Prince William County planners have recommended the county planning commission reject a proposed subdivision because the fast-growing county simply cannot provide enough roads or schools for it.

"In a way, this is a historic first here," county planner Roger Snyder said last week. "It raises the question: must development depend on the preexistence of support services" or must the county provide those services whenever a developer wants to build.

The subdivision proposed by developer Charles R. Ubelhart calls for 417 small single-family houses and town homes on 112.7 acres sandwiched between the Montclair and Dale City communities.

Planners say the proposed subdivision would generate as many as 4,170 cars daily on Cardinal Drive, the small two-lane state road that runs through the tract, plus 300 or so students.

"The basic problem is that Cardinal Drive is already overtaxed with residents from Montclair, and the schools in the area are beyond their capacity as it is," Snyder said.

The planning commission last September rejected an earlier version of the Ubelhart development. Under the new proposal, Ubelhart is offering to phase in development through 1990 so the county has time to build more schools and to improve and to widen roads. The commission is scheduled to hear the revised proposal next Wednesday.

"Our argument is that the county must have a firm commitment" that funds to provide the new services for the development will be available, he said. "We cannot allow this development and take the chance that somewhere the money can be found to build a new school or widen Cardinal Drive."

The decision to recommend denial of the application has raised some touchy legal questions as well.

The Ubelhart land is zoned for agricultural use, but the developer is asking that it be changed to a residential zone that would allow town houses and single-family houses on one-third-acre lots.

The proposed zoning change is sanctioned by the county master plan, updated six months ago. But the master plan has a clause that allows zoning changes only if the county can support the change with fire, police, roads and schools.

"We realize legally we cannot absolutely deny all development for that property," Snyder said. "But we feel we have reason to deny all development at this time."

County attorney John Foote said Prince William will have a good legal case if Ubelhart decides to appeal. State appeals courts have been more lenient to local governments than to developers recently, he said.

"Cases coming down in the last year or two have been on the side of the local jurisdictions," he said. "Courts are realizing that local govenments should have more say on planning issues."

Neither Ubelhart nor his attorney could be reached for comment last week.

The county probably will allow residential development on Ubelhart's land sometime in the future, Snyder said. He said officials already have applied for state funds to widen Cardinal Drive and the School Board has included a new high school in the western end of the county, near the proposed subdivision, in its long range capital plans.

"It is just a matter of time," Snyder said. "But we need more time."