Fairfax County is facing a record 292 challenges to its long-range comprehensive land-use plan this year.

Developers, lawyers, residents and members of the county's own board of supervisors and planning commission are asking for sweeping changes in land use in the growing county as part of the 1985 annual review of the land plan.

The magnitude of many of the proposed changes, the number of proposals and the actual wording of some of the challenges are creating major headaches for county officials.

The proposals cover sites ranging in size from a single building lot to tracts of more than 250 acres.

Because this is a so-called "third year" in Fairfax County's planning cycle, each of the 292 proposals will have to be heard by the planning commission. Its recommendations on each will be passed on to the board of supervisors for action during the next seven months.

In the years between "third years," applicants for changes in the land plan must prove a specific emergency need, show a major change in nearby land use or meet other strict criteria in order to win consideration.

"We will hold public hearings on each of these. That comes to more than 29 hours if you limit the hearings to 10 minutes each," said George Lilly, the congenial chairman of the planning commission who knows that each of those hearings will run much longer than 10 minutes.

"This is a record number," said Bill Keith, a planning staff member faced with a mountain of paperwork and research time generated by the applications. "The previous high was 180. This is a monumental task."

Lilly had been troubled because county law does not require the posting of signs on land proposed for plan amendment changes in the way it requires posting for land which is the subject of rezoning applications.

However, the number of applications has sparked the board of supervisors to vote to have signs put up on sites involved this year to notify residents about proposed changes and public hearing dates.

The county will have to absorb the total cost of posting the sites, because it does not require a filing fee with proposed plan amendments.

Some county officials are worried that citizens of the booming county will not understand the difference between the plan amendment process and an actual rezoning, because the county is so mobile.

Chairman Lilly said that anything approved as a plan change is simply a change in the land-use designation, not a rezoning.

"This is hard to explain to a lot of people," said one planning staff member.

The distinction is that while the land-use plan provides a map for future uses, zoning defines what is currently allowed.

Land in undeveloped areas of the county is often zoned for much less intensive use than envisioned by the plan and is taxed at the lower use.

Then, when the owner or developer feels the market is ready, he seeks a zoning change.

At that point, issues such as road improvements, site plans, heights and the like are considered.

Many of the applications themselves contribute to the confusion.

A survey of proposals filed shows that many are several pages long and spell out specifics of a possible project and all its merits just as a rezoning application would do.

Such language is misleading, Lilly explained.

"Amendments are not supposed to address a rezoning. Too many of the proposals this year are being used as a guise for a rezoning," Lilly said. "Too many read like zoning applications."

At the same time, many of the applications fail to deal with the real issue -- whether or not the use should be changed from one particular category to another, such as residential to commercial.

Promises made about what would be built on a particular site by an applicant if the amendment is approved are not binding, because it is not a rezoning action, officials cautioned.

"If a public hearing begins to dwell on the merits of a particular application, rather than on land-use issues, it can be a problem," Lilly said. "It is hard to separate the two. It falls into the lap of whoever is presiding to make sure that those applications that seem to rise to specifics of a project are limited to discussions of land use during the hearings," Lilly said.

That will be his job when the applications get before the commission.

But a lot of the talk about a specific proposal may take place before the scheduled public hearing.

Many of those proposing some of the more controversial changes this year have already been meeting with members of neighborhood associations in many parts of the county in efforts to explain the merits of their proposal.

"It is possible for some of the advance work being done now to take the steam out of some of the opposition unless the public understands that the plan amendment change is just the first step," explained one lawyer who asked not to be identified because he does a lot of land use work in the county.

Once a plan amendment is approved, an applicant can file for a rezoning.

Only action on a specific zoning application by the board of supervisors can approve or kill a specific project for a specific site.

"There is a latent danger in treating a plan amendment as a rezoning," Lilly said.

County staff members warn that the words of a would-be developer or property owner can change drastically from the time a plan amendment is acted on and a rezoning application is filed.

Many of those proposing changes are contract-owners of sites involved. Others own and live on the land they want to change.

Still others are major developers; some are speculators.

"You don't even have to own the land or have a contract on it," Lilly explained.

"Anybody can nominate anything they want to," he said. "You can nominate my back yard. I think this is a weakness in the system."

Fairfax publishes a tabloid listing of plan amendments and mails copies to county residents.

"How many people do you think are going to sit down and wade through 292 proposals?" asked one lawyer who said he was pleased with the decision by the county to put signs up on the land involved this year.

Meanwhile, citizen task forces are being set up by members of the board of supervisors within planning districts in the county.

Those task forces also will hold public hearings on the proposals and make recommendations.

The planning commission public hearings are scheduled to begin April 17.

The board of supervisors is scheduled to begin work on the proposals in June. The schedule of specific hearings is not yet available.