The Council on Environmental Quality has proposed eliminating the concept of "worst-case analysis" in measuring the environmental impact of federal projects, calling the requirement an "unsatisfactory approach" to weighing the risks of such projects.

The proposal caps a two-year effort by the Reagan administration to limit the reach of the National Environmental Policy Act, under which federal agencies must prepare detailed analyses of the potential impacts of projects ranging from dam construction to weed control in national forests.

Instead, agencies would be required to evaluate only "reasonably foreseeable" impacts, according to a Federal Register notice scheduled to be published today. CEQ officials said that category could include remote but potentially catastrophic events, such as a nuclear power plant meltdown, but only if there is "credible scientific support to suggest that the impact could occur."

"This proposal returns environmental analysis to the 'rule of reason,' " said CEQ Chairman A. Alan Hill.

In 1983, the CEQ stirred an outcry among environmental and public-health groups when it proposed to let agencies consider a "threshhold of probability" before conducting a worst-case analysis. Critics contended that such a threshhold would rule out analyses of some events -- such as a loaded oil tanker breaking apart in Galveston Bay -- that are admittedly remote but could be catastrophic if they occurred.

The new proposal, which closely follows a draft written by Justice Department officials last year, apparently would permit analyses of such events. But it still is unlikely to entirely please environmental and public-health groups.

"I'm not happy with it, but I could have been a lot unhappier," said Nicholas Yost, a lawyer for Advocates for the Public Interest. "It says they have to have studies of reasonably foreseeable events, but it is possible to write something that meets that criteria in a very unilluminating kind of way."

According to Yost, worst-case analyses were "more usable, more understandable. It is a phrase that people have come to look for and understand. It has a meaning."