ASCE Recognizes Work on Wilson Bridge
When it opened in 1961, the original Woodrow Wilson Bridge was designed to accommodate 75,000 trips per day. By the end of its life it was carrying nearly 200,000 trips and was classified as functionally obsolete. The new Woodrow Wilson Bridge project replaced nearly 12 percent of the Capital Beltway (Interstate 495/95) and created four new interchanges while implementing numerous projects and programs to protect the local environment.
The American Society of Civil Engineers presented its 2008 Outstanding Civil Engineering Achievement Award to the Woodrow Wilson Bridge project at its annual gala in Arlington, Va.
"For years, Washingtonians and visitors have faced some of the worst traffic on the East Coast," said ASCE President David G. Mongan, P.E., F.ASCE. "The dedication and innovation of the Woodrow Wilson Bridge project team produced a bridge that both eased traffic congestion and implemented techniques to protect the environment during and after construction."
Due to soil conditions, arches similar to other monumental bridges in the nation's capital could not be constructed at this location. Instead, the new bridge features V-pier structures, to support variable-depth plate girder spans, creating the arch appearance without the large horizontal thrusts of conventional arches. Innovative application of segmental construction methods accommodated both balanced cantilever and out-of- balance construction techniques for the precast, post-tensioned V-piers. During construction, the old bridge was used as a trestle to build the inner loop span—saving six acres of dredging and preserving fragile underwater vegetation.
Upon experiencing a fish kill from large-diameter pile driving near the navigation channel, the project team tried infusing air bubbles around the pile to cushion the shock, which eliminated impacts to the fish population. And, working with the Maryland Department of Natural Resources, the project team used inert debris from the old bridge to create new fish reefs in the Chesapeake Bay. A total of 60,000 tons of debris was deposited in five open-water reefs, making the effort the largest enhancement to artificial reefs in Maryland waters in 20 years.
The project included an environmental mitigation program, which used a holistic and watershed-based approach to link local and regional environmental needs. The program—the first of its kind attempted in an urban setting—restored 26 miles of historic spawning habitat by removing or modifying 23 man-made barriers to fish passage in five major streams located in the D.C. area. The design focused on two solutions that mimic natural stream channels: the riffle grade control structure and flow constrictor/step pool. Most sites, now in their second or third year of monitoring, are exceeding expectations and fish are passing upstream through the new structures for the first time in decades. Additional mitigation efforts included park land improvements, reforestation, wetland creation, fishery restocking, submerged aquatic vegetation planting, and replacement of an abandoned landfill along the Anacostia River with more than 23 acres of tidal wetlands.