In what would be a major policy reversal at the Environmental Protection Agency, Administrator-designate William D. Ruckelshaus told a Senate committee yesterday that he would move "expeditiously" to clean up hazardous waste dumps before negotiating with waste generators on who will pay the cost.

The "Superfund" cleanup law was designed to provide money for speedy action on dumps that threaten public health. But under former administrator Anne M. Burford the agency had adopted a policy of identifying generators and negotiating cleanup contracts before tackling the task.

Ruckelshaus, testifying before the Senate Environment and Public Works Committee in the third day of hearings on his nomination to succeed Burford, said he thought criticism of the policy was well-founded.

"There was too much emphasis on who pays as opposed to cleaning up the dump," he said. He also indicated that Superfund may be one area slated for budget increases. "I think it is likely that there will be more money spent," he said.

Ruckelshaus also promised to address "with some degree of urgency" the question of acid rain, caused when sulfur dioxide emissions combine with atmospheric moisture.

Ruckelshaus was responding to concerns expressed by members of the Senate committee, which last year overwhelmingly approved amendments to the Clean Air Act that would impose new curbs on sulfur dioxide emissions from coal-burning power plants and other industries.

But he said he already had made that commitment to Secretary of State George P. Shultz. Acid rain is becoming an increasingly prickly foreign policy problem because of damage done to lakes and streams in Canada.

Acid rain and dump cleanups joined a list of EPA priority issues that got even longer yesterday, as senators probed Ruckelshaus' attitudes on everything from state responsibilities to the U.S. role in international environmental efforts.

Chairman Robert T. Stafford (R-Vt.) requested and got a commitment that Ruckelshaus would review all of the agency's classified documents to see which should be made public. Sen. Lloyd Bentsen (D-Tex.) extracted a promise that no permits for hazardous waste incineration at sea would be approved without public hearings in his state.

Under questioning about his record as a business executive, Ruckelshaus put up a spirited defense of his employer, the Weyerhaeuser Co., and took a poke at the environmental groups that testified Tuesday on his own environmental record and his company's.

"Those were the groups I attempted to meet with from time to time" as EPA administrator in the early 1970s, he said. "I felt these were intelligent, dedicated people--almost never factually inaccurate." But the testimony, including Environmental Action's characterization of Weyerhaeuser as one of the nation's five worst polluters, was a "theater of the absurd," he said.

"If I was so bad, why was I asked by many of these groups to join their board of directors?" he asked. ". . . I'm not as sure some of the facts I'll be getting are as good as I've gotten before."

Admonished later by Sen. George J. Mitchell (D-Maine), however, Ruckelshaus said he still intends to meet with environmental groups "even if they are as antagonistic as they were two days ago."

And, returning to the general good humor that has characterized his confirmation hearings, Ruckelshaus noted that an official of the National Wildlife Federation endorsed his nomination. "I appreciate that," he said. "I commend him--not necessarily for his judgment, but for his courage."