The U.S. District Court has temporarily dismissed a suit against the National Park Service that sought to block a giant interchange and bridge on the George Washington Memorial Parkway south of National Airport.

The interchange is planned as the major entrance to the proposed $300 million Potomac Center high-rise development, a project predicted to be as large and twice as high as nearby Crystal, City.

The suit, brought by local residents who seek a full environmental review of the impact a bridge and interchange would have on the scenic parkway, was dismissed by Judge Oliver Gasch as premature, "not yet ripe for review" by the courts, because the Park Service is not presently considering any specific plans for the bridge and interchange.

However, Judge Gasch said in his opinion that a comprehensive environmental impact statement "may well be justified as soon as the Park Service approves any plan for construction of the access structure."

He added that because of the "widespread interest in his proposal" he would "implore (the Park Service) in the strongest possible terms" to immediately begin reviewing the proejct and to involve the public in the decision-making process.

Until two weeks ago the Park Service was considering plans for the interchange, but rejected them as "unacceptable . . . and hazardous" and requested the developer, Charles Fairchild, to come back with a new interchange proposal.

Fairchild's plans had called for up to four lanes of parallel service roads, within 10 feet of the parkway, a four-lane bridge and seven separate entrances and exits into the high-rise project.

The citizen suit contended that such a large interchange would detract from the historic parkway and that the number of cars the complex would provide parking for - up to 18,800 according to figures given the Park Service by the developer - would overwhelm it with traffic. The parkway already is jammed during rush hours with the maximum traffic federal highway officials consider the road can handle.

New plans for a bridge and interchange already are being prepared and the developer told the court during the hearing last week that he hopes to award a construction contract for the bridge by Dec. 1.

The suit does not contest the landswap agreement made in 1970 between the Park Service and Fairchild, under which he traded 29 acres of marshland the Park Service wished to preserve at Dyke Marsh, along the parkway south of Alexandria, in exchange for access to the parkway opposite Daingerfield Island south of the airport.

A maximum of about 1.3 acres of land would be needed for the bridge entrance that the Park Service and Fairchild envisioned in 1970. However, the bridge, roads and ramps recently proposed by Fairchild, and rejected by the Park Service, would require more than 5.5 acres of parkland.

The parkway access is valuable because it opens up for development more than 40 acres of otherwise largely inaccessible land owned by the Richmond, Fredericksburg and Potomac Railroad.

The attorney for the citizens, David Prensky, told the court last week "they regret it (the swap) was made" but are challenging only the current plans to build a bridge and interchange on parkway by Daingerfield Island and the Washington Sailing Marina.

The suit does contend, however, that the Park Service made the trade without holding public hearings, without putting the required notice in the Federal Register and without filing an environmental impact statement as required under the then six-month-old National Environmental Policy Act, The Park Service contends it did all that legally was required at the time.

The five area residents suing the Park Service are sailors who use the marina. They have incorporated as a nonprofit group called the Daingerfield Island Protective Society (DIPS).

While DIPS may not be challenging the 1970 land swap specifically, the group could kill or significantly reduce the size of the Potomac Center project if it succeeds in blocking or limiting the size of the bridge and interchange.

A major objection raised by DIPS is that the Potomac Center proposed in 1970, and for which the Park Service agreed to permit a parkway entrance, is vastly different from what is now proposed.

The historic parkway to Mount Vernon now would be the major entrance to Potomac Center, Prensky told the court, although when the Park Service approved the land swap the parkway was to be only a secondary entrance.

In 1970 the Park Service had said the major entrance was to be the Northeast Expressway, Prensky said, an interstate route considered questionable even then and since killed by Virginia highway officials.

Before approving the land swap in 1978 the Park Service had concluded Potomac Center would have a "minimal" traffic impact on the parkway because of the expressway, a small entrance to it on nearby Slaters Lane (a two-lane road that feeds onto the parkway several hundred yards south of the proposed bridge interchange) and a Metro subway station proposed for the site which many Potomac Center commuters would use.

The Northeast Expressway is dead and even the Metro station now is in doubt, Prensky told the court. Metro and Alexandria have contended all along that the developer must build the station, which could cost up to $20 million, but Fairchild is now insisting the city and Metro should construct it.

Not only have the alternatives to auto access from the parkway dwindled since 1970, but the number of cars projected to use the Potomac Center has more than quadrupled.

In 1970, in a brief study of the environmental impact of Potomac Center and the land swap - not the detailed study required under NEPA - the Park Service estimated that only about 4,000 cars would park at Potomac Center, with only a portion of them using the parkway. That compares with parking for an estimated 18,800 cars presently proposed, with the vast majority of them using the parkway.

Fairchild said in an interview last month that the exact sixe of Potomac Center and the amount of parking has not been determined. However, in an affidavit filed with the District Court two weeks ago, Fairchild said he plans to spend more than $6 million on a computer-run, multilevel underground parking system.

There is no mention of Metro in the affidavit, which reviewed the history of Potomac Center. It only mentions a monorail that Fairchild proposed be built between National Airport, Potomac Center and Alexandria's downtown historic district. Fairchild did not offer to build it and city and airport officials have dismissed the idea as unrealistic.