By: Roads & Bridges
As the only Potomac River crossing in the southern half of the Washington, D.C., area, the Woodrow Wilson Bridge (WWB) is essential to the region’s road and marine transportation and integral to regional commerce and 70 million bridge travelers each year. The existing six-lane WWB, designed for 75,000 vehicles per day, now carries nearly three times that traffic. And today’s 195,000 daily trips are projected to grow to 300,000 by 2020. Daily backups and congestion, usually many miles long, are made worse by the large volume of traffic entering from adjacent interchanges. Compounding the daily congestion is an accident rate that is twice as high as Virginia and Maryland averages, which stems from inadequate capacity, abrupt merge areas and a lack of shoulders. Two of the major decisions about the bridge replacement reached after a decade of study and planning include:
1. Replace the old bridge with twin side-by-side bascule bridges having higher clearance over the river, reducing bridge openings by an estimated 75%; and
2. Build for flexibility and expansion, ultimately offering 12 lanes: eight lanes to match the eight-lane Capital Beltway, two lanes to facilitate merging and exiting and two lanes for future rail transit, bus service or high-occupancy vehicles.
In fall 2000 the first phase of construction on the new bridge structure began with the dredging of the environmentally sensitive Potomac River channel. Some 340,000 cu yd of mud were removed.
Construction of the actual structure for the new WWB began in spring 2001. The pyramid-like foundation footings to support the bridge’s V-shaped piers were constructed first. Enormous formwork, reaching beyond 70 ft in height, was used to form the cast-in-place concrete piers for the draw span. To increase the service life of the bridge and reduce maintenance caused by corrosion, 23 million lb of epoxy-coated rebar was used in the superstructure. An additional 1.9 million lb of stainless-steel rebar was used in the draw spans decks.
While the WWB will cost $820 million, the total road and bridge project, 7.5 miles long, is budgeted at $2.44 billion. It is scheduled for completion in 2011. Over the life of this massive project, 45 contracts will be generated. Careful and coordinated management by Virginia, Maryland, the District of Columbia and the U.S. Department of Transportation is essential. The first six lanes (southern span) are scheduled to open by mid-2006. Three lanes of traffic will flow in each direction. The old WWB will then be demolished. Two years later, the second six lanes (northern span) will be slated for opening.
The new WWB will reduce bridge openings by an estimated 75%. Connecting beltway and interchanges will allow more efficient and safer traffic flow along with smoother and safer merges and exits. In addition, the finished project is built for future flexibility and expansion.
