U.S. EPA Administrator Christie Todd Whitman gave the go-ahead yesterday to a Clinton-era plan requiring General Electric to spend half a billion dollars to dredge PCB pollution from 40 miles of the Hudson River. Her draft order, which has been sent to New York state for a 30-day review, came after weeks of speculation that the Bush administration might cave to pressure from G.E. and scale back the dredging to a six-mile pilot project. The company has spent millions of dollars trying to convince the EPA and the public that the river is naturally cleaning itself and that dredging now would only make the pollution problem worse. Enviros said last-minute lobbying by Republican Gov. George Pataki (N.Y.) helped to convince Whitman to stick with the Clinton plan.