The Richmond, Fredericksburg and Potomac Railroad Co. and Savage/Fogerty Cos. Inc. have announced the formation of a joint venture to develop a 38-acre site, owned by RF&P, located between the Potomac Yard and the George Washington Memorial Parkway in Alexandria.

The partners plan to develop a mixed-use project containing residential, retail, office and hotel space. An extensive amount of landscaping also is planned.

A parkway interchange, access to which has been approved by the Department of the Interior, likely will be constructed during the initial phase of the project, which is scheduled to begin in the next two or three years.

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

*Smithy Braedon has announced the following leasing transactions: Capital Systems Inc., a computer analysis firm, has leased 24,212 square feet at 4700 King St., Alexandria; George Washington University has leased 16,000 square feet at 515 22nd St. NW; Analysis and Technology Inc. has leased 15,929 square feet at Park Center II, 4401 Ford Ave., Alexandria; Cassidy Associates, a legislative consulting firm, has leased 10,433 square feet at 655 15th St. NW; The American Trading Real Estate Co. has leased 8,634 square feet at 1803 Research Blvd., Rockville; Administration Associates has leased 6,177 square feet at 734 15th St. NW.

*Diamond Paper Corp., a distributor of copying, computer, word-processing and office supplies, has announced plans to relocate from Fairfax to Loudoun County, where the company has broken ground for a 44,000-square-foot distribution center.

The development is to take place on six acres of land located at the corner of Church Street and Route 637 in Loudoun. Completion of the new facility, which is being financed by county-approved industrial revenue bonds, is expected by next summer.

*Cushman and Wakefield has announced the following leasing transactions: The General Services Administration has leased 22,000 square feet at 1800 North Kent St., Arlington, from Rosslyn Plaza East Associates Ltd. for $2 million; Bell Atlantic Management Services has signed a lease for 5,600 square feet at 1133 20th St. NW for $1.8 million; American Arab Affairs Council has leased 2,250 square feet at 1730 M St. NW; Ogilvy and Mather, a public relations firm, has leased 1,600 square feet at 1901 L St. NW.