Through a new review process adopted last year, the Environmental Protection Agency has managed to cut in half the time it takes to approve changes the states want to make in the way they administer the Clean Air Act.

Kathleen M. Bennett, assistant administrator of EPA for air, noise and radiation, said that while the agency is pleased with the results so far it wants Congress to let it stop reviewing a large number of the state changes.

Under the Clean Air Act each state is required to draw up a plan showing how it plans to meet federal air standards. The plans are known as state implementation plans (SIPs). Whenever a state wants to make any change, major or minor, temporary or permanent, it must be approved by the EPA.

John Calcagni, the EPA staffer responsible for much of the new program, estimated that no more than 20 percent of the actions have "any substantial impact on air quality."

Daniel Goodwin, head of Illinois air pollution control and a frequent critic of the lengthy SIP process, agreed that many minor SIP reviews should be eliminated, and said, "A lot of progress has been made in the last nine months."

But Goodwin said the EPA "has been too reluctant to disapprove SIP revisions that should be disapproved. Most states have some things that come through the state system that really are shaky, and that probably should not receive federal blessings."

Goodwin also said that the Reagan administration has failed to correct deficiencies in state SIPs, something the EPA is authorized to do. "That's unfortunate, because a credible threat of federal action is strong incentive for a state to do the right thing," he said.

EPA decided to revamp its SIP process last July after "after industry and state complaints reached a loud roar," Calcagni said. At that time 643 state requests were sitting in EPA regional offices. It took the EPA an average of 425 days to repond to one.

The EPA completed about 20 cases a month, so just eliminating the backlog would require 32 months. In addition, about 30 new requests were submitted to the agency each month. "So every two months, we'd fall another month behind," Calcagni said.

Under the new system EPA expects to eliminate 90 percent of the backlog by the end of this month. And more than 100 of the 230 new cases submitted since August already have been completed. The agency has reduced the time it takes to review minor changes to 123 days and to between 280 and 300 days for major actions. The vast majority of SIP revision requests have been approved, Calcagni said.

Under the old system an EPA regional office reviewed a state's submission, drew up a proposal and sent it on to headquarters. Headquarters reviewed the proposal, then published it in the Federal Register. The EPA regional office then had to study any comments that were filed, and write a final notice, which headquarters reviewed before it was published in final form.

To streamline the system, EPA split the SIPs into major changes and minor changes, the latter being those it thinks will not provoke any comments. The agency now publishes the minor changes in the Federal Register as final actions. However, the agency delays the change for 60 days and, if comments are received, the EPA will go through the full rule-making process.

More than 200 cases, or about 40 percent of those the EPA has reviewed since last July, were handled this way. Comments were received on only four of them.

David Hawkins, who held Bennett's job during the Carter administration and is now an attorney with the Natural Resources Defense Council, praised the agency's efforts to reform the review process. But he added, "Just because a SIP receives no public comments doesn't mean it is necessarily non-controversial."

On major revisions the EPA now skips the final headquarters review if no public comments are received, as was the case with 40 to 50 of the revisions of the past year.

In about 20 other cases, EPA used a system known as parallel processing, in which the agency and the state go through their review process simultaneously. This can cut the time to about five months.

"This requires the state to come to us early on," said Tom Helms, chief of EPA's air control office. "And it's not the savior. Controversial things are hard" to do this way.

The regional offices are now expected to complete a proposal within five months and its final reviews in another five months. Headquarters staff will have up to two months to complete each of its two reviews. Any revision that is behind schedule is brought to Bennett's attention.

Calcagni said the review is going more quickly now, simply because each staffer is held accountable.

"We've taken a lot of flak as an agency about staff cuts gutting the environment," he said. "Here's an example of where, by using basic management techniques, we're able to solve a major problem without throwing bodies at it."