A Prince George's County judge yesterday ordered a Washington businessman to cease dumping allegedly hazardous wastes at a five-acre site near Fort Washington where Maryland authorities say they have discovered deposits of PCB, oil, hospital refuse, domestic garbage and other materials.

Circuit Judge Albert T. Blackwell issued an interim injunction against Edward E. Thomas, owner of the site on Old Fort Road in southern Prince George's, after the state Department of Health and Mental Hygiene filed suit against Thomas asking that he be fined $200,000 and barred from making unlicensed and illegal disposals.

A hearing on the issue was set for Friday in Circuit Court in Upper Marlboro.

The lawsuit, filed by state Assistant Attorney General James J. Lyko on behalf of the health department, claims that health inspectors repeatedly asked Thomas to cease dumping wastes at the site since last fall. They said he lacked the proper permits for dumping.

Inspector Robert Heiniger said in an affidavit filed with the lawsuit that in addition to such relatively harmless items as rubble, demolition debris and tree stumps, he discovered pools of waste oil, liquid PCB from electrical capacitors and hospital trash.

He said a bulldozer operator at the site told him he had observed at least 60,000 gallons of oil dumped there in recent months.

Thomas, reached at his home in Southeast Washington yesterday, said he has been in the excavation and trash hauling business for 27 years and believes he acted properly. He said he has a sand and gravel mining permit that allows him to fill in excavated areas with refuse and debris as he has done for years.

"I don't think I did the community any harm," he said. The inspectors "are exaggerating the 60,000-gallon oil thing to the nth degree. The only oil I put down was to control the dust, which is not illegal."

As for the PCB, Thomas said unauthorized metal scavengers "plucked the capacitors out of some light fixtures and caused a little bit of PCB liquid to spill. That's all."

Thomas said he believes state inspectors have singled him out for harassment. "There are lots of similar places like mine in the county," he said, "and they're not getting the same treatment."