The Prince William County Board of Supervisors last week approved a requirement that developers post bonds for private improvements that they have promised to potential buyers.

Under existing policy, a developer only had to carry insurance on public facilities he promised to provide, such as roads, water and sewer systems. Under the new plan, improvements such as swimming pools and playgrounds must be insured by performance or surety bonds. A surety bond guarantees that the work will be finished even if a builder defaults.

Developers argued that the policy would raise housing costs significantly by raising the cost of their insurance. But, according to development administration director Marty Crahan, the average cost of a new home in Prince William County -- $78,600 -- may increase less than .5 percent, or less than $400.

According to the supervisors, the change was made to protect homeowners from contractors who renege on promised improvements.

"We just want you to do what you said you would do," Supervisor John Jenkins told representatives of the Northern Virginia and the county builders associations.

The representatives asked that zoning administrator Michael Congleton be given the sole power to decide whether or not proposed improvements be bonded. "Ninety-nine percent of us shouldn't be punished for what 1 percent of us do," said Tony Ahuja, a spokesman for the Northern Virginia Builders Association.

In addition, the amended policy will require bonding companies to be rated at least A-15 -- the 16th highest of 60 possible scores on the trade industry's rating system. If the rating falls below A-15 during the life of the project, the developer will be required to obtain bonds from another insurance company.

That change was made, the board said, because of two subdivisions that were left unfinished within the last year when the contractor and the insurance company both declared bankruptcy. This change will protect the public from unstable bonding companies when the developers default on a project, the board said.

Other changes made in the county's bonding policy last week were mandated by the General Assembly this year. Designed to standardize bonding procedures statewide, the new law implemented by the board last week allows three bond reductions during the life of the project, instead of the single deduction allowed under the new law. The change also reduces the amount of money that can be held back until a project is completed from 25 percent of the bond's value to 20 percent.

Crahan said the demands on staff time, which will be increased by the release provisions of the new law, will require a new three-man division in his department. The new law says staff must respond to bond release requests within 30 days. "I will make a formal recommendation to the board within the month to allow us to hire three new people," he said.

In other business, the board unanimously approved a measure that will double the fines of persons found guilty of illegally parking in spaces for the handicapped.

The parking ordinance amendments will raise the minimum fine from $25 to $50 and the maximum fine from $50 to $100.

The amendment will also require that parking spots for the handicapped be made evident by signs above ground rather than with paint on the pavement.

Although the measure had the support of a group of handicapped citizens and disabled veterans, Police Chief George Owen told the board that some police officers have refused to issue tickets to motorists that were unaware they were parking in spaces for the handicapped because the markings were not clear.

"Without the signs, the fines are useless," he said. The amendments bring the county into compliance with a state mandate that requires spaces for the handicapped to be marked by above-ground signs.

The county cannot force a business to provide spaces for the handicapped; such provisions are voluntary. According to County Deputy Attorney Stephen MacIsaac, the details of enforcement "haven't been hammered out yet."

Meanwhile a lot of violators "have slipped through the cracks." According to Tom Meagher, chief of the county's benefit program for the handicapped, more than 390 residents qualify for benefits for the disabled, with another 100 listed as temporarily disabled.