The Virginia Department of Transportation is launching a new phase this week in the reconstruction of the Fairfax County Parkway’s busy junction with Fair Lakes Parkway.

Starting as early as today, drivers won’t be able to go directly between Fairfax County Parkway and North Lake Drive. This is a permanent closing, part of the plan for the new interchange.

Once sound walls are placed across North Lake Drive, a cul de sac will be built. Residents in the Villages of Fair Lakes will use Route 50, to the north, for access to their homes.

VDOT’s $69.5 million interchange construction project, assisted by Fairfax County and a big infusion of money from the federal stimulus program, is rebuilding one of the oldest and most congested stretches of the county parkway.

The project will open in phases, but all the work, including the final paving, should be done by October 2013, VDOT said.

The parkway will be widened from four to six lanes from south of I-66 to Rugby Road, a distance of about three miles. Signals at Fair Lakes Parkway and Monument Drive will be eliminated. Long ramps will provide separate access to and from Fair Lakes Parkway and nearby Monument Drive.

Traffic on Fair Lakes Parkway and Monument Drive should flow more easily, because of the separation of local and county parkway traffic

Shared-use paths and sidewalks will allow for pedestrian and cyclist access at the interchange and also to the Rocky Run Stream Valley Park trail system.

Weekend work

From 7 a.m. Saturday to 5 a.m. Monday, Monument Drive at the Fairfax County Parkway is scheduled to be closed as workers install a 30-inch storm drain pipe across Monument Drive. A detour will be posted directing traffic as follows:

County parkway traffic heading for Monument Drive will be detoured onto Fair Lakes Parkway. From Fair Lakes Parkway, turn left onto West Ox Road and left onto Monument Drive.

Traffic coming from Fields Bridge Road and Fair Ridge Drive wanting to go west on Monument to the county parkway (Route 7100) will be directed to turn right on Monument Drive, turn right on West Ox Road and right on Fair Lakes Parkway to Route 7100.

Traffic coming from Marley Garden Lane, Fields Bridge Road, Fair Ridge Drive, Monument Court and Vernoy Hills Road wanting to access Route 7100 will be directed to turn left on Monument, right on West Ox Road, right on Fair Lakes Parkway to Route 7100.

If it rains, VDOT said, the weekend closing will be postponed until the weekend of June 18 so that it does not conflict with Celebrate Fairfax, the county’s annual fair.