Former Environmental Protection Agency official Rita M. Lavelle was acquitted yesterday of contempt of Congress charges resulting from her failure to testify about her management of the EPA's $1.6 billion "Superfund" for cleaning up hazardous waste.

Lavelle had been fired by President Reagan, was held in contempt by a 413-to-0 vote of the House and was indicted by a federal grand jury. But in the end, a U.S. District Court jury of eight women and four men needed just an hour and 45 minutes of deliberation to find her not guilty.

Lavelle, 35, smiled broadly as the jury foreman announced the verdict. She told reporters afterward that she was not bitter and now has "some faith, the system does work."

She said she now "would like to get a job and go home," adding that she did not know if she would be asked to testify again before Congress.

Lavelle, fired by Reagan Feb. 7 in an EPA shakeup, was indicted in May after the House held her in contempt for failing to respond to a subpoena issued by the House Energy and Commerce subcommittee on oversight and investigations. The panel was investigating allegations of mismanagement of the cleanup fund.

Yesterday, Lavelle testified for more than an hour, basing her defense on claims that she was too ill to appear and could not afford to fly to Washington from her home in California.

Lavelle said she had gone to California shortly after the House subcommittee subpoenaed her Feb. 23 to appear March 21.

"I was extremely depressed," Lavelle testified. "I was falling apart. I felt I was emotionally and physically unable to attend."

Lavelle said she had a painful throat polyp that she feared was caused by cancer.

Assistant U.S. Attorney Timothy J. Reardon III said her activities, including a two-day trip to Las Vegas, showed that health was not the problem.

"Who do you think you are to defy a subpoena from elected members of the House of Representatives . . . ?" he asked.

"I know who I am and I don't defy," she replied.

Reardon also argued that Lavelle never told House officials she had financial or physical problems and that she was "defying the legal process" by not appearing.

"There have been blatant appeals to your emotions for sympathy" in the case, he told the jurors. Lavelle not only defied Congress, he said, but did so "with a certain amount of arrogance."

Stanley M. Brand, general counsel to the Clerk of the House, said the verdict was "a setback for the House to enforce its subpoenas. We are just going to have to arrest people and try them in the well of the House," he said.

Under the Constitution, anyone held in contempt for refusal to testify can be tried by Congress and jailed in the House, where there is a "holding room," Brand said.

That procedure has not been used for more than a half-century. A statute passed in 1857 delegated prosecution of persons cited for contempt to the judicial branch.

Rep. John D. Dingell (D-Mich.), chairman of the full committee and the subcommittee that initiated the contempt action, could not be reached for comment.

If convicted, Lavelle could have been sentenced to a year in prison and a $1,000 fine.

A federal grand jury investigating whether Lavelle and other EPA officials committed perjury during congressional testimony is expected to conclude its deliberations soon, possibly as early as next week, Justice Department officials said yesterday.