Federal and Fairfax County officials agreed yesterday on a plan for enforcing construction site safety rules that would bypass what county officials have called inadequate enforcement efforts by the state of Virginia.

Meeting in a closed session, David Rhone, the federal Occupational Safety and Health Administration regional director, and top county staff members tentatively agreed on a plan in which the county's 131 building inspectors would report serious construction safety violations to federal officials for enforcement.

The plan, which still must be aproved by OSHA head Eula Bingham and the Fairfax County Board of Supervisors, is bound to be controversial in light of the county's recent battle with state safety officials over inspection procedures.

Assistant County Attorney Edward E. Rose called the agreement a 'victory for Fairfax County and for construction safety," saying it will allow the county to work around a state inspection system that was "particularly onerous in practice."

By contrast, Rose said, federal officials the county to get this problem resolved."

The agreement follows a county decision to defer the bidding deadline on a $1.4 million storm drainage project after local builders objected strenuously to a county prohibition on bids by contractors guilty of serious safety violations in the last three years.

Rose said Acting County Executive J. Hamilton Lambert, after talking with Rhone, had decided to seek a modification of that prohibition. Under a proposal Lambert will offer to the supervisors on Jan. 28, Rose said, the county would bar only those contractors convicted of willful serious safety violations or violations in which a worker has been killed, or those who fail to abate serious safety violations after being warned by the county.

Officials in Virginia's most rapidly developing county have been crusading to reduce construction accidents in Northern Virginia in the last two years, two of them in Fairfax County.

The county supervisors have complained bitterly that the three inspectors provided by the Virginia Division of Construction Safety in Richmond cannot possibly inspect all the building sites in the booming Northern Virginia area.

Under the tentative agreement reached yestersday, OSHA will assist Fairfax in training the 11 county inspectors to recognize serious safety violations. The county has a particular interest in such violations as those involving excavation work, scaffolding, ladders and railings, Rose said.

When the inspectors detect such violations on job sites, they will be directed to advise an area supervisor. If the problems are not resolved, the inspectors will be told to notify federal OSHA officials, who then may cite the employer for a willful serious violation.

Virginia Attorney General J. Marshall Coleman ruled last year that local inspectors lack the power to enforce construction safety under state regulations. Local officials hope that their agreement with OSHA will permit them to circument that ruling.