It was 1970, and William D. Ruckelshaus had just been named head of the newborn Environmental Protection Agency. Word traveled fast that the boss was an avid rose gardener, and an eager employe presented him with some black-market bug killer sure to kill anything that crawled.

As Ruckelshaus has told the story, he ran the man out of his office, warning: "Get that stuff out of here! This is a brand new agency. You'll ruin its credibility and mine from the start."

Such stories abound about Ruckelshaus' tenure as the EPA's first administrator, from 1970 to 1973, when the nation's environmental laws were in their infancy and he was at the center of an emerging battle between industry and environmental groups over anti-pollution regulations.

A careful and respected lawyer, Ruckelshaus was known for calling in stenographers when he met with industry lobbyists because, as he said recently, "The administrator is a sitting duck. You have to protect yourself."

It was that reputation for integrity and independence that led President Reagan to ask Ruckelshaus to return to the top job at the EPA at its most troubled time since its founding. Congressional critics of the agency were quick to predict an easy Senate confirmation of Ruckelshaus, 50, because of that reputation.

"He has the character and reputation and integrity to restore the EPA to something like the credibility it had before the last two years," said Sen. Robert T. Stafford (R-Vt.), chairman of the Senate Environment and Public Works Committee, which will handle the Ruckelshaus nomination.

But Stafford and other congressional leaders said the appointment of Ruckelshaus alone is not enough to resolve their concerns about the agency, now the target of six subcommittee investigations into charges of conflicts of interest, political favoritism and mismanagement. Anne M. Burford, Reagan's first EPA administrator, resigned earlier this month as the investigations intensified.

For starters, they said, the agency will need a housecleaning of many political appointees, and major budget increases to make up for what they estimated is a 50 percent cut in the EPA's spending power since Reagan took office.

Ruckelshaus will come under close scrutiny, Stafford said, for his activities in the 10 years since he left the federal government. As a Washington lawyer, he represented industries regulated by the EPA, including the manufacturers of vinyl chloride and aluminum.

Since 1975 he has been senior vice president of Weyerhaeuser Co. of Tacoma, Wash., one of the world's largest forest products concerns, which is regulated by the EPA's air, water and toxic pollution control programs.

While there, Ruckelshaus has been a vocal critic of certain provisions of the Clean Air Act, which he said in 1981 Senate testimony had caused the country to "spend more than is wise" to control air pollution, and resulted in "overkill, underkill and political backlash."

Still, environmentalists praised him yesterday in almost one voice, while remaining critical of the administration's environmental record. "Our fear is that Mr. Ruckelshaus is merely a refreshing sprout in a clear-cut forest," Jay D. Hair, executive vice president of the National Wildlife Federation said.

Rep. James J. Florio (D-N.J.), chairman of a subcommittee investigating the EPA, said he respected Ruckelshaus' "integrity and independence," but that evidence continues to show the White House's approach to EPA has been "the very opposite of independence."

"If the president of the United States asks you to assist on a matter that's important to the country, you have an obligation to take that request seriously," Ruckelshaus said in a news conference with Reagan.

Ruckelshaus' reputation for independence was forged less at the EPA than in the Justice Department during the Watergate scandal. He served briefly as acting FBI director, and then as deputy attorney general, a post he resigned on Oct. 20, 1973, rather than fire Watergate Special Prosecutor Archibald Cox as Cox sought access to President Nixon's Oval Office tape recordings.

His independence from the Reagan administration has been clear for two years. He is board chairman of the Urban Institute and a trustee of the Conservation Foundation, which have criticized Reagan's urban and environmental policies. His wife, Jill, a leading women's rights advocate on the U.S. Civil Rights Commission, was not reappointed to the panel by President Reagan.

At the EPA from 1970 to 1973, Ruckelshaus pulled together a range of regulatory offices that had until then been scattered through the federal bureaucracy: water programs in the Interior Department, air in Health, Education and Welfare, pesticides in the Agriculture Department and other agencies. He was instrumental in setting the air and water quality standards that are the heart of the Clean Air and Clean Water acts.