After five years of peaceful coexistence, the Fairfax County supervisors and the county's powerful building industry are exchanging heated words over a zoning system the developers say amounts to blackmail.

"It's an arrogant power play. I'll be damned if I'll just roll over," huffed ordinarily soft-spoken Democratic Supervisor James M. Scott of the builders' demands the system be haulted.

At issue is the board's practice of requiring developers to "volunteer" to furnish certain amenities such as gutters, noise abatement barriers and dry basement warranties in exchange for favoritable zoning decisions. A similar system in surburban Maryland led a Bethesda car dealer recently to install a nine-hole golf putting course atop his three-story garage.

In a letter to the board, the Northern Virginia Builders Association, the Washington area's largest, has asked for a hearing no later than the week of Nov. 3 to discuss drastic changes in the system. Otherwise, the group threatened, it will seek help from the General Assembly in Richmond.

"I'm amazed," said board vice chairman Martha Pennino. "I feel like they think they're holding a gun to our heads."

"The supervisors have put a piece of zoning," countered prominent zoning attorney Marc E. Bettius. "It's blackmail."

The flare-up is reminiscent of some of the running battles between the board and the builders that occurred in the early 1970s, when the Fairfax legislators, concerned about the country's rapid rate of growth, tried to put tight restrictions on development.Those battles led to a number of courtroom confrontations, all of which the supervisors lost.

The controversy centers on what, under state law, is called conditional zoning. Under such zoning, the developer agrees to "proffer" certain things -- such as land for a park or pathway -- in exchange for being able to build at the density he wants to build.

State law says the proffers are supposed to be offered voluntarily by the developer. But the developers charge athe board has been extracting all sorts of "goodies" by saying, in effect, do as we say or you won't get the zoning you want.

Bettius contends the proffer system is actually a high-powered game "where zoning is bought and sold. The tragedy of the system is, suppose the landowner can't afford a Bettius or Hazel [John T. Hazel Jr., like Bettius is a heavy-hitting zoning attorney]. Suppose it's a little old lady."

State Sen. Joseph V. Gartlan (D-Fairfax), one of the authors of the conditional zoning statute, acknowledges there are "problems and possibly abuses" by the county, based on his conversations with builder representatives and his reading of a study on the subject by the Fairfax County Planning Commission. But Gartland said "I'm trying to avoid" a confrontation in the General Assembly.

Meanwhile, the angry tone of the dispute persists.

"I don't like ultimatums," said supervisor Marie B. Travesky (R-Springfield) whose district has been the site of the heaviest concentration of residential development. "I won't stand for an ultimatum."

Builders' spokesman Robert Johnson denied the letter represented an ultimatum. But he added, "They [the supervisors] have been foot-dragging, and we're not going to let another session of the General Assembly go by."