Questions have been raised about the recent sworn testimony of former Environmental Protection Agency official Rita M. Lavelle before Congress, including possible discrepancies in her account under oath of when she learned that her former employer was involved in an EPA hazardous waste case.

Lavelle, the former director of EPA's hazardous waste office, told a House Public Works subcommittee Thursday she did not know that Aerojet-General Corp., her former employer, had disposed of wastes at a California hazardous waste dump until last June 17, the day before she recused (disqualified) herself from the case.

But one EPA official, who asked not to be identified, said that Lavelle was explicitly warned about Aerojet-General's role in the case in a meeting on May 28, 1982, about three weeks earlier than Lavelle had said in testimony. According to this source, who participated in the May 28 meeting and recorded it on a calendar, at least seven EPA officials were present at the session in Lavelle's conference room.

James Bierbower, Lavelle's attorney, said yesterday he would not respond to any account from an anonymous source. "As a matter of policy, I don't bother with, look into or comment upon hearsay," he said. "Get me someone who is willing to put his neck on the block and then we'll deal with it."

The May 28 meeting had been called to brief Lavelle on what EPA was doing about the Stringfellow Acid Pits, a large toxic waste dump near Riverside, Calif., this participant said. Lavelle was given a packet of briefing materials on the site, which then was being considered for a cleanup grant from the agency's $1.6 billion "Superfund."

Soon after the meeting began, the source recalled, Edward A. Kurent, then EPA's associate enforcement counsel for waste, asked Lavelle to look in the briefing packet at a list of the companies that were known to have disposed of wastes at Stringfellow. These companies were to be notified of their legal liability by EPA and faced possible prosecution if they did not agree to contribute to cleanup of the site.

Kurent reportedly pointed out that Aerojet-General Corp. was among the firms on the list. He said it would be prudent for Lavelle to recuse herself from any further involvement in the case because Lavelle had been a communications official for Aerojet, the source said.

"She was told flatly and out loud at that point," this participant said.

Lavelle expressed surprise, but said that she did not intend to make any decisions about the Stringfellow case at that meeting, the source said. The meeting reportedly continued for another hour with discussions of possible strategies for resolving the Stringfellow case.

In the following weeks, according to two EPA sources, lawyers in the office of EPA general counsel Robert M. Perry questioned Lavelle several times about her role in the Stringfellow matter. On June 18, she agreed to sign a recusal statement that they say was drafted in Perry's office.

Lavelle gave a different account when she testified before the Public Works subcommittee on investigations and oversight. She said that "the first time" she realized Aerojet had disposed of wastes at String- fellow was at a staff meeting on June 17. "I left the meeting and my staff passed out a letter of recusal" which she signed the next day, Lavelle said.

Rep. Elliott H. Levitas (D-Ga.), chairman of the Public Works subcommittee, said he also has heard questions about the accuracy of Lavelle's account and is conducting a routine review of her testimony. He said he planned to call one of the participants in the May 28 meeting before his subcommittee this week.

"My information is there was an earlier meeting on Stringfellow ," Levitas said. "We just can't let the matter sit there. I think we will have to ask those questions."

Lavelle testified that she was present at some meetings after June 18 where Stringfellow was briefly mentioned or described in a "status report." But she added: "I in no way involved myself in any policy- making or decision-making after that date, consistent with the recusal."

The Stringfellow site has become controversial because an anticipated Superfund grant was held up during last year's campaign. Some EPA officials say the delay was meant to prevent then-governor Edmund G. (Jerry) Brown Jr., the Democratic candidate for the U.S. Senate from California, from taking credit for the cleanup.