The Woodrow Wilson Bridge Project is replacing almost 12 percent of Interstate 95/495 (the Capital Beltway) with two six-lane bridges, four new interchanges and beltway improvements throughout its 7.5-mile corridor. The entire $2.47-billion mega project is nearly 75-percent complete. Virginia's portion of the project includes widening Washington Street into Alexandria and widening the Capital Beltway from four lanes to six lanes in each direction to tie into the new bridge, and the Route 1 and Telegraph Road interchanges, two major north-south corridors into the District, the Pentagon and Crystal City.
According to Ronaldo "Nick" Nicholson, P.E., VDOT project manager, VDOT sequenced the projects based on two major challenges — time and congestion.
"We had to meet the timing of the bridge," says Nicholson. "We started at the eastern approach with our tie-in project, which was a $54-million project to tie in the existing Capitol Beltway with the new spans of the Woodrow Wilson.
"It was linear construction. We could have attempted all three major contracts at the same time, but that would have tied up the north-south corridors of the area. As part of our congestion management, we decided to stagger these projects so we could have enough capacity on the main line I-95 to receive capacity from the bridge, but at the same time keep traffic moving through the developed area.
"We started with the tie-in to receive traffic on the outer loop, then Rt. 1, which was the major route to complete for receiving traffic on the inner loop. We're going back for Telegraph Road, the largest contract. This will basically complete the program."
Work began in December 2001 with a $35-million ground improvement contract between Rt. 1 and Telegraph Rd. By February 2003, work had started on the $55-million Rt. 1 tie-in project. Both projects employed innovative measures to improve the soils.
"When we looked at the project, we were widening the Capital Beltway on mud," says Nicholson. "In order to get the width to be compatible with the bridge, we looked at a state-of-the-art grout improvement program. That program consisted of things that hadn't been done in Virginia or the United States before with regards to strengthening or building work platforms to begin this major heavy construction effort."
These strengthened soils were necessary to accommodate the equipment and materials for building the supports of the new bridge piers and became the base of the new road bed for the additional lanes on the Capital Beltway.
The program included pile supported embankments, Low Density Cementitious Fill (LDCF) and Geofoam, several of which are the first applications on the East Coast.
In the early stages of the project, the pile-supported embankments consisted of soil cement columns on a 3-foot regular grid pattern. A three-pronged auger was used to simultaneously drill down 40 feet deep and insert cement. Later, 18-inch concrete displacement piles with a cap were used to build platforms for the embankments, which were then followed by normal embankment and paving sections.
LDCF was also used to strengthen the soils behind the abutments of the Woodrow Wilson Bridge. LDCF is a flowable, self-leveling material — a "liquid soil" that hardens and rapidly develops load-bearing properties with no compaction. The benefits of LDCF are its speed of application. The flowable characteristics of the material mean it can be readily placed in tight or restricted-access areas where placing and compacting fill is difficult. Flowable fill is also an ideal pavement base material because it will not settle or rut under loads.
Finally, VDOT employed Expanded Polystyrene (EPS) Geofoam, which looks like Styrofoam, to fill in and support an area behind the abutment of the new Rt. 1 overpass. Geofoam is 100 times lighter than most dirt and approximately 20 times to 30 times lighter than other fill alternatives, yet it provides enough rigidity to support a roadway and traffic.
Because the soil in the area of the Rt. 1 interchange is so soft and unstable, typical fill alternatives would have resulted in settlement that would have impacted an underground sewer line in the area and potentially affected the new roadway over time. The Geofoam essentially reduces the net loads on the soft soils to eliminate differential settlement conditions.
"The advantage is that it's a quicker construction method than having to wait for (surcharge and) vertical drains, which would have been our normal process," says Nicholson. "This would have taken four to six months. By going to Geofoam we were able to collapse that to 30 days to 60 days depending on the scope of the work."
Once the Geofoam is placed, it will be covered with a concrete load distribution slab, and then normal paving operations can proceed.
A part of the Rt. 1 Interchange tie-in contract — and a major project in itself — is improvements to the Washington Street overpass into Alexandria. Work included widening the existing overpass to four lanes and lengthening it to accommodate the wider beltway. The new overpass is bordered by wide sidewalks, a bike-pedestrian path and extensive landscaping. For residents it has become a gateway into the city.
Work on the major portion of the Rt. 1 Interchange project, the second largest VDOT contract in state history at $147 million, began in December 2003 and is about 65-percent complete. The scope of work includes constructing the remaining Rt. 1 bridges and interchange ramps, mainline roadway pavement, and reconstructing and widening Rt. 1 from Huntington Avenue to Franklin Street.
Throughout the project VDOT has had to manage the flow of 200,000 cars a day through the construction corridor. "The biggest challenge is to lay out a maintenance-of-traffic scenario three, four, five years or more and then scheduling construction accordingly," explains Russ Fuhrman, executive project manager with Potomac Crossing Consultants. "What makes or breaks a contract is getting all of that right on the front end to minimize contractor risk.
"We have to keep traffic flowing in an east-west interstate direction and a north-south direction from Northern Virginia into the District, so it's a very sequential construction process. Our contractors can't do a whole lot of things at the same time. They have to finish one section, move traffic over and start another piece. It's very complicated and very inefficient from a contractor perspective."
This type of linear construction becomes even more complicated when unknown utilities or differing site conditions slow down the process. "You try to find (creative) ways to make up for that schedule loss," says Fuhrman. "Rt. 1 continues to be a challenge from that perspective as we work our way through this very congested area."
Learning from their experience on Rt. 1, VDOT chose to begin work on the Telegraph Road interchange with a $17-million advance utilities contract in August 2005; the work is 97-percent complete. The scope of the work includes relocating utilities and building underground duct banks for future underground installation of power and telephone lines; relocating transmission towers and overhead lines; and installing sewer and water lines, which requires clearing of trees and vegetation.
"In constructing in an urban environment, the biggest challenge is what you don't know, and that's underground," says Fuhrman. "We've had all kinds of challenges and surprises on Rt. 1 and Telegraph Rd. We found sewer mains that were where they weren't supposed to be. We've found abandoned gas tanks from old service stations that we didn't know existed. On Telegraph Rd. we found foundations from old high line towers that were abandoned, but the foundations were still underground. We would jack and bore or microtunnel utilities and run into these, and we'd have to figure out how to move or go around these concrete structures.
"We're at the stage right now where we're just about through with all of that. It's taken longer to complete these utility contracts; however, these contracts weren't on a critical path, which starts when our major contractor begins work next spring. Hopefully all of this utility work will be out of the way, and we won't have any surprises when the contractor does the underground foundations work. We feel good about that."
The contract for the major portion of the Telegraph Rd. Interchange, which has only recently been let, will be VDOT's largest one to date at approximately $175 million to $180 million. Work is set to begin in spring 2008 and is scheduled for completion in 2013. Although similar in size and complexity to the Rt. 1 Interchange project, VDOT was able to expand the scope of the Telegraph Rd. Interchange due to savings on the Rt. 1 Interchange. In addition to improving the capacity on the mainline, VDOT is eliminating major congestion choke points at Huntington Rd. and Kings Highway by putting in grade separations.
While the Telegraph Road Interchange represents the last 25 percent of the entire Woodrow Wilson Bridge program, Nick Nicholson stresses, "We're not done yet. We don't want to give a false sense of hope that because the bridge is opening that all of the improvements are here. The total relief that the program will yield will not come until we start opening up the Telegraph Road improvements. This was a major program, but we still have another five years to go."
Additional material provided by the Virginia Department of Transportation and the Portland Cement Association. n