Fairfax County Supervisors, fearing another massive pipeline rupture in Northern Virginia, yesterday called for inspection of a transcontinental fuel line that crosses the county.

County board members, troubled by reports that pipeline corrosion contributed to the March 6 accidents that polluted two rivers, called for safety checks of the 17-year-old pipeline that supplies much of metropolitan Washington's gasoline and fuel oil.

"What we don't want is another break or explosion" that would damage the water supply and citizens, said Supervisor Martha Pennino. "Our constituents are holding us responsible."

Pennino and other board members pushed for an inspection of the pipeline after hearing a report on the March accidents from a representative of the firm that built and installed it.

Harold Melendy, representing the Colonial Pipeline Co., told the board that both human error and pipeline corrosion combined in the ruptures, which threatened the water supplies of nearly 700,000 Virginians.

The breaks were caused, he said, by an operator in the firm's Atlanta control center who failed to shut down the pipeline after an unexplained pumping station failure in northern Maryland.

But Melendy also assured the board that the company had no reason to believe that any sections of the 32-inch pipeline need replacement, even at road crossings and intersections where, he said, pipe stress is the most severe.

"We do not at this time anticipate going back and replacing each and every road crossing section," he said. He added that Colonial had reduced pressure in the pipeline until permanent repairs are made to the damaged sections near Manassas and Fredericksburg.

The company has also sent sections of the ruptured line to an Ohio laboratory for closer examination.

While pressing for details on the ruptures, board members also quizzed Melendy about the firm's plans for installing a new pipeline in the county. He told the supervisors that Colonial will be installing extra-thick pipe near developed areas and building sites and will also use reinforced material around potential pollution spots, such as streams.

Though the company has made personnel changes and altered its operator training procedures, Melendy said he could offer no guaranteed safeguard against future human-caused problems.

"There really isn't any pipeline that can operate without human involvement, but we've made changes we feel will improve the quality of human involvement," he said.

Melendy also cautioned against thinking of the pipeline as "old." He said there were some pipelines in operation around the nation that are 40 years old and were installed "bare," without any protection against pipe erosion.

The pipeline crossing Fairfax Melendy said, is "still in as good a condition as when it was first put in."

Board chairman John F. Herrity praised Melendy and the Colonial firm for appearing at the supervisors meeting to give the report and answer questions. He said the company's response was far better than that of the federal Office of Pipeline Safety, which Herrity complained had refused to attend the county meeting.