Officially it is all quiet on the Georgetown waterfront.But under the cover of that quiet, the contestants are retrenching, regrouping an negotiating. We may soon see yet another redevelopment plan for this industrial slum - a Georgetown waterfront plan that everyone can agree on.

Not since Verdun in the first world war has there been a piece of real estate more fiercely embattled. There were lawsuits, character assassinations, broken friendships and reputations, and millions of dollars wasted on studies an restudies. Georgetown residents hated the urban renewers, federal planners fought municipal planners, conservationists hated developers and everybody abhored the Whitehurst freeway that puts the entire waterfront under its ugly shadow.

Now suddenly the freeway is forgiven and accepted as inevitable as highway deaths and taxes.

The common ground on which the waterfront warriors are meeting is a proposed greensward along the Potomac from Rock Creek to key Bridge.

This waterfront park has become possible - as distinct from probable - because of two recent developments:

One is that it has recently been determined that the large portion of waterfront land that belongs to the District of Columbia may be used as a park. The District bought this land largely with federal highway trust fund money to build its portion of a new I-66 super freeway on it. The freeway, and the Three Sisters freeway bridge it was to lead up to, are now dead. But federal highway administrators have told the District that it may keep the land as long as it is used for some transportation purpose - such as bicycle paths, hiking trails and parking.

The other news is that the Inland Steel Development Corporation, which owns a large chunk of water-front south of K Street from 31st Street almost to 30th Street, has given up. Inland was going to build a marina, waterside cafes, shops, offices and apartment houses on this site. It was to make the waterfront urban.But during all these years of warfare and court action, it could do nothing with this land but pay taxes on it. The property is now for sale.

The bombshell that blasted the waterfront warriors out of their entrenched positions, however, was a bill Sen. Charles McC. Mathias (R-Md.) unexpectedly introduced in the Senate. The bill would give the Interior Department title to all the land between the C. & O. Canal and the river and between Rock Creek and a line 400 feet west of Key bridge in payment of the fair market value prevailing March 1. In other words, the Georgetown waterfront would be made a national park like Cape Cod or the Grand Canyon.

The senator's phone rang a lot after that. His response was to invite the callers in - the government agencies, the developers and the citizen militants.

"There we found ourselves all in the same room, looking at the maps and various proposals and - for the first time in the long waterfront war - actually talking to each other," recalled Ben Gilbert, the head of the Municipal Planning Office. The mayor was there with his man Gilbert. So were David Childs, chairman of the National Capital Planning Commission; Carter Brown, chairman of the Fine Arts Commission, representatives of the federal and municipal highway departments and of the National Park Service.

Mathias called it "a love-in."

The "mini-city," with its mix of housing, offices, hotels and stores in buildings up to 90 feet high which the city had proposed and zoned for, melted away in the warmth of the sudden togetherness."

The new intergovernmental consensus would, first of all, exclude the area between the Canal and K Street (under the Whitehurst Freeway) from the Mathias bill. Most of that area is built up and there seems no reason why the federal government should buy a piece of the city it could not and need not change. The only exceptions are the historic Forrest-Marbury and Francis Scott Key houses along M Street at 34th and 35th Street, which the Park Service would like to restore and landscape to serve as an entrance to the new Potomac Park area.

The "love-in" consensus also includes enlarged marinas and boat houses east and west of Key Bridge and a lively entrance to the park at the bottom of Wisconsin Avenue. A charmingly drawn proposal by Stephen Kloss of National Captial Planning Commission calls for a "bazaar" at Wisconsin Avenue and K Street where street vendors would find shelter. There might also be a restaurant boat and a wooden floating platform for boats to land and people to linger and enjoy the water.

On the east, the park would be linked across Rock Creek with the riverside park in front of the Kennedy Center. It would turn the unused, truncated freeway stumps over Rock Creek into pedestrian walkways with potted trees and flowers, overlooks and benches. The monsters were built a dozen years ago to spearhead an "inner loop" freeway the highway people hoped to ram through the Cosmos Club on Massachusetts Avenue and burrow under the Lincoln Memorial on the Mall.

There is also general agreement among the government agencies that there ought to be some development on the so-called Chessie site bounded by K Street and Rock Creek Park on both sides of what 30th Street, would be, if there were a street there.

The city's municipal planning office favors a proposal of the Western Development Corporation that would build four-story townhouses, and a commercial building of moderate height over two levels of parking garages. The Fine Arts Commission, along with the citizen representatives, favors no development at all. The National Capital Planning Commission is studying various alternatives, but sees the virtues of some building here.

A building complex would not only yield some tax revenue - an estimated $1 million a year - to the city, but also bring people and life to the area and help hide the god-awful Whitehurst monster. There needs to be some transition between the park and the high buildings north of K Street. Unless there are buildings that lead up to them, they look like a Chinese Wall.

Another unresolved problem is parking. The ideal would be a sunken parking garage with a mini-bus shuttle system through Georgetown that makes it possible to ban all, or most parking on the congested Georgetown streets. This is difficult to accomplish because the proposed park is below the flood plain. Flood protection costs a lot.

But if the new "lov-in" spirit Mathias, has kindledal so spreads to the Georgetown militant, these questions can be worked out.

Another thing that must be worked out is the appearance of the Whitehurst Freeway. First of all the antique must be made safe. Beyond that, local architecture students might be invited to propose ideas for things like decorative railings and column supports, interesting lighting, super-graphics, and gewgaws or something under the elevated freeway that makes K Street more attractive. It should be fun and it should draw some of the roaming suburban youngsters away from crowded M Street and Wisconsin Avenue.

The big question is whether Congress will be willing to spend anywhere from $16 to $20 million to buy a riverside park for rich Georgetown, which is remote from the majority of the city's residents. But then, George-towners are a vocal group.