Traci Watson, USA Today

WASHINGTON -- The Bush administration announced Thursday that it would make it easier for power plants, refineries and other industrial facilities to expand without having to meet strict air pollution rules.

The rules that would be relaxed are based on amendments made in 1977 to the Clean Air Act. They require older facilities that expand or modernize to install new pollution-control equipment. Such technology can cost hundreds of millions of dollars.

The new rules would have a major effect on old coal-burning power plants. Pollution from these plants has been linked to an increase in deaths from heart and lung disease. It can also cause acid rain, which damages trees and wildlife by leaching nutrients from soil and lakes. Under the new rules, utilities may be able to renovate these plants without having to install pollution-control equipment.

The change, according to the Environmental Protection Agency ( news - web sites), would allow companies to make their facilities cleaner and more energy-efficient and would not dirty the air. ''This administration is committed to clean air and will work vigorously to achieve clean air,'' President Bush ( news - web sites) said Thursday.

''These reforms are about making the Clean Air Act work effectively,'' EPA Administrator Christie Whitman said.

Critics, including environmentalists, Democratic and Republican members of Congress and some state officials, said the plan would demolish a key clause of the Clean Air Act. Several groups and state attorneys general said they would sue when the rules are finalized, possibly by the end of the year. The plan ''eviscerates the program,'' said Vickie Patton of Environmental Defense. ''It'll be hard to imagine a plant will ever again be subject to scrutiny.''

Environmentalists and industry groups focused on the EPA's announcement that it would revise its definition of ''routine maintenance.'' The current rules exempt companies from cleaning up if they're making routine changes to their plants. But all parties agree the formula for determining whether an activity is routine needs to be clarified.

The EPA said Thursday that it would issue a new definition of routine maintenance based on the cost of rebuilding the facility. A renovation project that costs less than a certain percentage of the facility's replacement value would not require a cut in the amount of pollution the plant emits. The EPA is considering numbers, which would vary by industry, from 1.5% to 15%.

Environmentalists said companies would simply spread out rehabilitation projects so they never exceed the limit.

Industry representatives said the new definition is key to providing them with the flexibility they need to keep their plants in good repair.

The EPA's proposal ''was a step in the right direction,'' said Scott Segal, spokesman for the Electric Reliability Coordinating Council, an industry group.

A straightforward evaluation of the competing claims is nearly impossible. The EPA didn't analyze how its plan would affect air quality, and it says doing so in the near future would be speculative.

The lack of analysis itself drew some fire.

''It defies explanation how the administration can propose and adopt sweeping changes to this program without doing an analysis,'' John Walke of the Natural Resources Defense Council said.

Walke said the Clinton administration proposed similar but more limited rules in 1996. At that time, the EPA published an analysis that estimated its recommendations would exempt roughly half of the plants required to clean up under current rules, though many of those plants would have voluntarily cut emissions.