Work has begun on Foxfield, a 200-acre planned community of 653 town houses and single-family homes in Fairfax County, the developer, Carr Properties Inc., has announced.

The project is located on the north side of Route 50, approximately 2 1/2 miles from Route 66 and Fair Oaks Mall. Homes will be constructed by three builders: NVHomes, Ryan Homes, and Edw. R. Carr and Associates Inc.

Prices will range from $85,000 to more than $150,000, the developer said. Building is expected to begin early this fall.

Other recent developments in commercial realty in the Washington metropolitan area:

*Construction has begun on Continental Federal Savings Bank's new 80,000-square-foot administration and operations center in the Dulles Business Park in western Fairfax County.

The center will house all of the bank's data processing and operations activities, and is designed to provide additional space for administrative functions.

More than 150 employes will relocate to the new facility, which is scheduled to be completed late next year.

*The following tenants have signed leases at 1615 L St. NW, a joint venture of The Beacon Cos. and Metropolitan Life Insurance Co.: Newman and Holtzinger P.C., 37,649 square feet; Tucker Flyer Sanger and Lewis, 23,836 square feet, and Blue Cross and Blue Shield Association, 30,795 square feet. Finally, Cushman Darby and Cushman, patent attorneys, has leased the entire 12th floor, which has 41,244 square feet.

*Rubloff Inc. announced the following leasing transactions: The law firm of Reynolds and Mundy has leased 5,283 square feet at the Madison Office Building at 1155 15th St. NW; Organizational Dynamics Inc. a management consulting firm, has leased 13,641 square feet at 2550 M St. NW; and The Equitable Life Assurance Society has leased 16,231 square feet from Science Applications International Corp. at 3 Choke Cherry Rd. in Rockville.

*Black, Manafort Stone and Kelly, a Washington public affairs firm, has leased 16,000 square feet at Harbor Center in Old Town Alexandria, the Peter N. G. Schwartz Cos. has announced.