The Fairfax County Board of Supervisors approved plans yesterday for what could become the largest office and commercial complex in the county -- a planning change that could bring the equivalent of three Tysons Corners to an area west of Fairfax City.

The supervisors voted, 8-to-1, to increase the planned density for 5,300 acres at the intersection of Rte. 50 and Interstate 66 near the Fair Oaks Mall to allow up to 17 million square feet of commercial space.

The project, called Fairfax Center, would be what Board Chairman John F. Herrity called an "urban village" of offices, stores, industry, county government agencies, and thousands of homes. The site is sparsely developed, and composed of several large tracts held by a few influential individuals.

The board, in a later action, decided against asking voters this fall to approve a bond issue to build a new county government center in the complex, where it is planned. The supervisors, whose wish to locate the new government building west of Fairfax City first sparked the idea of creating Fairfax Center, decided last night that the referendum ballot is already too crowded with bond requests.

The plan for the Center was described by Herrity as "a new concept that will enable Fairfax County to continue its economic development program and to become a leader in developing commercial and industrial estates, especially high-tech companies. . . I think it's crucial for the future of the county."

Michael S. Horwatt, a lawyer who chaired a county task force on the area, agreed. "This is an investment for the future," he said after the vote.

The supervisors' principal fear in approving the Fairfax Center project was that it will produce nightmarish traffic problems, much like those around Tysons Corner. County officials have said, however, that the rezoning approved yesterday will be a boon to both the landowners and county tax revenues.

In an effort to assure that the county will not be stuck with the cost of building roads in the area once construction begins, the supervisors voted to require that developers pay at least $2.50 per square foot of office space toward the cost of new streets in certain intensively developed areas.

"It was a difficult decision for me to support this proposal," said Providence Supervisor James M. Scott, whose district includes much of Fairfax Center. "We do need desperately some transporation improvements in the area."

The sole dissenting voice on the plan came from Supervisor Audrey Moore, an Annandale Democrat. She cast her vote against the project after most of approximately 20 motions she introduced to tighten control over the development were rejected by the board.

In a memo circulated before yesterday's meeting, Moore said that her suggestions were meant "to protect the county in both the areas of land use and transportation." She also urged that the board delay its decision on the development until it sees what actions are taken by landowners in the Occoquan Basin, which the county board rezoned for more sparse development last week.

The "downzoning" of the Occoquan had originally been linked to the rezoning of Fairfax Center by several supervisors. Moore said she wanted to make certain that the Occoquan action -- a last-gasp move by the county to preserve Fairfax' mostly undeveloped western quadrant -- survived any legal challenge before approving the intense new development. The board, apparently agreeing with Herrity that the two issues could not be legally linked, rejected Moore's motion.

"We just don't have the legal ability to do what she wanted us to do," said Board Vice Chairman Martha V. Pennino, a Centreville Democrat.

Among those who stand to benefit from the increased density planned for Fairfax Center is attorney and developer John (Til) Hazel, who with a partner holds 675 acres in the area valued before the rezoning at $3 million.

Hazel, whose land may one day be the site of a major highway interchange, served on the task force that this spring urged more increased development at Fairfax Center. Hazel's tract is expected to be one of the first in the area to be developed.

In fashioning the bond referendum package last night, the board decided to pass up the proposed government center, slated to cost more than $50 million, because it seemed too large a package to squeeze onto an already crowded bond ballot.

"I just cannot fund a government center and rob from the schools and from the parks and from the libraries," said Mason District Supervisor Thomas M. Davis III.

The county already has more than $150 million in voter-approved but unsold bonds, including bonds for schools, parks and libraries. Last night the board voted to put on this fall's ballot: $25 million for road improvements; $58 million for the county and regional park authorities, and $25 million to continue the development of the Metro system in Fairfax County.