More than two dozen Fairfax County landowners, ranging from developer-lawyer John T. (Til) Hazel to the Benedictine Society of Virginia, have filed an unprecedented barrage of lawsuits challenging the county's right to control growth in its less developed west.

The lawsuits, affecting several thousand acres, allege that the Fairfax Board of Supervisors illegally violated property rights and reduced potential profits when it limited development to one house per five acres in its western woods and farms.

The supervisors this summer downzoned 38,500 acres in southwest Fairfax in a what they said was an effort to keep pollution out of the Occoquan Reservoir, which provides drinking water to more than 600,000 Northern Virginians.

"It's one of the most irresponsible actions that I've ever seen them do," said attorney Francis A. McDermott, who filed several suits. "I think they're going to get their come-uppance."

McDermott said landowners have invested millions of dollars in engineering, and road and sewer construction, much of which will be lost if they are not allowed to develop one house per acre, as they previouslycould.

Fairfax Supervisor Audrey Moore, a supporter of the growth limits, said the lawsuits represent the most concentrated assault on a county land use decision she has ever seen.

"It's going to take an enormous effort by the county to fight these, just in terms of manpower," Moore said. "They're coming in the windows and the doors. . . It's a very broad-based attack on the county's ability to do things."

Beyond Va. Rte. 123 on the way to the Blue Ridge Mountains, the Occoquan watershed covers 100 square miles of Fairfax, or more than one-quarter of the county. Environmentalists see it as the fast-growing suburb's last chance to preserve significant open space, while developers and builders see it as their last opportunity for significant profits and the county's last chance to provide affordable housing.

The board on July 26 downzoned much of the valley from one-acre to five-acre development, citing a study that predicts the reservoir could turn into a smelly swamp if some action is not taken. At the same time, the supervisors approved intense development in a relatively small, 5,000-acre triangle of the watershed where Route 50 and Interstate 66 come together.

The largest landowners in that triangle and biggest potential beneficiaries from the upzoning were Hazel and his partner Milton V. Peterson, who together have built much of western Fairfax, including Franklin Farm, Fairfax Station and Burke Centre. Hazel is also a successful lawyer who has helped convince Virginia's conservative judges to overturn several previous county attempts to control growth.

Last week Hazel and his partners sued the county, claiming the county's action decreased the value of more than 200 of their unfinished Fairfax Station lots in the general downzoning. Hazel's law firm also led the way in filing more than 20 lawsuits on behalf of other landowners from near Dulles International Airport in the west to the Occoquan River in the south.

Supervisor Moore proposed last summer that the board delay approving the intense development around I-66 until any challenges to the downzoning were resolved in court. "I thought it would give a little incentive to these people who want to profit both ways," she said. Other supervisors, however, said Moore's proposal was illegal.

The lawsuits filed last week and earlier in Fairfax Circuit Court, on behalf of 5-acre tracts and 820-acre expanses, challenge almost every aspect of the board's action. They deny the reservoir is in danger and disagree that the downzoning would be the best way to solve a problem if one existed.

Most of all, the suits complain that landowners who invested thousands--and in some cases millions--of dollars in engineering and site preparation now would be unable to recoup their investments. The owner of one 278-acre tract filed a claim for $2.9 million in what zoning lawyer Marc E. Bettius said were wasted engineering costs and reduced property values.

The Benedictine Society, headquartered in Richmond, was given 253 acres near the intersection of Pleasant Valley and Braddock Roads in 1956 and has been holding onto it for eventual development, according to a lawsuit filed by McDermott, a partner in Hazel, Beckhorn & Hanes. With the new five-acre rule, according to the suit, development "is not economically or practically feasible."

The Benedictine suit, like most of the other challenges, asks the courts to overturn the downzoning and order the supervisors to permit one-acre development. Supervisor Marie Travesky, whose Springfield district includes most of the watershed, said she believes some landowners who have made significant progress toward developing their land should have been exempted from the restrictions.

"I thought we should let them out so the whole thing plan didn't get overturned," Travesky said yesterday, cautioning that she has not had time to study most of the suits. "I suppose there's an opportunity to settle them, that might be another way to save it."

Moore disagreed, saying any exception would weaken the county's position in court. She said the county master plan has called for five-acre zoning since 1975. "It seems to me they were on notice for a long time that this was coming," Moore said.

McDermott said the first full trial of an Occoquan case might come in six to nine months.