The Loudoun County Board of Supervisors yesterday narrowly approved a zoning change that will allow Eden Associates to build a 314-unit subdivision next to Countryside. The vote was 5 to 4.

Eden Associates, a subsidiary of Milestone Communities of Reston (formerly of McLean), plans to build its development on 47.7 acres north of Route 7 near Algonkian Parkway. The project includes 290 town houses or apartments and 24 single-family homes. Nineteen apartments and three single-family houses will be made available under the county's affordable housing program--the apartments for rent and houses for sale.

The county Planning Commission had recommended approval of the two types of zoning--planned development housing and town house/multifamily residential--needed to build the subdivision. Plans call for nearly seven units per acre. That is well within the required six to 10 houses per acre established in the eastern Loudoun area management plan but denser than the dominant single-family homes and town houses in neighboring communities.

Supervisors who supported the development said it might be the best that could be hoped for at that site. Chairman Dale Polen Myers (R-At Large), who on Tuesday lost her reelection bid to be chairman, said that denying Eden's zoning request would not prevent another developer from proposing a different project with the same or greater density as Eden's plan.

"We could still be looking at town houses back there," Myers said. "Are you really creating a better situation?"

In exchange for the supervisors' approval of the development, Eden will give the county 15.1 acres of right of way needed to extend Algonkian Parkway south of Route 7 and construct sections of the cloverleaf interchange just west of Countryside that eventually will connect Route 7 with uncompleted Atlantic Boulevard.

Len Forkas, president of Milestone Communities, called yesterday's action an "an incredible win-win for everybody."

"The county wins because the interchange can go forward on schedule and on target," Forkas said. "The community wins because they're going to get a connection over to the shopping center, relieving Countryside Boulevard of traffic."

Supervisor Lawrence S. Beerman II (R-Dulles), who made the motion to approve the zoning, said finishing the interchange at Algonkian and Route 7 would help traffic flow smoothly. "We shouldn't leave that undone," he said.

Supervisors who voted against the rezoning said the project will create "nightmare" congestion in traffic and housing.

Some supervisors said they did not like the notion that one intersection--Algonkian Parkway at Route 7--eventually will serve as the conduit to the area's main highways from the Eden development as well as from parts of Countryside, a 20-year-old community with 5,600 residents.

"I think we can do much better on the density," said Supervisor Scott K. York (R-Sterling), the slow-growth advocate who won Tuesday's election for board chairman. York said he had wanted to vote on the Eden proposal a month ago. Instead, the developer requested--and received--a one-month delay to fine-tune the placement of the right of way for the extension of Algonkian Parkway.

Supervisor David G. McWatters (R-Broad Run) said yesterday that he is concerned that construction of a new subdivision in the area could lead to traffic tie-ups.

"I've talked to the people who live down there and they don't want this," McWatters said. "There are going to be 2,500 vehicles a day going down Countryside Boulevard. Just what we need. . . . This seems to me it's adding to the transportation nightmare. When are we going to learn?"

McWatters said that he is concerned that people living in Eden's 24 single-family houses would not want to live next to apartment buildings. McWatters suggested that the developer "scratch" the single-family units "since you don't want them anyway" and use that land for an open-space buffer.

Lawyer Robert M. Gordon, who represented Eden in its rezoning application, said the single-family houses would not be abandoned.

"It is our plan to build the multifamily first--and it's a high-quality apartment complex--and it's our risk, which we don't believe it's going to be, to build the single-family next to that," Gordon said.

Many residents of surrounding communities said in public hearings last summer that they expected to live in an area of predominantly single-family homes and opposed the character of the Eden development. But others expressed concern about what might be built on the property instead.

"The residents of our community feel that this is as good a project as we're going to be able to get on this property," said John Stevens, president of the Broad Run Farms Civic Association, a subdivision with 300 single-family homes that abuts the Eden property. "We feel that turning away this development is playing with fire and could let a different one come in under a different board."

Forkas, of Milestone Communities, said that he expects that the first apartment buildings will be open in about a year.