Route 37 Project to Feature Innovative Intersection Design

IMPROVEMENTS from page 40

“The Route 7 project is large and complex, but we decided to try to get it all done at once, rather than have to come back again soon with more disruptions,” he said. “From the beginning of the job, we worked closely with people from the nearby neighborhoods so they could advise us about their interests and concerns. Then, we did our best to cooperate to see how we could address those concerns in the project.”

Of course, the construction team had to maintain traffic on this busy thoroughfare during the many upgrades. The work has required more than 50 traffic shifts to accommodate the paving and construction. The work has required multiple crews working on various parts of the project at the same time.

The new lanes are 21.5 in. thick, with 6 in. of cement-stabilized subgrade, 6 in. of cement-treated aggregate and 9.5 in. of asphalt. Superior Paving of Gainesville produced the 306,000 tons of asphalt required for the project. The work also used 310,000 sq. yds. of soil cement and 230,000 tons of stone.

As with many of its projects, VDOT has allowed 32 to 35 percent of recycled asphalt pavements in the mix. The department has found through studies and observation that this amount of recycling saves costs, saves the environment and still provides quality pavements.

Challenges

The complexity of the project provided planners and construction teams with numerous challenges.

“We needed to sequence our construction so that we would not impact sensitive wetlands near a bridge area,” said Rahman. “We also have done our best to make minimum impact to properties in the 36 homeowners associations we worked closely with. We worked carefully along easements that were outside of our construction zone. In some areas, we built sound walls on top of the retaining walls. In all, we built 7.2 miles of sounds walls to minimize the sound impact of traffic to the surrounding communities.”

Other challenges included working around cemeteries and historic properties, including Colvin Run Mill Park. Built around 1811, the mill is the only operational 19th-century water-powered mill in the Washington, D.C., metropolitan area.

The project team constructed retention ponds to handle runoff and relocated the Colvin Run stream.

“When the team constructed the third lane on Route 7, we needed to relocate a 20-footwide stream,” said Rahman. “We brought in about 40,000 square feet of concrete blocks to form a new straight channel for the stream.”

This design minimized impacts to adjacent wetlands and park property while providing protection against future erosion of the stream banks.

Project designers incorporated an innovative intersection design of a “displaced left turn lane” at Lewinsville Road to help eliminate this chokepoint on the busy corridor. Intersections can be troublesome when vehi- cles, pedestrians and cyclists all intersect. A displaced left turn is a way to get more cars through a space than a conventional intersection would allow and to do it with fewer conflict points. This can increase the capacity of the intersection by as much as 70 percent. Signal coordination throughout the corridor also is enhanced. Raised islands also are utilized to channel the traffic and aid pedestrians crossing the traffic.

“We used the displaced left-turn concept in one other location in Virginia,” said Rahman. “This is the second time it has been used in the state, and it looks like it will be very effective.”

Shirley Contracting and its team used skid steers, excavators, dozers, pavers, rollers and cranes on the project. On several occasions, the construction team used innovative applications of Universal Total Stations (UTS) survey systems for the GPS guides. This has been found to help in increasingly exact applications of earth, rock and pavements.

In any project of this size and complexity, planners need to manage right-of-way land acquisitions.

“This area has a dense population, but we were still able to reduce easement impacts to adjacent parcels by 7.4 acres,” said Rahman.

“In my 20 years with VDOT, this is the most challenging and interesting project I have ever been a part of.”

“We see the money NVTA has invested in the Route 7/Tysons corridor as well-spent, especially when it gets people home to their families faster,” said Martin E. Nohe, former chairman of the Northern Virginia Transportation Authority, and Prince William County’s former Coles district supervisor at the project’s groundbreaking in 2019. “As our region’s population and employment continues to grow, these types of improvements that provide alternate modes of travel for motorists, cyclists and pedestrians alike are critical to improving safety and reducing congestion.”  CEG