Representatives of the nation's major environmental groups joined yesterday with some of their longtime adversaries - the oil, coal, steel and utility industries - to discuss a new way to resolve their disputes: environmental mediation.

The conference, sponsored by the Atlantic Richfield Co., the Sierra Club and the Aspen Institute, marked the creation of a national group to promote third-party mediation, the traditional tool in labor-management relations, to resolve environmental fights.add one mediators.

The group, called Resolve, is funded with an initial grant of $200,000 from Atlantic Richfield. Its board of directors includes former environmental protection Agency chief Russell Train; J. Michael McCloskey, Sierra Club executive director; William D. Eberle, president of the U.S. Council of the International Chamber of Commerce, and Robert Georgine, president of the Building and Construction trades Department of the AFL-CIO.

Faced with thousands of acrimonious conflicts over highways, dams mines and other commercial projects, environmentalists, industrialists and governments have clogged the federal courts with lawsuits in the last decade. Many of these disputes could be resolved if the parties would sit down and talk to each other, conferees agreed.

In the last three years, a few communities have used mediators successfully and the practice has begun to gain wider acceptance.

"It's a promising new technique," said Charles E. Warren, chairman of the Council on Environmental Quality, adding that government agencies, corporations and citizens have all "suffered from prolonged litigation."

Warren cited two successful environmental mediation cases. In Montgomery County, he said, a shopping center was turned down in the 1960s after citizen opposition. Several years later, the developer hired a Washington mediator, Malcolm Rivkin, to negotiate with citizens. The result was the recently completed White Flint Shopping mall.

In exchange for citizen support, thae developer agreed to environmental restrictions such as citizen review of site design and lighting lower buildings, special landscaping, and a ban on gasoline stations and drive-in restaurants.

In another case, Gerald W. Cormick, a University of Washington professor, mediated a dispute over a proposed $100 million dam near Seattle. Farmers wanted the dam for flood control. Other citizens opposed it as growth producing and destructive of the beautiful recreational river.

After months of meetings, all parties agreed to a compromise that included building a smaller dam on a different site and establishing a basin-wide planning commission.

Susan Carpetner of the Rocky Mountain Center on the Environment said mediation has worked in several Colorado disputes, one over a sewage plant that would have encouraged growth in a small town, another over 11 coal mines that would have disrupted farming.

However, participants said many disputes won't lend themselves to mediation, for example, the nuclear breeder controversy. Opponents won't settle for a small reactor, or one on a different site, since they oppose the breeder on principle.