The Fairfax County Board of Supervisors unanimously adopted a zoning plan last night that charts how rural Centreville, one of the last large open areas of the county, should proceed with developing 3,000 acres.

The decision, which climaxed a three-year, county-sponsored study on how to regulate growth in the southwestern part of the county, was hailed by Centreville residents as a victory over the development community, which previously had enjoyed great success with the county board.

"We're absolutely ecstatic," declared Richard Korink, a civic leader who led the drive for the county's acceptance of the citizens-backed study. "I never thought we'd get to this point. It restores our faith in the system." Korink characterized as negligible the effect of an amendment to the plan that would increase the number of proposed apartment units on the 3,000-acre site from 2,627 to 3,367. Overall, the amended plan increases the number of residential units planned for the area by about 7 percent.

In accepting the plan, the county ignored a lawsuit filed last week by the Olin Corp., which claims that the zoning blueprint violates the county master plan and prohibits the construction of an office park on its 112-acre site.

In adopting the study, the county rejected the pleas of area developers, including prominent developer John T. (Til) Hazel, to permit high-density office and commercial development in Centreville.

Hazel and other developers with landholdings there angered both the residents and county officials several weeks ago when, just moments before the three-year study was set to be voted upon by the Planning Commission, they filed an alternative plan that downplayed residential construction in favor of office-commercial development.

The commission rejected the developers' proposal and sent it on to the county board, where it created a brief political furor when Supervisor Elaine N. McConnell for a time balked at supporting the citizens' position.

McConnell relented in the face of the overwhelming citizen opposition to her stance and, by the time of last night's meeting, appeared to have made peace with her constituents. McConnell sponsored the resolution accepting the plan.

The plan covers the parcel of land in the area of Rte. 28, Rte. 29, Braddock Road and I-66.