James W. Sanderson, who represents the only U.S. company capable of burning hazardous wastes at sea and was EPA Administrator Anne M. Gorsuch's choice for the agency's No. 3 job, talked to Gorsuch last month and helped persuade the agency to speed approval for proposed ocean burnings.

Sanderson, who the Justice Department is investigating on unrelated conflict-of-interest charges, was acting on behalf of his client, Chemical Waste Management Inc., a subsidiary of the nation's largest waste-disposal company.

It was the third time the Environmental Protection Agency went out of its way to accommodate Chemical Waste Management, the owners of the incinerator ship Vulcanus I.

Last year, under a quickly processed research permit, the company was allowed to burn millions of gallons of PCB-laden oils in two test runs of the Vulcanus. When the scientific data from the first test proved inadequate, the EPA agreed to pay for a more complete analysis.

Sanderson was seeking a permanent operating permit for the Vulcanus, which could give the company a lucrative edge on the incinerating market. After Sanderson's discussion with Gorsuch, a top EPA official overruled a staff decision to reject the permit. While it has not been formally issued, it could now be cleared within a matter of weeks or months.

Internal EPA documents show, however, that agency scientists had serious questions about the reliability of data obtained from an initial test burn aboard the Vulcanus. Don Oberacker, an EPA scientist who monitored the first test burn, warned in a memo last June that the analysis had "failed to result in any defensible . . . data for PCBs." Oberacker wrote the memo to "document my legitimate concerns" that more PCBs would be burned "before sufficient and credible scientific data on the performance efficiency of the facility have been provided."

The memo was not widely distributed at the EPA because, Oberacker explained in a cover note, it would be "embarrassing to Anne Gorsuch ." The EPA was preparing to issue stiff new regulations for land-based incinerators and officials were afraid it would appear that "we are giving loose permits out one door while insisting on stringent performance on the other."

Burning toxic wastes such as PCBs at sea, if it can be done safely, is considered a potentially crucial step toward solving the nation's hazardous waste problem. EPA officials say they are seeking solid data on what kinds of toxics can be burned at sea and how completely they can be destroyed.

According to agency sources, the EPA took steps to improve the data on a second test burn by hiring an independent contractor. But the agency had to pay for the analysis itself, at a reported cost of about $300,000, because the research permit did not call for the company to pay it.

"Chemical Waste Management wrote the permit," said one agency official. "There was no research protocol."

Chemical Waste Management was paid between $10 million and $25 million for two test burns of toxic waste that EPA allowed aboard the Vulcanus last year.

Sanderson, a friend of Gorsuch's, worked as a paid, part-time adviser to Gorsuch from March, 1981, through June, 1982, while also representing Chemical Waste Management, Chevron Shale Oil, Western Crude Oil and other legal clients.

He withdrew from consideration for the No. 3 job in the agency because of an investigation into charges that he improperly influenced an agency decision affecting the Denver Water Board, one of his clients.

Gorsuch acknowledged through a spokesman that she discussed the stalled permit for the ship with Sanderson when he was in Washington last month.

"They did talk about the ship Vulcanus," said EPA spokesman Clay Jones. But he said Gorsuch could not remember whether she directed Frederic Eidsness, EPA's assistant administrator for water, to order his staff to prepare the permit.

Sanderson acknowledged yesterday that he has been handling the Vulcanus issue for Chemical Waste Management, but he would not confirm reports that he pressed Gorsuch and Eidsness on the matter. "I don't comment about who I talk to or who I don't talk to on any client matter," Sanderson said. He said he "thought it was unlawful" for EPA to hold up the Vulcanus permit.

Steven Schatzow, director of EPA's Office of Water Regulations, said that last month he rejected a request from a Chemical Waste Management vice president for speedy consideration of the ocean burning permit. But when he returned from vacation Jan. 31, Schatzow said, he found that Eidsness had overruled him.

"It is certainly not unusual for people who don't get the answer they want from me to take it over my head," Schatzow said. He said he is not often reversed by his superiors.

Eidsness was in London and could not be reached for comment.

Chemical Waste Management applied about a year ago for three EPA permits to burn hazardous waste on Vulcanus I and a newly built sister ship, Vulcanus II. Schatzow said he decided the three permits should be considered together because they involve similar issues. But Chemical Waste Management concluded that the complex process was hindering approval of the burning of the least toxic substance, organohalogens, on Vulcanus I, and has won EPA's separate consideration for that permit.

The incinerating ship also is an issue in EPA's controversial settlement last October with 24 companies at a hazardous waste dump in Seymour, Ind. The companies signed a $7.7 million cleanup contract with Chemical Waste Management, and the agreement says that some of this waste will be burned aboard the Vulcanus, even though the company still lacks the necessary EPA permit to do so.