The Westinghouse Electric Corp. reached an agreement yesterday with the government to clean up six toxic dumps in the Bloomington, Ind., area at a cost that may reach $100 million.

Under the settlement, Westinghouse will be required to build a hazardous-waste incinerator capable of destroying more than 650,000 cubic yards of soil contaminated with polychlorinated biphenyls (PCBs) that the company dumped in pits and lagoons near its Bloomington plant for more than a decade.

The Environmental Protection Agency called the agreement "the largest hazardous-waste settlement in the history of the agency." Justice Department officials said it is likely to be the most costly cleanup ever undertaken in a federal toxic-waste case.

By federal estimates, the cleanup will take 17 to 20 years and cost $75 million to $100 million. But Westinghouse officials, seeking to cushion the impact of the announcement on the corporation's stock prices, said the government's cost estimates are excessive.

"There will be no impact on earnings," said company spokesman Bill MacLaurin, who said Westingthouse expects to offset "a substantial amount" of the cleanup costs by burning municipal waste in the incinerator and selling the excess steam and electricity to neighboring industries.

"There will be a revenue stream," said Westinghouse official Paul Jones. "We expect that to offset a goodly bit of it."

Included in the agreement are four sites in Monroe and Owen counties that were deemed dangerous enough to be included on the EPA's priority list for Superfund cleanup. From the late 1950s through the early 1970s, Westinghouse dumped thousands of gallons of PCB-contaminated wastes and other manufacturing byproducts at those sites and two others in Monroe County.

According to the EPA, soils in the area are contaminated with up to 380,000 parts per million of PCBs, and toxic materials have migrated into ground-water supplies and nearby streams. PCBs, once commonly used as an insulating material in electrical equipment, have been linked to cancer in laboratory animals.

EPA officials said the wastes pose no immediate health threat. The company will be required to control the migration of toxic materials while its incinerator is under construction and awaiting federal operating permits.

"We've tested all the wells around the sites, and they all came up clean," said Barbara Magel, an EPA attorney in Chicago. "Under the decree, Westinghouse will have to clean up the surface and put in control measures."

EPA Administrator Lee M. Thomas hailed the agreement and said that it "provides for the ultimate destruction of the PCB wastes, rather than for long-term landfilling."

But the settlement drew criticism, as well, including a sharp response from EPA official Hugh B. Kaufman, a hazardous-waste authority and frequent in-house critic.

"It seems to me that Westinghouse is being rewarded for breaking the law," Kaufman said. "This agreement puts them into the incinerating business and gives them a wedge to get a permit. At the worst, they're out the cost of excavation; at the best, they'll make millions."

EPA attorney Magel said Westinghouse will be allowed to burn PCB wastes from other sites in the Bloomington area as long as it is burning its own wastes, but she said the incinerator will not be allowed to burn toxic materials after the Westinghouse cleanup is completed.

"The community and the surrounding area did not want a commercial operation going on," she said. "We didn't feel the need to insist, so there will be no trucking waste from other areas."

When the cleanup is finished, according to Jones and Magel, Westinghouse will either sell or lease the incinerator to the city as a municipal-waste burner or will dismantle it.