Federal environmental officials ordered General Electric Co. to pay to remove tons of poisonous PCBs from the bed of the upper Hudson River, one of the largest dredging operations ever.

The dredging is expected to cost at least $500 million and could go much higher. If GE refuses to agree to the cleanup, the EPA can start work on its own and charge the company up to triple the cost.

Environmentalists, sharply critical of the Bush administration's early decisions on issues such as global warming and acceptable arsenic levels, praised the Environmental Protection Agency on Tuesday for resisting a fierce lobbying campaign from GE to weaken the plan.

"It's great news for the environment," said Katherine Kennedy, of the Natural Resources Defense Council.

The decision EPA sent to New York State on Tuesday effectively sets in motion the plan to remove 2.65 million cubic yards of sediment — enough to fill about 40 football fields 30 feet deep — from a 40-mile stretch of the Hudson River north of Albany. State officials still have 15 business days to review the plan, which doesn't become official until it is formally signed.

"We are going forward with this important cleanup," EPA Administrator Christie Whitman said Tuesday.

GE, which adamantly opposes dredging, had no immediate comment Tuesday. Spokesman Mark Behan said company officials had not yet seen the plan and would not comment until they reviewed it.

The company dumped 1.3 million pounds of PCBs into the river from its plants in Fort Edward and Hudson Falls north of Albany, before the federal government banned the pollutants in 1977.

The EPA decision largely mirrors a plan released by the Clinton administration almost a year ago to the day. Whitman endorsed that plan last summer, but environmentalists worried that she might be influenced to change her mind by heavy GE lobbying.

New York Gov. George Pataki, a Republican who urged Whitman last week to push forward with the cleanup, said he had not yet read the decision, "but it sounds at first blush very, very positive."

The decision comes after decades of conflicting studies over what to do with polychlorinated biphenyls, or PCBs, buried in the river bottom. Used as insulation and a coolant, PCBs have been linked to cancer in laboratory animals. The EPA classifies the oily substance as a probable carcinogen and says PCBs pose risks to wildlife and to people who eat fish from the Hudson.

The Whitman plans contains some changes from the Clinton-era blueprint.

It includes "performance standards" for air quality and noise but not for PCBs in the river water. GE had wanted water standards, believing that once dredging begins PCBs will be stirred from the bottom and flow downstream.

Pataki, environmentalists and many Democrats had lobbied against performance standards, saying they could expose the plan to legal challenges that would cause further delays.

Such water standards will instead be developed in the three-year design stage, where engineering details of the plan will be determined, the EPA said.

New York Attorney General Eliot Spitzer, while generally supportive, worried that the plan was being split into stages. He urged Whitman to ensure the cleanup's first of two stages is not "merely a pilot project." Progress will be reviewed before the second stage begins.

Among the strongest opponents to dredging are upstate communities where the work would take place. Residents fear long lines of dump trucks and related activities will disrupt their lives and do not want contaminated mud in their landfills.

Rep. John Sweeney, R-N.Y., represents the region where the dredging will take place and has been one of the plan's most vocal critics.

"While I'm still not enthralled by their continued endorsement of a massive, full-scale dredging plan at the very least this takes a more measure approach that is somewhat mindful of the potential havoc this project poses to affected communities," Sweeney said.