Highway officials yesterday announced milestones at two of the region's major road projects, with key work shifting to land at the new Woodrow Wilson Bridge and an important lane shift about five miles down the interstate at the Springfield Mixing Bowl.

Builders of the new Wilson Bridge announced that water has been drained from soil in a marshy area on the Virginia shore where a widened Capital Beltway will be built, marking the first time that crews have completed a portion of the project on land. Similar work is proceeding on the Maryland shore and is expected to be completed by year's end, officials said.

Bridge officials said the 2 1/2-year, $35 million project between Telegraph Road and Route 1, along the banks of Cameron Run and Hunting Creek, was completed late last month. The work clears the way for all projects on the Virginia shore, including widening the Beltway and building lanes, ramps and bridges for reworked interchanges.

"This literally lays the firm groundwork for all the roadway improvements that will go forward," said John Undeland, spokesman for the project. "You don't build a highway on shifting sands, and what we're doing here is making sure the foundation for the roadway is firm and solid."

The Wilson Bridge and Mixing Bowl projects are two of the largest public works efforts in the country, both designed to alleviate chronic choke points on some of the Washington area's most heavily traveled roads. Planning for the projects has been underway for years and, despite setbacks at various stages on both, construction on each is at about the halfway point.

The $2.56 billion Wilson Bridge construction project, scheduled to be finished in 2008, aims to replace a span that carries about 200,000 vehicles a day, many more than the 75,000 it was designed to carry. Construction on the 12-lane bridge began in 2000, and so far most of the work has occurred away from traffic in the Potomac River.

But work on land that will impact traffic is expected to accelerate over the next several months, after the completion of the soil project and with the launching of construction of a new Route 1 interchange and a revamped Telegraph Road interchange.

Also, Undeland said that one of the four lanes on the Washington Street overpass spanning the Beltway has been closed so crews could begin work on a new overpass. He said one lane is reversed during the day to serve commuters, leaving a single lane for traffic heading against the rush-hour flow.

On the Maryland side, work on a new Interstate 295 interchange has expanded.

Bridge officials were particularly proud of the soil work, which they say involved two unusual methods to drain a porous base that had been wet for "millennia." To dry it out, they stuck "wicks" -- straws made from industrial fabric -- as much as 40 feet into the ground to suck out the moisture.

Workers then strengthened the soil by injecting cement, again as much as 40 feet deep, a practice not widely used in the United States. In all, 163,000 cubic yards of soil and cement were mixed, officials said, forming a solid base.

Officials acknowledged that the area would require monitoring to ensure that it holds firm and that the new highway isn't bedeviled by sinkholes. "That's a valid concern and there's a lot of monitoring to make sure it's staying put," Undeland said.

Drivers heading east from the bridge toward the Mixing Bowl will find themselves traveling on a reconfigured Beltway.

Virginia transportation officials said that four newly paved inner-loop lanes opened yesterday on the three miles between Van Dorn Street and Interstate 95 at the Mixing Bowl. Two of the old Beltway lanes were redirected into the new ones, while two others will be reworked and eventually become part of the outer loop, project officials said. The $700 million Mixing Bowl project at the intersection of Interstates 95, 495 and 395 is scheduled to be completed by the end of 2007.