The Fairfax County Board of Supervisors yesterday ordered County Executive J. Hamilton Lambert to investigate last week's's gasoline pipeline rupture in Centreville and approved a zoning change that will permit county residents to have free-standing basketball standards in their front yards.

Also yesterday, the board approved a border change for the Town of Herndon. If the change wins approval from the state, a large commercial and industrial area north of the Dulles Access Road and east of Centreville Road will become part of the town.

In exchange, Herndon would lose a small plot south of the Dulles Access Road and another sliver of largely residential land that is generally east of Sugarland Run and north of Walnut Branch Road.

Supervisor Nancy K. Falck (R-Dranesville), who proposed the boundary change after three years of negotiations, said it would provide Herndon with "millions" in additional town tax revenue while costing the county nothing. The proposed changes now go to the Virginia State Commission on Local Governments for review.

In a briefing on the gasoline spill that forced the evacuation of an elementary school and more than 300 homes in the Singleton's Grove and Sunset Ridge subdivisions in western Fairfax, Lambert said a surveyor has determined that the 32-inch-wide gasoline pipeline, which is owned by Colonial Pipe Line Co. of Atlanta, was buried 35 inches below grade, "well within federal guidelines."

A bulldozer that was leveling ground for a sidewalk punctured the pipe, causing unleaded gasoline to spray 100 feet in the air for about 10 minutes and saturating the ground with thousands of gallons of flammable fuel.

Lambert said yesterday evening that Colonial has agreed to pay all costs associated with the county's evacuation and cleanup efforts. He said there was no preliminary estimate on the cost of the emergency operations.

Lambert said county workers are continuing to monitor the area where the spill occurred. In addition, he said, the county is "reviewing all plans related to Singleton's Grove."

Republican Board Chairman John F. Herrity, who asked for the investigation, requested that the county staff report periodically on its findings.

Supervisor Audrey Moore (D-Annandale), pointing out that an old county staff report identified the pipeline as a potential problem, asked the board to consider a policy of minimizing the construction of new roads over pipelines and providing buffer zones so there would be a "totally undisturbed area" around the lines.

The board's action on basketball goals apparently ends an issue that began when a resident was ordered to remove his goal -- attached to a pole set in concrete -- because it was not permitted by the zoning code. Goals nailed to garages, however, were legal.

The new zoning change permits free-standing basketball standards in front yards, provided that the poles are at least 12 feet from the side property line and 15 feet from the front property line. The amendment states that the hoops cannot be used between 8 p.m. and 8 a.m.

In other matters yesterday, the board:Reappointed six School Board members to two-year terms: Mary E. Collier (Dranesville), Joy Korologos (At Large), Anthony T. Lane (Lee), Frank Francois (At Large), Kohann H. Whitney (Centreville) and Carla Yock (Mason). Received a county staff report repudiating a 1982 report by the Greater Washington Research Council that had predicted that the county would be operating with a $152 million deficit by 1987. The county staff report, requested about four weeks ago by Herrity, said that that research council had made a $225 million error in its projections, based on the county's current positive balance of $18.1 million this year and $54.4 million in tax decreases in the past five years. Endorsed a prioritized list of interstate and primary road improvements in the county to be financed by Virginia Department of Transportation funds available in fiscal 1988.