 1940, the bridge was replaced in 1950 by the current bridge. The third bridge, due to be completed in 2008, will not replace the second bridge but will span the Tacoma Narrows parallel to and south of it.

The SR16 corridor (which the bridge is on) is used by 85,000 to 90,000 vehicles per day and this figure is expected to rise to 120,000 vehicles per day by 2020. The capacity of the second bridge does not even meet current requirements so, as part of the project, it will be reconditioned and brought up to current seismic standards so that it will be the westbound route and the new bridge the eastbound one. On top of this and the new suspension bridge a 3.4-mile stretch of SR16 will be improved by adding an extra lane to it and introducing new interchanges and a new toll plaza.

The design-build contract is being overseen by Tacoma Narrows Constructors, a joint venture of Bechtel, Inc. and Kiewit Pacific.

NEW TACOMA NARROWS BRIDGE

The new bridge, being designed by a Parsons / HNTB joint venture, will be 5,400ft long and will comprise two eastbound general-purpose lanes, one HOV lane and a bicycle/pedestrian lane. In addition to this, the new Tacoma Narrows bridge will have the structural capacity to carry a light rail line or an extra highway lane if needs be.

With a centre length span of 2,800ft this will be the longest suspension bridge built in the USA since the Verrazano Narrows Bridge was opened in 1964. Over 45,000t of steel will be used in the construction and the bridge will be held in place at either end by over 23,000yd³ of anchoring concrete.

SECOND TACOMA NARROWS BRIDGE UPGRADE

The second Tacoma Narrows Bridge will be upgraded as part of the new bridge project. The present bridge configuration is two non-standard lanes in each direction with metal grates between the lanes; it has no central dividers or shoulders. The upgrade will convert it from this state to a three-lane, westbound-only route with standard width lanes, a uniform driving surface and an exterior shoulder.

HIGHWAY AND INTERCHANGE IMPROVEMENTS

A 3.4-mile stretch of SR16, stretching from the Jackson Avenue interchange in Tacoma to a new interchange at 24th/36th Streets in western Pierce County will be upgraded with an extra lane to help ease traffic flow once the project has been completed.

SR 16 is a strategic segment of the National Highway System and, as part of it, the Tacoma Narrows crossing is the only land link across Puget Sound. The highway links the I-5 corridor with the Kitsap and Olympic Peninsulas and provides important access to several military installations and Olympic National Park.

TOLL PLAZA

To begin with, a $3 toll will be charged to use the new Tacoma Narrows bridge. This will be collected by a new toll plaza to be installed by TransCore. The toll plaza will feature both manual and high-speed electronic collection facilities, the latter allowing traffic to be tolled without slowing down. Automatic vehicle identification technology, coupled with a violation enforcement system, will allow this to be done.