While the powers that be are busy turning the big wheels of government, Jean Croft is busy greasing the smaller ones.

Croft is a congressional liaison for the Environmental Protection Agency, which means working to keep Congress and EPA on good terms. And that, Croft will tell you, is often a difficult task.

"The thing that makes being a liaison at EPA so interesting," the longtime Republican says, "is that no matter what decision the agency makes, it is bound to make someone angry . . . . That's what makes this job a real challenge."

Croft's day begins, typically, by answering 15 to 30 telephone calls from congressional staff members who want information from EPA--and want it immediately.

For example, on a recent morning, the office of Sen. Strom Thurmond (R-S.C.) wanted to know if a South Carolina cotton farmer could get an emergency use permit for a pesticide that is restricted by EPA. Then aides to several Arizona congressmen called to find out whether EPA had decided to use emergency federal funds to clean up a trailer park that was built on top of an old asbestos dump in that state.

"I try to have all the answers back to the congressional staffs by the end of the day, but sometimes that's impossible," said Croft. "A lot of times, I don't know the answer, but I know who to call and that saves them from making 17 different phone calls to the agency."

Croft also works with the more than 40 committees and subcommittees that have jurisdiction over some part of EPA. On the same day that Croft threaded Thurmond's pesticide question through the agency, she also helped prepare a briefing paper for a subcommittee interested in new regulations that EPA had recently proposed for polychlorinated biphenyls (PCBs).

That same week, Croft briefed two EPA officials on what kind of questions they probably would be asked when they testified before another subcommittee investigating toxic wastes. She also made final arrangements for a field hearing in Tulsa, Okla., where another subcommittee planned to grill regional EPA officials about Tar Creek, a badly polluted area of Kansas and Oklahoma.

"I think we have to answer to more committees than any other federal agency," Croft said. Since October, EPA officials have testified at 65 congressional hearings on such varied topics as acid rain, formaldehyde and diesel engine emissions.

The Office of Congressional Liaison played a role in each. The office, which has a fiscal 1982 budget of $1.3 million, includes 15 employes who work on the liaison staff and 17 who write testimony for EPA officials and draft legislation.

Lee Modesitt, who recently took over as director, said, "The key to being a successful congressional liaison rests on two things: giving members of Congress the respect that they need, want, and deserve . . . and giving them the information that they also want . . . . The two must go together."

Liaison officers--and federal agencies--are barred from trying to lobby Congress by using federal funds for campaign contributions, financing letter-writing campaigns or taking out advertisements. It is not illegal, however, for them to "inform" Congress about legislation.

Several times each week, Croft eats lunch at the Capitol with friends, who also generally are key staff members on congressional committees. They chat about politics and gossip and then Croft usually plugs pending legislation affecting EPA. If Croft gets stuck with the bill, she said she pays it out of her own pocket.

Modesitt and Croft have both worked the Hill before as congressional aides. Modesitt spent nine years on the staffs of Rep. Ken Kramer and Sen. William L. Armstrong, both Colorado Republicans.

Croft got her first political job in 1956 when she went to work for a Republican House member from California. Since then, she has worked on several presidential campaigns, including all of Richard Nixon's. When Nixon was elected to his first presidential term, Croft won a job as a congressional liaison staff member for the Interstate Commerce Commission, where she stayed until Jimmy Carter was elected.

Croft was working at the American Trucking Association when Ronald Reagan took over. She received a call from a Republican friend who asked if she wanted a job at EPA, and joined the agency as a GS15.

A common complaint among congressional staffers is that liaison staffs often don't know much about the agency they represent, a charge that Croft said has merit. "It takes you a year to really get going," she said, "but it is important that liaisons be members of the administration team so that they can push and defend administration policies."

Croft said she treats Democrats the same as Republicans. "I'm going to sound like Pollyanna," she added, "but the one thing that you learn rather quickly is to tell a congressional office the truth even if you know that it might be used against you."

The reason, Croft explains, is "credibility." The liaison staff spends 99 percent of its time working with congressional staff members, she said. "It's a very professional relationship and your reputation is important . . . . Our only tool is information . . . . The facts can be very persuasive, but you have to be accurate or no one will trust you the next time around."

When it comes to hard-nosed arm-twisting, Croft said, most congressional liaison staffers step aside. "If that goes on, it goes on at a higher level than mine"--usually by the White House, the Office of Management and Budget or a federal agency's administrator.

When she joined EPA, Croft was in charge of dealing with members from California, New England and the Midwest. But the office recently was reorganized by subject so that Croft now answers questions about research and development and water programs.

"The best thing about this job is that there is no sameness to it," Croft said. She paused, then added, "That was sameness, not saneness."