Developers could be required to replace more than 500 Arlington garden apartments likely to be demolished to make way for high-rise development, under a new plan to preserve the county's low-cost housing.

The plan, viewed by officials as a potential breakthrough in Arlington's efforts to preserve its dwindling supply of housing that blue-collar workers, recent immigrants and the elderly can afford, would require developers of certain tracts -- mostly along Metro's Orange Line corridor -- to replace any units they destroy during redevelopment.

County Board members, who would decide which tracts would be affected, will consider the plan at their Nov. 17 meeting.

But they already have indicated that they support the idea, which county staff members proposed this year after the General Assembly passed legislation allowing counties to use land-use plans to preserve affordable housing.

"It could be a strong legal tool to give us more strength in dealing with developers and reaching our affordable housing goals," County Board Chairman Albert C. Eisenberg said.

Some residents, however, say the county should work harder to preserve, rather than replace, existing garden apartments. They say the high-rises that have sprouted along the Rosslyn-Ballston Metro corridor in Arlington have brought unwanted traffic and crime into surrounding neighborhoods.

"This plan assures the destruction of existing affordable housing," said resident Bernard H. Berne, who lives in the Ballston-Virginia Square area. "Everybody's for affordable housing, but we should look at what we already have. We don't want one high-rise after another."

The new plan, devised by County Attorney Charles G. Flinn and county planners, was prompted by a developer's plans to destroy Pollard Gardens, a 40-year-old, 124-unit complex in the Ballston-Virginia Square Metro corridor.

In an effort to save their homes, Pollard Gardens residents urged the County Board to change Arlington's development guidelines to prevent high-rise development on the site, where apartments rent for $550 to $650 a month.

But board members last week said such a change would reverse years of planning for development along Metro's Orange Line.

Instead, board members turned to the new plan, which would allow the county to create what officials call "affordable housing redevelopment districts" on land that is in the Metro corridor but zoned for low-rise residences.

Arlington housing activist Victoria Luna said that creating affordable housing districts may be the best way to retain low-cost housing in development's path.

"It's the first time we can attach our desire to save affordable housing to law," Luna said. "Up to this point we've just had policies; this goes well beyond that."

Reaction to the new strategy among developers has been mixed; most say they want more information about what would be required of them.

Eisenberg and other Arlington officials say preserving affordable housing is a top priority in the county, where the average apartment rent is now about $700, 42 percent higher than a decade ago.

Nearly 10,000 units with below-average rents have been destroyed or undergone renovations since 1980, county officials say, and there are about 1,800 households in Arlington on a waiting list for rent assistance.

Planning officials from other area jurisdictions say they might consider following Arlington's example.

"That sounds like something that would be attractive," said Fred Selden, a planner in Fairfax County, which like Arlington has allowed developers to build larger projects in return for construction of low-cost housing.