General Electric Co plans to put aside another $500 million to dredge toxic chemicals it dumped into New York's Hudson River more than 30 years ago, bringing the clean-up bill to $1.33 billion over two decades.

The largest U.S. conglomerate said on Thursday it expected one-time gains, including a favorable tax settlement, to offset the after-tax charge, which it will record in the fourth quarter. It did not change its overall performance forecast.

The U.S. Environmental Protection Agency last week ordered Fairfield, Connecticut-based GE to dredge deeper into the river to remove sediment that included polychlorinated biphenyls -- or PCBs -- which have been shown to cause cancer.

GE dumped the chemicals, which it had used as an insulator in electric components, into a 40-mile stretch of the river north of the state capital Albany, some 150 miles north of New York City, for three decades prior to discontinuing their use in 1977.

It has already spent about $830 million since 1990 on prior cleanup efforts.

Chief Executive Jeff Immelt told investors on December 14 that GE was working on a plan that would take the dredging of the Hudson off the table for future years.

PCBs are human carcinogens and can also affect the immune, reproductive, nervous and endocrine systems. One of the project's main goals is to achieve significant reduction in PCB levels in fish tissue.

Analysts, on average, expect the world's largest maker of jet engines and electric turbines to report a 14 percent rise in fourth-quarter profit to $3.45 billion, or 32 cents per share, according to Thomson Reuters I/B/E/S.

The company confirmed that it now expects its sale of a majority stake in NBC Universal to No. 1 U.S. cable operator Comcast Corp to close in January 2011, rather than this month.

GE shares were up 6 cents at $18.12 on the New York Stock Exchange.

(Reporting by Scott Malone, editing by Maureen Bavdek, Dave Zimmerman)

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