Entering its fourth year of construction, the Woodrow Wilson Bridge project is the third-largest of its kind in the nation. But unlike some megaprojects, this financial house is in good order, with 22 of 27 contracts thus far having come in under estimate. What's more, contracts to date have seen minimal change orders and have not experienced appreciable delays. Sixteen more planned contracts remain to be bid for Virginia and Maryland work, meaning that nearly two-thirds of contracts are either completed or presently active.
The seven-and-a-half-mile project will replace the existing six-lane span with two six-lane, 6,000-ft spans and significantly upgrade four nearby interchanges. The new bridge is designed to be transit-ready for HOV or hard rail and to serve motorists for 100 years. To better serve motorists, pleasure boaters and commercial vessels, it will be about 28 ft higher to provide extra clearance so that bridge openings will be reduced by 75%--to about one per week.
The project's work is ramping up on several fronts:
* $491 million worth of work is under way on three bridge superstructure contracts. Earlier contracts to dredge and build foundations, totaling over $145 million, are already complete;
* $96 million in work ongoing for over two dozen bridges on the Maryland side to accommodate a wider Capital Beltway and upgrades to the southern part of the I-295 interchange;
* 245 residents and 15 businesses were relocated six months ahead of schedule on the Virginia side to clear the right-of-way for the expansion of the U.S. Rte. 1 Interchange and widening of the Beltway;
* $130 million in work continues strengthening soft soils between Telegraph Road and U.S. 1, replacing the Washington Street overpass, widening the Beltway to align with the new six-lane southern bridge and building 11 southern ramp bridges of a new U.S. 1 interchange;
* A $200 million contract to upgrade the rest of the U.S. 1 interchange has been advertised for construction bids; and
* A $16 million contract to begin the upgrading of the MD 210 interchange will be advertised this month.
"Extraordinary engineering"
Most of the completed bridgework is hidden beneath the Potomac River, where more than 600 steel pipe piles were driven over 200 ft underground into the river bed during the first year of the project. The largest piles--210 ft long and 72 in. in diam.--were driven by a pile driver suited to building oil platforms.
American Bridge and Edward Kraemer and Sons is the joint venture building the bridge's bascule drawbridge, by far the most technically challenging aspect of the bridge. It features twin drawspans, each with four leafs, that contain more than 14 million lb of structural steel. The V-shaped pier foundations for the bascule must be strong enough to withstand the cycle of openings--5,000 times over the next 75 years--and the 300,000 daily vehicles projected by 2020. The contractor is using temporary supports or falsework to form the piers as they are cast in place. The supports and formwork are reusable for each of the four bascule piers. The first pair of bascule piers will take nearly a year to build. In all, the bridge above its pedestals will use more than 40,000 cu yd of concrete. The bridge's other V-piers will be poured in sections on the shores of Maryland and Virginia and then barged to the bridge and put together.
While architecturally beautiful, the arched design requires careful design and detailing. "It's quite complicated," said Bob Healy, deputy chief bridge engineer for the Maryland State Highway Administration (MSHA), which is in charge of the bridge and Maryland portions of the project. "We're trying to do something that's unusual because the loads from the bascule superstructure are not centered directly over the foundations. Due to the way the V-piers cantilever out from their foundations, we have to do some extraordinary engineering to transfer those loads."
Resembling flexed muscle fibers, the steel tendons running through the concrete piers will be tensioned between the arch pieces, distributing loads throughout the V-piers. The drawbridge leafs must be carefully erected and positioned. Each set must be placed with delicate precision with tolerances as close as 1/8 in., so that the draw span will open and close reliably regardless of the elements--heat, cold, rain, wind, snow and ice, not to mention all the traffic--for years to come. The complex machinery that will open and close each span will only require about 150 hp--the equivalent of a Dodge Neon engine--because each drawspan's weight is finely balanced between the deck and its counterweight.
The six-lane southern span is scheduled for completion by early 2006, when traffic will be shifted onto it. The existing bridge will then be demolished to make way for the northern span or Inner Loop to take its place by 2008. Six lanes will be striped for general travel, four lanes for express traffic, with two additional lanes for future transit or HOV lanes, noted Bob Douglass, MSHA project manager.
Moving traffic, holding eagles
"Where do I start on the challenges?" asked Ronaldo Nicholson, P.E., VDOT project manager. On land, the twin challenges of soft soil and highly sensitive natural and human environments are major concerns. So too is building around already-congested traffic and keeping it moving with minimal delays. "We're quite fortunate to have a talented team of innovative and skillful engineers and contractors who are equal to every challenge."
New state-of-the-art methods of soil column mixing and pile supported embankments are being used to strengthen the highly organic and plastic soil areas adjacent to the Beltway in Virginia. Wick drains have been used extensively in order to more rapidly remove moisture from underlying clay deposits in both Maryland and Virginia. Used in combination with temporary surcharging, these wick drains will speed up soil settlement by several years.
Sensitive to motorists and truckers already burdened with area gridlock, VDOT and MSHA are requiring contractors to perform traffic-affecting work during off-peak hours in order not to tie up lanes. For example, as the Washington Street bridge in Alexandria, Va., is being extended requiring the elimination of one of four lanes, a carefully planned operation of reversible lanes has meant that motorists have experienced almost no traffic impacts.
Strategically timed early in the project to help motorists navigate through the work zone as well as after it is completed, a $1.5 million intelligent transportation system of cameras and variable message signs will be ready by the end of this year to better inform motorists of traffic accidents or congestion. The project also coordinates its activities with more than 100 local officials at fire and police agencies, the media and local transportation agencies, including traffic operations centers in Maryland and Virginia.
Building with maximum environmental sensitivity also is a core project ethic. A full-time environmental team backed up by an independent monitor ensures construction sites are kept clean and do not affect the outside environment. Miles of silt fence encircles disturbed areas, and water quality monitors that run 24 hours a day track construction.
To compensate for unavoidable impacts to environmental resources in the path of the project, a $50 million mitigation program is being implemented. Among the environmental projects are the planting of environmentally beneficial river grasses in several Potomac River locations reaching as far away as the Chesapeake Bay, 90 miles downriver from the bridge, and an 84-acre bald eagle sanctuary where the bridge touches down in Maryland. Overall, 12 contracts are dedicated to environmental projects.
The most dramatic evidence of environmental sensitivity is the successful hatching and fledging of bald eagles nesting immediately adjacent to the project. The traditionally human-shy eagles and eaglets are carrying on as if in a national forest instead of next to an enormous construction site and busy highway.
