Charles Hamel, an influential oil industry whistleblower, and his wife, Kathleen, in 2006. (Pam Rutter/POGO.org)

Charles Hamel, an influential oil industry whistleblower whose efforts so exasperated his targets that petroleum companies hired private detectives for a spying campaign to ferret out his sources and methods, died April 9 in Marysville, Wash. He was 84.

His wife, Kathleen Hamel, confirmed the death but said she did not know the cause. The Hamels moved to Marysville about four years ago from Alexandria, Va.

Mr. Hamel’s work as a leading oil industry critic helped propel congressional investigations that uncovered safety and maintenance problems on the Trans-Alaska Pipeline System.

His transformation into an environmentalist was unexpected. As a former executive assistant to Sen. Mike Gravel, an Alaska Democrat, Mr. Hamel had been a booster for that state’s oil industry.

In the 1970s, he became an independent oil and shipping broker. He would buy oil in Alaska and move it on vessels that could pass through the Panama Canal, but he found that his clients were receiving oil “significantly diluted with water,” he later told congressional investigators.

His business collapsed by the early 1980s, and he initiated a lawsuit against the Alyeska Pipeline Service Co., a consortium of seven major oil companies that operates the 800-mile Trans-Alaska pipeline, claiming they had known of the watered-down oil.

When Alyeska refused to compensate him, he began to look into the consortium’s business and environmental practices. He interviewed Alyeska employees who were unhappy with the company’s conduct but who feared retribution by management. They provided Mr. Hamel with insights into unsavory practices, many involving air and water pollution at sea and on land.

“The more I heard, the angrier I got about what was going on,” he said in his 1991 testimony before the U.S. House Committee on Interior and Insular Affairs. “Alyeska was polluting the water by introducing toxic sludge, including cancer-causing benzene, into the pristine waters of Port Valdez and Prince William Sound. Alyeska was poisoning the Valdez fjord’s air by venting extremely hazardous hydrocarbon vapors directly into the atmosphere. There was no regulatory oversight, and thus no regulatory violations.”

He added: “It was as if the environmental regulations of the United States did not even apply north of the Canadian border — no regulators, no oversight, no enforcement — nothing. In fact, the oil industry wasn’t putting out anything but poison and lies.”

He lined up a platoon of internal whistleblowers and took his complaints to the Environmental Protection Agency and other oversight bodies in Washington and Alaska. He also contacted the news media and members of Congress.

He said the initial reaction was one of “profound skepticism everywhere that the oil industry would knowingly pollute the environment and harm their own employees in Alaska.”

A shift in attitude by the media and congressional investigators began after the 1989 oil spill by the tanker Exxon Valdez, which ran aground in Prince William Sound and cost billions of dollars in environmental damage.

Starting in 1990, Alyeska hired the Wackenhut security company to investigate Mr. Hamel after he received secret company documents from Alyeska employees. Mr. Hamel handed over the papers to Congress and reporters, and the revelations led the oil consortium to pay millions of dollars to repair pipeline corrosion and make other environmental upgrades. An Alyeska executive wanted to find out which company insiders were leaking information to Mr. Hamel.

Mr. Hamel’s conversations at home were recorded, his trash was searched, women were recruited to try to get him to divulge his sources and a dummy environmental organization was created to induce him to share information.

A lawsuit and a countersuit were filed. A federal judge in Washington who presided over the cases expressed his displeasure with the investigation into Mr. Hamel.

“This is not Nazi Germany or Russia,” U.S. District Judge Stanley Sporkin said. “These people have certain rights.”

he added, referring to the Hamels.The cases were settled for an undisclosed amount in 1993.

Charles Hamel was born in Waterbury, Conn., on July 12, 1930, and grew up in Watertown, Conn.

After Army service in Europe during the Korean War, he studied foreign trade at Georgetown University’s foreign service school. He became a staffer for Democratic Sen. Ralph Yarborough and Senate Majority Leader Lyndon B. Johnson, both of Texas, and Thomas J. Dodd of Connecticut.

His first three marriages ended in divorce. Survivors include his wife of 37 years, Kathleen Morgan of Marysville; a son from his first marriage; two sons from his third marriage; two grandchildren; and five great-grandchildren.

For many years, Mr. Hamel was involved in several business ventures and sat on the board of the Project on Government Oversight, a nonprofit government watchdog group.

Richard Steiner, a conservation biologist, oil industry watchdog and former professor, said Mr. Hamel paved the way for greater citizen oversight of the oil industry in Alaska and added, “The nation owes him a sincere debt of gratitude.”