The Arlington County Board is clearing the way for development of two pieces of land considered key to revitalization of the Ballston area.

With the blessing of nearby residents, the board last week unanimously approved amendments to the county land-use plan that changed the designation of the undeveloped, 10-acre Pocahontas Tract from "service-commercial" to one that would permit mixed-use, medium-density, office-apartment-hotel development.

The board similarly changed the classification of the 2.3-acre Pla-Mor Bowl America site and rezoned the land to medium-density office space. Those actions will allow an office building of up to 12 stories.

The Pocahontas Tract and the bowling alley site are bounded by Fairfax Drive, Glebe Road, Washington Boulevard and I-66. The two are at the future site of a major interchange from I-66 to Fairfax Drive -- an interchange that will serve as the "gateway" to the Rosslyn-Ballston corridor, which is undergoing rapid development around its five Metro stops.

The properties are about a five-minute walk from the Ballston Metro station and the Parkington shopping center, which county officials also hope will be renovated.

Tom Carr, project manager for the Oliver T. Carr Co., which is developing the Pocahontas Tract, said the firm probably will file for a rezoning of the site late next month. Development of the site will be phased in over nearly 10 years, he said.

Although plans are still tentative, Carr said he expects the company will build three office buildings, ranging from 12 to 14 stories, on the southern part of the tract, which abuts the bowling alley site. Nearly 55,000 square feet of retail space is planned for the base of the office towers.

On the northern section of the tract, Carr said, the company's plans tentatively call for 343 residential units in buildings of up to 16 stories.

The Carr Co. and Paul I. Burman, owner of the bowling alley parcel, worked with each other and nearby residents to coordinate their plans so that development would have minimal impact on the surrounding neighborhoods.

County planner Rob Baker said the result is "a neat example of how developers, the (planning) staff and the neighborhood can get together on something and come up with a plan that seems to meet everyone's needs and concerns."