A consulting firm said yesterday that the International Business Machines Corp. plant near Manassas was the source of a chemical that was recently discovered in a well that used to serve a heavily populated area.

In a report to the Prince William Service Authority, the county's water agency, Dunn Geoscience concluded that perchloroethylene found in the Sunnybrook Well No. 7 came from the nearby plant, which uses the chemical on electrical components. Attempts to reach IBM officials for comment were unsuccessful.

The consultant's report, released by county officials, said the chemical "has infiltrated the local ground water system at the IBM facility and appears to have migrated off site in a northerly direction toward the well field."

An official with the Environmental Protection Agency said in January, when the well was closed, that the chemical "is not considered very dangerous" and that evidence that it causes cancer is slim.

The well is located off Rte. 234 (Sudley Road) near the Manassas City line. County spokeswoman Joyce Eaby said yesterday that no decision has been made when the well will be reopened. Residents who relied on the well have been served by 12 unaffected wells.

Eaby said IBM has cooperated with the consultant and service authority, and has agreed to pay up to $200,000 in cleanup costs, which are currently estimated at $144,500. She said she does not believe the county is contemplating any further action against IBM.

"IBM's response to this community problem has been proactive," said Joseph D. Reading, vice chairman of the county Board of Supervisors. "Sharing technical information and its consultants, as well as offering financial assistance, demonstrates this corporation's commitment to act in the best interests of the community."