Crews dig deep to build bridge

The Purple Heart Bridge over the Occoquan River is being widened to catch up with years of traffic growth in Northern Virginia.

The bridge, built in the early '90s, links Prince William and Fairfax counties and has long been known as a major bottleneck along Interstate 95.

The $123 million widening project will add a fourth lane to I-95 between Occoquan and Springfield, on both sides of the highway. When completed, the new lanes are expected to alleviate traffic congestion along the six-mile portion of the highway.

It is being constructed in three phases -- the first two are the widening of the north and southbound sides of the highway in Fairfax County, and the third is the addition of the fourth lanes on the bridge.

At a cost of $10 million, phase three will widen the bridge to eight lanes, or 10 when you include the High Occupancy Vehicle lanes.

Virginia Department of Transportation Project Manager Charlie Warraich said 16 new shafts will have to be bored into the river bed and 10 new columns will be constructed to support the wider structure.

Work on the I-95 widening project started nearly two years ago, but the bridge work started in January. Crews were not permitted to begin working in water until July 1 because of environmental concerns about the health of the river.

But as drivers cross the bridge at speeds of 55 mph or more during normal traffic conditions, they can't see what's going on below the deck.

Filling the hole

According to the design, Warraich said, 16 new holes, or drill shafts, will be bored into the riverbed to support the columns for the wider bridge.

The water near the river shore is relatively shallow at about five or six feet deep, but in the middle of the river where pleasure boaters frequent the channel, the water can be up to 50 feet deep underneath the bridge, said Warraich.

Crews must drill until they reach bedrock, and then, drill an additional 30 feet into the rock before they are finished. Warraich said crews never know what to expect when working on the river bottom.

"You can go across to the other side of [U.S. 1] and its hard rock on the bottom and then you can go to the other side it is all soft," said Warraich.

Once the hole is bored, a metal pipe is put in place and filled with concrete. The concrete rises to the water's surface.

Warraich said it can take nearly a month for the material to harden so it can support the weight of both the bridge and the cars that travel across it.

The project is being completed in a fraction of the time it took crews to build another bridge across the Occoquan River on Va. 123, which also links Prince William and Fairfax counties.

Crews working to build the six-lane bridge at the Town of Occoquan, which opened in 2007, employed a cofferdam, an enclosure that displaces the water, thereby creating a dry work environment.

Warraich said this method is far more costly and time consuming than what is being done at the Purple Heart Bridge.

"If we used a cofferdam then each drill area can take up to four or five months versus the about a week-and-a-half it takes for us to drill directly in the water," he added. The Va. 123 bridge used a cofferdam because the project was on a much larger scale than the highway bridge.

After the holes are drilled and the concrete hardens, Warraich said he can then shift his focus to work that needs to be done out of the water.

"Getting out of the water is our biggest challenge, because once we do, I can say 'Now we have [the beginnings of] a bridge.' "

Environmental safety

About 1,000 yards away from the construction area are the wetland grasses and birds that call the Occoquan River home. On the shoreline above the wetlands is black sediment fencing to stop the erosion the construction causes.

The entire construction site takes up less than one-tenth of an acre of wetlands, Warraich pointed out.

From additional dirt or mud to trash and waste, Crews cannot leave anything in the water that was not there before they came. The river sludge extracted from the drill shafts is loaded onto one of five barges at the work site and than taken to another location along the river, and then dumped on the shoreline.

Trash is also removed from the water.

"We want to work in a safe environment, plus we want to make sure that the river is as clean the day we leave as it was when we got here. Any trash goes into the receptacles on the barges and if you see something floating out on the river, regardless if we put it there or not, we pick it up," said VDOT project consultant Joel Barker.

Barker has a constant eye on the nearly 30 construction workers, from two separate contracting agencies, who work on the project. Much of his job is to ensure the safety of the men during their shifts. At a minimum he makes sure that everyone working on the river is wearing a life vest in the event they fall into the water.

The work on the river is bound by strict time constraints, so many crews take advantage of what time they do have to get the job done to plan ahead of schedule, said Warraich.

On Feb. 15 crews will have to come out of the water and stay out for more than five months while fish in the river begin their mating season.

A new bridge

In the end, the expanded bridge has a final price tag of about $10 million -- $5 million allotted for each side

It will have four new abutments -- which support the bridge on the shore -- that were finished in January, 10 new piers in both water and on land to support bridge columns, and 16 new drill shafts.

At a total length of 865 feet, with two new lanes with a width of nearly 13 feet, Warraich said about $3 million worth of concrete will go to pave the new road surface.

Steel beams worth $2 million, each about 150 feet long, will be spliced to span the entire length of the bridge starting next summer.

Phase one of the project could open sometime later this year, with phase two opening in 2010. The bridge will not be completed until 2011.

Staff writer Uriah A. Kiser can be reached at 703-878-8065.