Residents near the site where a developer wants to build a 23-story apartment and retail complex in Ballston say the building will tower over its neighbors and increase congestion in the already dense Arlington neighborhood.

The complex, proposed for the southeast corner of Fairfax Drive and North Vermont Street, would be a tower of steel and glass amid a cluster of brick buildings. Plans call for it to have 237 residential units and, on the ground level, about 9,200 square feet of retail space, officials said.

Neighbors say the development will add to the daily traffic headaches of the 1,000 residents of the small block, which is already home to five residential and office buildings, said Glenn Elliott, president of the Ballston Smart Growth Alliance, a group that represents the residents.

"We don't oppose the development of the site," said Elliott, a resident of The Continental at Ballston, a 411-unit condominium high-rise adjacent to the site of the proposed 23-story building. "Our issue is the direct effect it will have on the area, with more congestion and overpopulation. It's important for us that the overall size be kept down."

Some parts of the proposal are also being opposed by a neighboring senior center.

The Ballston Smart Growth Alliance challenged the building plans at two meetings last month and presented the county Planning Commission with a 10-page report proposing several changes, including eliminating all but three surface parking lots on the site, creating an underground parking garage, re-routing traffic from a narrow alley that serves pedestrian and vehicular traffic from the existing buildings to a different side of the new building, and limiting the building's height.

The 21-story Continental, which opened in November 2003 at 851 N. Glebe Rd., sits among a cluster of high-rise buildings in the rapidly developing Ballston community, part of the Rosslyn-Ballston corridor that has become a focal point for development in Arlington.

The Jefferson apartments, a complex for seniors, shares an alley with the condo residents. Nearby are two office buildings -- the 12-story, 28,618-square-foot Arlington Gateway and the Ellipse, which houses the Ellipse Arts Center among its tenants -- and the National Rural Electric Cooperative Association.

In addition, a 336-room Westin Hotel is being built across the street.

"We have many concerns," Elliott said. "It's already highly populated for the space, with very narrow alleyways that will only get worse."

But county officials said the site plans, which call for the development of 6.21 acres -- 5.57 of which have already been approved -- are consistent with the county's planned density for Ballston.

"The fact that it's tall is a problem that other high-rise tenants have, but they have to realize that it is compliant with the overall plan for the area," said Terry Savela, vice-chair of the county's Planning Commission.

The proposed building -- referred to as "The Fairmount" because of the existing five-story structure by that name at the site -- will bring "architectural relief to the area" by virtue of its steel and glass design, Savela said. Its construction also offers the county a major bonus: A new west-side entrance for the Ballston Metro station. The developer, The JBG Companies, agreed to build the Metro entrance in exchange for "bonus density" -- additional square footage.

"That entrance has been desired for a long time," Savela said, adding, "And it will really help the property values in that area."

As important as the Metro station is to the area's residents, Elliott said, the group opposes the county's bonus density deal with The JBG Companies.

Residents are not opposed to the additional space but believe the deal should cover only the company's estimated $8 million cost for the Metro entrance and should not be used as leverage to build a 23-story tower, Elliott said. Residents also have suggested that the company use the additional space to create larger residential units in a shorter building or transfer the space allowance to one of JBG's other projects in the area. Among them is the Bob Peck Chevrolet dealership that JBG plans to build nearby.

"It gives us nightmares just thinking about it," Elliot said, adding that many residents of the Continental paid a premium to have a great view from their condos and that a 23-story building next door would ruin that.

Ken Finkelstein, a partner at The JBG Companies, said company executives are "taking into consideration as best we can the concerns that people . . . have expressed about the projects."

He said he met several days ago with two representatives from the Continental and that a dialogue between the groups continues. Still, Finkelstein said, JBG is "doing what is within the framework and zoning regulations" mandated by the county.

Savela said county officials this week were examining the residents' challenges and studying the project's blueprints.

"We know there's a concern that the county is so committed to the new Metro entrance that all other concerns that have been raised are being ignored, and that can't be further from the truth," she said. "Residents have been so thoughtful, and that has really caused everyone to be that much more thoughtful in their review of this plan and in working out the details. The community's involvement has really improved this project."

Residents will be able to share their concerns with county officials at public meetings next month, including one Sept. 1, sponsored by the county traffic commission; Sept. 6 with the Planning Commission; and Sept. 17 before the Arlington County Board.