The Arlington County Board last night unanimously approved a request to operate a group home in the Nauck area for six physically disabled adults and a staff member after the developer agreed to some concessions sought by the home's future neighbors.

Many residents of the South Arlington community, which has a large black population, had opposed the proposal by Cheshire Homes to build a group home at 1911 S. Nelson St. when the issue first came before the board Nov. 6.

With Board Chairman Stephen H. Detwiler (R) away on vacation at that time, the board's four other members split on the proposal. The two Republicans favored it and the two Democrats opposed it.

Last night, both the residents and the Cheshire Homes representatives had reached a compromise involving building the house farther back on its lot than originally planned, changing the main entrance and agreeing to a landscaping design.

The Nauck residents said that, while they wanted to help disabled persons, they feared the already congested site at South Nelson Street and Walter Reed Drive would face additional traffic and parking problems.

John D. Perkins, Cheshire's lawyer, said the firm was willing to move the access roads to Walter Reed Drive to alleviate traffic on the residential South Nelson Street.

The vacant 12,245-square-foot lot is to be purchased by Cheshire from the county for $32,000 if the company can secure federal funds to build and maintain it, county officials said yesterday.

In other action, the board approved 3 to 2 along party lines a request from the Evans Co. for a higher density zoning to allow construction of 8- and 10-story buildings at 3801 North Fairfax Dr. near the Virginia Square Metro stop.