Federal agencies shipped more than 8,300 tons of toxic wastes over a six-month period to a California hazardous-waste landfill that the Enviromental Protection Agency had found in "significant violation" of environmental laws, according to the General Accounting Office.

The GAO said that EPA officials banned waste shipments from Superfund cleanup sites to the Kettleman Hills landfill, about 60 miles south of Fresno in the San Joaquin Valley, in October 1984. The agency took the action after inspectors found the facility had no system to check for ground water contamination and was violating numerous other waste-disposal rules.

Despite the EPA ban, other federal agencies continued to ship wastes to the site, including materials tainted with polychlorinated biphenyls (PCBs) and contaminated soil removed from toxic-waste dumps on federal property. More than three-quarters of the federal waste came from Defense Department facilities, including the Riverbank Army Ammunition Plant, McClellan Air Force Base and the Mare Island and Long Beach naval shipyards in California.

The report was released yesterday by Rep. John D. Dingell (D-Mich.), who called the situation "an outrage."

"Even though the EPA banned further dumping of Superfund hazardous waste, other federal agencies not only continued to dump, but increased the amounts they dumped," Dingell said.

According to the GAO, the Defense Department awarded a new contract to the facility more than six months after EPA imposed its ban even though a precontract evaluation noted that Kettleman Hills was having trouble complying with the law.

While the EPA may block federal grants and contracts under the Clean Water and Clean Air acts, it has no similar authority under hazardous-waste law or Superfund. "The only way EPA can prevent federal agencies from using a particular disposal facility is to close the facility," the GAO said.

The Kettleman Hills facility remained open for business while state and EPA officials negotiated with its operator, Chemical Waste Management Inc. of Oakbrook, Ill., to bring it into compliance with the law.

The GAO said federal agencies it questioned have policies requiring the use of licensed hazardous-waste sites, but few went further to determine if the sites met license requirements.

Dingell said the situation raises liability questions for the federal government.

The GAO agreed, noting that EPA's policy of banning Superfund waste from questionable disposal sites stemmed from fears that the new sites "may themselves become uncontrolled hazardous waste sites requiring cleanup under Superfund sometime in the future."