A Maryland home builder has purchased 460 acres of rolling hills, woods and farmland west of Dulles International Airport, where the company will be able to build as many as 256 houses.

Winchester Homes Inc. recently paid $9.3 million for Lenah Farm, which is south of Route 50 and east of Route 15 and is now used to grow corn and soybeans, according to a member of the partnership that sold the land.

Winchester officials did not return telephone calls this week. However, several people familiar with the company's plans said it would start building upscale houses in the coming months and also would bring in additional home builders.

Construction of 256 houses would require no special approval from county supervisors because of the land's zoning designation. The previous owners of the land, Lenah Farm L.P., already received permission for a single-family housing development.

Development plans call for housing clustered on lots that are at least three-quarters of an acre and preserve remaining land as open space, said Richard Wolff, executive vice president of Geo. H. Rucker Realty in McLean, one of the partners in Lenah Farm L.P.

Supervisor James G. Burton (I-Mercer) said the development would increase the need to build schools and roads in a county that is struggling to cope with widespread development.

"The overall size of it--it's very bothersome," Burton said. "It's a lot more houses with more schoolchildren. It's going to increase the pressure even more."

County planners also say they are increasingly alarmed about a flood of development proposals for land near the Lenah Farm property, in an area that lacks roads, schools and other facilities.

Six rezoning requests are pending for the Dulles South area, and developers of 11 additional projects have held preliminary discussions with county officials. County officials said that if all of the projects come to fruition, they will add 5,000 houses to the area.

"It's a classic situation where there is very little infrastructure there now, and so with any new development that doesn't pay its way, you'll immediately be working at a deficit and continue at a deficit," said Julie Pastor, Loudoun's director of planning.

Pastor expressed concern that the amount of money developers would be expected to contribute for schools and other facilities would not come close to covering the costs. Planning officials have alerted the county's Planning Commission about the spate of proposals and urged its members to consider their overall impact.