Merryhill Joint Venture has won Fairfax County's approval of a plan to build 19 luxury town houses around Merryhill, one of the few remaining old homes in central McLean.

Located along Dolley Madison Boulevard, Merryhill is immediately across the street from Salona, the historic home of Democratic State Sen. Clive L. Duval. The Merryhill home must be maintained as a single-family, detached residence, according to plans approved by the Fairfax County Board of Supervisors.

When the proposal for town houses on the small four-acre site surfaced more than a year ago, many McLean residents opposed the development because they feared it would set a precedent for changing adjacent sites from low-density to high-density residential. County planning officials said that is not likely to happen.

The units will cost close to $500,000 each, according to developers.

The project is adjacent to the luxury Madison of McLean town house project where units now sell for more than $350,000.

The Fairfax County Planning Commission has delayed action on a controversial proposed rezoning of 98 acres along the north side of Leesburg Pike, west of Tysons Corner, until July 17.

Dwight Schar, head of NVCompanies, whose subsidiary, NVLand, owns the site, said county planners had asked for additional information on traffic and environmental issues, which prompted his firm's request for a delay.

The rezoning was filed almost a year ago. County officials said it challenges Fairfax County's long-standing policy of banning new commercial development along Leesburg Pike northwest of the Dulles Airport Access Road corridor to the Loudoun County line.

The Virginia Department of Highways and Transportation recently told Fairfax planners that proposed access points along Leesburg Pike would not be acceptable to state highway officials. They said entrances and exits would also have to be provided along Lewinsville Road, a heavily traveled residential street.

The proposal is now scheduled for action by the Board of Supervisors on July 28.

The city of Falls Church wants to try to annex the George Mason school site, which lies just outside the city limits in Fairfax County along Leesburg Pike at Haycock Road.

The school site abuts the West Falls Church Metro station and city officials want the school, which is Falls Church's only intermediate and high school, to be inside the city limits.

There has been talk about the possible redevelopment of the site because of its proximity to the Metro station. Fairfax officials said the site should remain as a school when the county adopted development plans for the West Falls Church station. However, Fairfax officials and Falls Church leaders last year talked about swapping the George Mason site for an abandoned school facility owned by Fairfax County inside the Falls Church city limits.

However, no land swap has been negotiated and Falls Church officials are now starting to talk about annexing the school site.

IN THE BUSINESS . . . The Prince George's County Council has approved more than $10 million in Maryland Economic Development Revenue Bonds for four projects: $6 million for the Allentown Road Associates Limited Partnership for construction of a commercial office building in the 5700 block of Allentown Road; $2 million to CWI Limited Partnership for manufacturing, sales and distribution facilities in the Ammendale Business Campus; $1.3 million for Specialty Retailing Inc. for a leather craft shop and distribution center at Tucker Street and Ewing Road in Beltsville, and $990,000 to Kenneth T. Haley to finance facilities to be leased to businesses . . . Northwest Land Corp. of Washington is building 24 homes costing more than $600,000 apiece as the third phase of Foxhall Crescents, a collection of homes on the site of former vice president Nelson A. Rockefeller's Foxhall Road estate . . . Lois Zambo, a corporate vice president at Julien J. Studley Inc., a commercial leasing broker here, has been named the "top producer of the year" by the Washington Board of Realtors. She negotiated more than $125 million in transactions last year . . . BMW of North America is the first firm to start construction at the Loudoun Tech Center on Rte. 7 near its intersection with Rte. 28 . . . The Dupont Circle Conservancy has presented its first preservation award to the Argyle House at 22nd Street and Massachusetts Avenue NW, because of the careful rebuilding of the mansion after it was nearly destroyed in a September 1984 fire . . . Mason Hirst Cos. have broken ground on the third phase of the Cherokee Business Center, an office building complex at the Edsall Road interchange of Shirley Highway . . . The Suburban Maryland Building Association has honored three men as its top residential builders -- Carter Willson of Carter Inc. as the best small builder, Richard Pettit of Richard B. Pettit & Co. Inc. in the medium builder category and Clarence Kettler of Kettler Brothers Inc. in the large builder category . . . Home resale activity in Maryland dropped by 0.1 percent during the first three months of the year compared with 1985, falling from 70,800 sales to 70,700, according to the Maryland Association of Realtors . . . The Virginia Association of Realtors reports that statewide home sales in the first four months of the year were up 44 percent, from 22,335 to 32,224 . . . The Little Rocky Run development in Fairfax has sold 822 homes in the last 1 1/2 years . . . McDevitt & Street Co. has started construction on 1001 30th St. NW, a 52,000-square-foot office building being developed by Trammell Crow Co. . . . Vector Realty Group, since its inception last July, has sold or leased $75 million worth of real estate. Two of the firm's principals, Vernon Knarr and John Kyle, were recent co-recipients of the D.C. Association of Realtors' "top producer of the year" award for commercial sales and co-recipients of the "sales transaction of the year" for the $167 million sale of the Tysons Corner Shopping Center . . . The Gallery Row project, which includes five restored historic facades and spaces for arts uses, has opened along Seventh and D streets NW. . . . The Columbia Historical Society has awarded its Renchard Prize for Historic Preservation to the D.C. Preservation League . . .

PERSONNEL FILE . . . William Keefe, chief of the comprehensive plan branch in the Fairfax County planning office, has resigned to become planning director for the town of Herndon . . . Julien J. Studley has named four new corporate vice presidents -- Patricia A. Terry, Jack M. Schneider, Ken Druskin and Jeffrey Shrago. In addition, the firm has named Paul Chandler, Diane Yochelson, Jeffrey Diamond and Larry E. Walker as vice presidents . . . Carol Ely-Riggle has been appointed vice president of career counseling at the Long & Foster realty firm . . . Randy Glesenkamp has been named administrative vice president for a newly created 13-state region at Empire of America Realty Credit Corp. G. Martin Bonnett Jr. has been appointed divisional vice president for Virginia and surrounding markets.