For the second time in the past year, the U.S. Department of Housing and Urban Development is threatening to cut federal money to Fairfax County for delaying construction of a controversial public housing project.

The county could lose $3.8 million in federal grant money, which in the past has paid for storm drainage systems, road improvements and home improvement loans. HUD said it will withhold the funds unless the Board of Supervisors can justify within two weeks its recent decision to impose a 90-day delay on construction of Rolling Roads Estates, a 100-unit development in the Springfield area for low and moderate-income families.

Thomas R. Hobbs, director of the Washington are HUD office, said that the board's "deliberate delaying" of the housing project has forced HUD to wonder "what kind of precedent is being established in the county for future public housing."

Reacting to Hobbs' threat, Board of Supervisors Chairman J. F. Herrity said yesterday that he plans to ask the board to sue HUD "for usurping county authority." Herrity said "it was about time the county started fighting back."

Board member Marie B. Travesky (R-Springfield), who has been a staunch opponent of the Rolling Road project, said Herrity's fighting words "make good press but are totally unrealistic."

The supervisors voted April 17 to delay approval of a site plan for Rolling Road for 90 days to await the outcome of a lawsuit filed by Herrity and two Springfield rsidents against the county planning commission. The suit asks the County Circuit Court to order the commission to review the Rolling Road project as a public facility. Such a review would force public hearing and could possibly stop the project.

The supervisors have been advised by the county attorney and a Virginia assistant attorney general that Rolling Road, although funded by federal money, cannot be considered a public facility and that the planning commission has no right to review the project. Construction of the Pittsburgh, was to have begun this spring.

"I certainly want an explanation (of why the board) would stop the functioning of government because of a question in a lawsuit," Hobbs said. He said the board's decision to ignore its own attorney and delay the project makes him believe "it will be very difficult for the county to meet its public housing goals."

HUD has authority to withhold the $3.8 million in

Community Development Block money if the agency judges the county to be unreasonably delaying public housing goals. HUD last threatened the supervisors with a cutoff funds in November when they voted against construction of the Rolling Road project. The board rescinded its objections a week later.

Herrity, Travesky and some Springfield residents have objected to the housing project, arguing that it "is in the middle of nowhere" and would bring unneeded public housing to an area that already has its share of such units.Herrity said yesterday that the planned project, combined with other existing projects, would bring about 500 low-income housing units to Springfield and "create a ghetto."

Supporters of the project, including the county's Housing and Community Development Agency, say the project will neither affect property values nor overload Springfield with public housing.