A plan to improve the environmental health of the ailing Chesapeake Bay, North America's largest estuary, was unveiled yesterday by the governors of Maryland, Virginia and Pennsylvania and the mayor of the District of Columbia.

But the plan provided little that was new; most of the proposals were published in a 1983 report by the Environmental Protection Agency based on a five-year study. That report led to the federal government commitment to join the states in an effort to restore the quality of the bay. Yesterday's announcement made no commitments for funding of any projects, one of the key issues in the bay cleanup.

State officials said federal participation in the ceremonies eased their apprehension that federal support of the bay programs might be weakened by new strains caused by the growing deficit.

"It's the first time the coordinated plans of the three states have been put between covers and embraced by EPA," said Lou Panos, Maryland Gov. Harry Hughes' press secretary.

"Renewal of the federal commitment is the strongest indication yet that the bay programs will not become a casualty of the New Federalism and the federal budget deficit," Panos said.

The plan repeated five goals first stated in the 1983 publications -- to reduce the amount of fertilizer and animal waste going into the bay and its tributaries from sewage systems and farm runoff that are using up oxygen needed to support aquatic life; to control sources of toxic pollution such as industrial discharges into the bay; to restore or protect wildlife and fishery habitats; to manage related environmental programs in the states with concern for their effects on the bay, and to improve cooperative efforts at managing the estuary.

EPA Administrator Lee M. Thomas said the plan contains no overall cost estimates. "As far as money is concerned, you're clearly talking about millions and millions and hundreds of millions over time," he said.

The plan, which Thomas said is likely to be altered, symbolizes the commitment to the long process of improving the bay. "It will come in slow increments as the pollution loads on the bay are reduced. Now is the time for patience and support for the bay and those working to protect her as the hard work begins," he said.

It was a day of political salesmanship and show, but little detailed discussion. After the press conference announcing the plans in the District, three helicopters whisked the governors, Hughes, Charles S. Robb of Virginia and Dick Thornburgh of Pennsylvania, from Washington to tour pollution control projects in the bay area.

D.C. Mayor Marion Barry excused himself from the three-state tour and later met Hughes at the final tour stop in Southeast Washington at the Blue Plains Wastewater Treatment Plant, the largest sewage plant that discharges effluent into the bay or its tributaries.

Despite the political backslapping and light-hearted tone of the day, there were reminders that the Chesapeake Bay is an ecosystem in serious decline.

In each of the three states and in the District, facilities that symbolize a major source of bay pollution were chosen for the official tours.

In Lancaster, Pa., the governors visited Albert and Mary Jane Brenneman's 140-acre dairy and crop farm where state money has been used to control animal waste runoff and soil erosion.

Although Pennsylvania does not border the bay, the 440-mile Susquehanna River accounts for about half of the freshwater supply entering the estuary. This year Pennsylvania, which joined the restoration effort last June, launched a $2 million voluntary program to slow farm runoff in the state.

Leaving Thornburgh in Lancaster, Robb and Hughes flew to Elk Neck State Park in Cecil County Md., where they helped fishermen and biologists haul in nets containing seven species of healthy young fish, including rockfish, bluefish and white perch, and learned about a Maryland program to replant aquatic vegetation.

Next they flew to the elegant old Tides Inn, a country club in Irvington, Va., where oystermen worked on Carters Creek, newly opened for oystering this year after pollution closed the beds down in 1970.