President Reagan's attempt to make a "fresh start" at the Environmental Protection Agency last week marked a sharp departure from the two years in which the White House had largely neglected the agency and put its programs on the back burner of presidential priorities, according to senior administration officials.

Preoccupied with the larger difficulties of Reagan's troubled economic program, presidential aides said they had devoted little attention to the agency from the outset of the administration.

Nor, they said, did they have an inkling of what was to follow when the name of Rita M. Lavelle came up at a routine White House personnel meeting Feb. 2 and it was decided that Reagan should fire her as the EPA's toxic waste chief.

That dismissal unleashed allegations of conflict of interest, mismanagement and political manipulation in the EPA's $1.6 billion hazardous waste cleanup effort. But it also underscored the detachment and even indifference with which Reagan and senior presidential assistants had regarded the environmental agency.

Abruptly, this detachment ended last week. Working under White House chief of staff James A. Baker III, top presidential aides have launched their own effort to rebuild the agency's management, beginning with temporary appointment of a phalanx of highly regarded bureaucrats to serve as deputies to EPA Administrator Anne M. Burford. Although Reagan decided to keep Burford, his appointments made it clear who will be running the agency.

The significance of this move is that the political wing of the White House has taken charge of a large political problem for Reagan. Although they recognized it belatedly, some White House officials now believe that protecting the environment is an important issue among middle-class voters who are a valuable Reagan constituency.

Thus, even though they had neglected the EPA from the first days of the administration and waited several months before filling the agency's top job, White House officials immediately saw the political damage the controversy could cause. To blunt it, Baker and his aides reached out to other agencies for help. Other measures are certain to follow, including a study of the toxic waste cleanup program.

Not all of the details of White House contacts with the EPA are known. But in interviews last week, several key administration officials, who asked not to be identified, said that the White House was unaware of the depth of problems at the agency, despite clues that a crisis was brewing.

"Most of these agencies like the EPA are running on autopilot," one senior administration official said. "There is no way the White House can know everything that's going on."

But it is also true that Reagan's detached management style made the EPA a blind spot for the White House.

Since the days of his California campaigns and governorship, Reagan has angered organized conservation groups by expressing strong views on environmental issues. These include his famous remark, "A tree is a tree--how many more do you need to look at?"

This was repeated in the 1980 presidential campaign, when steelworkers in Steubenville, Ohio, confronted Reagan with complaints about EPA regulations on burning high-sulfur coal. Reagan responded with a rambling, off-the-cuff monologue.

Among other things, he suggested that the Mount St. Helens volcano was a bigger polluter than automobiles, that trees cause air pollution and that oil slicks off Santa Barbara, Calif., once purified the sea breezes.

Later, as his campaign plane flew over a smoldering forest fire, Reagan aide and future presidential press secretary James S. Brady said loudly to reporters, "Killer Trees!"--a line that became permanently affixed in the lore of the campaign and as a symbol to Reagan's environmental critics.

For all of his rhetoric, however, Reagan has never personally made the environment a front-burner issue in office. Rather, he has delegated it to others, who have shaped the details of his record for him. For example, in California, he appointed a conservation-minded lumberman, Norman Livermore, to run state natural resource programs, and Livermore assembled a moderate record on environmental issues.

Once he entered the Oval Office, Reagan again delegated away environment questions. But instead of Livermore, the top natural resources job went to development-oriented James G. Watt, who, as interior secretary, impressed White House officials with his ability and willingness to push ahead on his own while the president's men focused on the more important economic issues.

It was common knowledge in the early days of the administration that Watt had taken Burford under his tutelage. As chief of the White House Cabinet council on natural resources and the environment, Watt talked about forcing policy changes on a reluctant bureaucracy. The result, according to one informed administration official, was that Burford spent considerable time learning Watt's techniques.

"She . . . showed no loyalty for her employes," one informed administration official said. "Anne was just not a good manager," the official added, and "operated secretively." This was combined with "people who weren't very sophisticated" in dealing with industries that had interests in EPA decisions, the official said.

While the White House had set up the Cabinet council system partly to keep tabs on major policy decisions, much of the EPA's work was through regulations that did not always come through the Cabinet councils, one senior White House official said. As a result, he added, the White House was sometimes in the dark about EPA activities. For most of this time, the EPA was under the policy-making apparatus run by White House counselor Edwin Meese III.

It is also clear that the White House was never totally detached from the EPA. Last March, presidential assistant Craig L. Fuller met with Burford--known as Anne M. Gorsuch before her marriage last weekend--to try to get a grasp on what the agency was doing, and her office later provided White House officials with "issue alerts" on potentially controversial points.

Also last year, White House officials decided to use the powers of an incumbent president to best advantage in the fall campaign. They gathered information about forthcoming federal grants from all departments and agencies so announcements could be timed to help Republican congressional candidates.

The result was that many such announcements were used for political purposes last fall, and the EPA "Superfund" program to clean up hazardous waste apparently was not excluded.

Some White House officials said they also failed to see the potential for management problems in the $1.6 billion program, created by Congress at the end of the Carter administration. "There is a lot of discretion in how you use the money--and you don't find many of those kinds of funds in government," one official said.

As a remedy, the White House is now considering appointing David F. Linowes, a professor at the University of Illinois with experience in government and business, to study the Superfund law for possible improvements, officials said.

In addition, some White House officials said they failed to anticipate that Reagan's claim of executive privilege over disputed EPA documents would look different when questions came to light about possible political manipulation and conflict-of-interest in the program.

What officials originally thought was a sound legal position upholding executive privilege unexpectedly became clouded by allegations that followed Lavelle's firing, they said.

Within days of the firing, Baker moved to take control of the EPA controversy within the White House. "It was no longer an EPA problem--it was the president's problem," one official said.

To help Reagan out of a fix, Baker turned to the bureaucracy Reagan had often criticized. He found some of the government's most respected managers, such as Assistant Labor Secretary Alfred M. Zuck and Assistant Transportation Secretary Lee Verstandig.

Still, White House officials said in interviews that they do not expect a quick end to the EPA controversy. "There may be people who have a silver-bullet theory that they can kill this one in a single shot," one official said. "But I don't think it will work."