Plans for the long-awaited Route 234 bypass around Manassas have cleared several hurdles and construction could begin on the project as early as fall 1991, proponents said.

Although the four-lane highway has been on Virginia Department of Transportation plans for years, it probably will not be built until the next century unless local funding comes through. So local landowners are stepping in to pay for the 9 1/2-mile southern half of the road, from Interstate 66 south to Route 234.

About 15 property owners are negotiating with Prince William officials to pay additional property taxes to get the road built. Last week they submitted a new draft of their petition to set up a special taxing district, and their attorney, Curtis M. Coward, said he expects to work out the details by late September.

"I would hope we can go out to bid {for construction firms} in December," Coward said.

County officials and the landowners have agreed on a 20 cents per $100 of assessed value surcharge for the next 30 years. But they are continuing to negotiate on how densely the landowners will be permitted to develop their land while the taxing district exists.

The only existing transportation taxing district in Virginia -- enacted by Fairfax and Loudoun Counties to pay to widen Route 28 -- became mired in controversy last spring when Fairfax rezoned some land in the district to limit development. The General Assembly reversed the county's action.

Taking a clue from the Fairfax experience, the Route 234 landowners are seeking to limit the county's zoning power over their land for 20 years. County officials, meanwhile, would prefer to bind themselves for a shorter time and also set maximum development limits in the agreement, said County Attorney Sharon Pandak.

The taxing district money would be used to pay off $95 million in bonds issued by the Commonwealth Transportation Board. County officials expect the extra tax money will cover 75 percent of the debt, with the rest of the money coming from Prince William's state highway allocation.

Transportation Department engineers have also solved the thorny issues surrounding the new road's interchanges with Route 28 and I-66.

The Route 28 interchange would be located on land owned by Manassas, and city officials at first were reluctant to give up their property for a road few of their citizens would use.

The city and county recently agreed on a design for a cloverleaf that would consume only 20 acres, rather than the 60-acre plan first put forward.

"We have agreed on a concept the city can live with," said Assistant City Manager Clyde D. Wimmer.

The I-66 interchange has also been controversial. The original design put the cloverleaf just west of Pageland Road, but Congress made that location impossible when it added the land to the Manassas National Battlefield Park in 1988 to protect the park from development.

Transportation Department engineers redesigned the road, moving the ramps west of the new parkland, said Prince William Public Works Director Robert W. Wilson.

County officials are also seeking federal funds to pay for the I-66 interchange, which is expected to cost $10 million.

Rep. D. French Slaughter Jr. (R-Va.), who represents the area, is attempting to use part of the $30 million Congress authorized in 1988 for road improvements around the Manassas Battlefield for the interchange.

"Budget stuff is so tight that we need a line-item appropriation, and it's difficult to get," said Slaughter's spokesman, Carter Cornick.