Fairfax County agreed last night to let a developer replace a neighborhood of 65 single-family homes at the Vienna Metro station with a massive complex of mid- and high-rise towers that could transform the way people live, commute and work in Washington's largest suburb.

The Board of Supervisors' approval of Pulte Homes' MetroWest project, after three hours of public comment, ended a contentious three-year debate over how the county should find homes for its ever-growing population.

Instead of sprawling cul-de-sacs, MetroWest will cluster offices, stores and 2,250 townhouses, condominiums and apartments south of the Vienna Station, making the project the centerpiece of an effort to concentrate development in dense, urban settings.

It's a vision that's sweeping land-use decisions from Largo to Tysons Corner, where planners and politicians -- to the chagrin of many neighbors -- are accommodating the region's demand for housing with densely packed homes on slivers of land near public transit with the goal of coaxing people from their cars.

MetroWest's many critics have argued that the mini-city will bring too many cars to the congested roads off Interstate 66 and too many riders to the crowded Orange Line. But county leaders said the cluster of 13 buildings on 56 acres will concentrate growth in the only space left in Fairfax, the Metro station's back yard.

The buildings closest to the station will feature retail stores on the ground level, with condominiums, apartments and offices above, tapering to townhouses farther from the station. The complex will be linked by narrow streets designed for pedestrians.

"We've seen people who think this [project] represents runaway growth," said Linda Q. Smyth (D-Providence), whose district includes the site. "In fact, it is just the opposite. This is growth that has been constrained. There is not density creep here."

Smyth criticized what she called a "politicization of the land-use process" during the debate on the project.

The vote late last night was 8 to 1, with Supervisor Michael R. Frey (R-Sully) opposing. Supervisor Gerald W. Hyland (D-Mount Vernon) was absent.

Frey said he could not support the project because too many MetroWest residents will compete with his constituents for space on the county's roads.

"We seem to act as if the people who don't use transit will disappear when they get off the site," he said. "They won't. The people I represent today can't find a parking space at the Metro."

The planning commission backed the project, which will be one of the county's densest developments, earlier this month.

But disappointed civic activists who fought the project's scale said their elected leaders betrayed them.

"I think there's been a breach of trust with the community," said Will Elliott, a neighboring homeowner and founder of FairGrowth, which formed largely to fight for fewer homes in MetroWest. "This is a project that has very little acceptance in the community. This isn't transit-oriented development."

At last night's hearing, critics alternated with supporters, including business leaders and environmental groups. Others said new shops will be a boon to the residential neighborhoods around the Vienna Station, the last at that end of the Orange Line.

"The inescapable and inevitable fact is that we will continue to grow," said William Lecos, president of the Fairfax County Chamber of Commerce. "But the county must grow differently than it has." He called MetroWest "the right project in the right place at the right time, built to the right scale."

But other speakers argued that MetroWest will lack sufficient incentives to encourage its residents to use Metro because the Orange Line cannot ferry them to every job, soccer game or errand. They questioned whether Pulte will build and open enough stores and offices as quickly as homes to discourage residents from driving. And they called on the supervisors to demand more open space from the developer for athletic fields and parks.

Pulte will address some of those concerns with an unusual agreement that it can be fined up to $500,000 if it cannot reduce car use by about half the number of new trips MetroWest is expected to generate.

The builder also agreed to construct more of the up to 300,000 square feet of office space and 100,000 square feet of retail space earlier in the construction process. Pulte pledged $750,000 to lay turf on an athletic field and to improve roads leading in and out of the Metro station. The development also will include 400 condominiums for retirees who, in theory, use their cars less.

But opponents said last night that the efforts fall short.

"You're ignoring the public's pleas for caution," Mark Tipton, a neighboring homeowner, told the supervisors. He called Pulte's pledge to accept fines "an excuse to grant the outrageous density in MetroWest. . . . It's like buying the right to create traffic congestion."

The MetroWest proposal, by its sheer size, generated fierce opposition from neighbors in leafy subdivisions. Town of Vienna officials down the street opposed it from the start.

The debate turned partisan last year, when Rep. Thomas M. Davis III (R-Va.), who lives in Vienna with his wife, state Sen. Jeannemarie Devolites Davis (R-Fairfax), threatened to hold up federal Metro funding if the project was not scaled down.