Lobbyist Ann Eppard pleaded guilty yesterday to a misdemeanor for accepting $15,000 in illegal compensation when she was chief of staff for Rep. Bud Shuster (R-Pa.), who is responsible for billions of federal dollars as head of the House Transportation and Infrastructure Committee.

Vernon A. Clark, 69, a lobbyist for clients affected by Boston's "Big Dig," the Central Artery/Third Harbor Tunnel Project, also pleaded guilty to a misdemeanor for making the payments to Eppard in 1989 and 1991 and giving her an interest-free $30,000 loan in 1993.

"Eppard, while a key congressional staffer, took money and other benefits from a lobbyist with clients who sought government action in connection with the Big Dig," said U.S. Attorney Donald K. Stern. "The machinery of government is corrupted by under-the-table payments designed to smooth the way for lobbyists."

U.S. District Judge Joseph L. Tauro sentenced Eppard and Clark each to a fine of $5,000, and fined Clark another $5,000 for a tax offense. As part of a plea agreement, the government dismissed an earlier indictment that charged Eppard with extensive violations of the federal gratuities statute in accepting $230,000 in illegal payments and loans from Clark and others from 1988 to 1993.

"I am greatly relieved that this long and painful ordeal has reached a positive conclusion," Eppard said in a statement released by her lobbying firm Ann Eppard Associates of Alexandria.

"At no time did Ann Eppard intend to violate any rule of law," said Richard M. Egbert, Eppard's attorney.

The government said in court filings that Eppard "did knowingly receive and accept compensation" from Clark, who used an unnamed relative of Eppard "as a conduit" for the payments and loan. Eppard received the compensation from Clark for services involving his clients, and she acted on their behalf by "meeting with agency representatives and third parties in connection with" the tunnel project.

Sources knowledgeable about the case said the broader indictment against Eppard was undermined by the Supreme Court's April 27 ruling in U.S. v. Sun-Diamond Growers of California. Sun-Diamond, a fig, raisin and hazelnut cooperative, had been accused by independent counsel Donald C. Smaltz of giving illegal gifts to former agriculture secretary Mike Espy. Sun-Diamond's 1996 conviction was overturned in 1998 by the D.C. Court of Appeals, whose decision was affirmed by the Supreme Court.

The Supreme Court found there had to be a direct link between a gratuity and a specific official act for the federal gratuities statute to apply. Otherwise, the court found, the law would criminalize such harmless activities as high school sports teams giving jerseys to the president, because he has education issues before him as part of his duties.

Under the plea agreement, Eppard and Clark are not cooperating witnesses, a source said. "There never was anything pending against Shuster," said a federal official. "This is effectively the end of the case."

Shuster praised his former aide, saying, "The fact that all the charges against her were dropped . . . in exchange for a misdemeanor speaks for itself. Our trust and respect for Ann remains intact."

Congressional Accountability Project director Gary Ruskin, who has filed an ethics complaint against Shuster based on the lawmaker's dealings with Eppard, said he was dismayed that the Sun-Diamond ruling undermined the prosecution.

"Our public corruption laws have taken a very big hit," Ruskin said. "How did such a seemingly strong case result in such a weak plea bargain? This is a slap on the wrist."

Staff writer Juliette Eilperin contributed to this report.

CAPTION: Ann Eppard, former aide to House transportation committee chairman Bud Shuster (R-Pa.), at federal court in Boston, pleaded guilty to misdemeanor.