A Fairfax developer's longstanding plans to build a massive office, apartment and hotel project called Potomac Center between National Airport and Alexandria have been ended because he failed to start construction on time.

The project, planned by Charles M. Fairchild, was consistently opposed by civic associations, environmentalists and local politicians. One of their chief arguments was that cars coming from the Potomac Center would slow the already heavy rush-hour traffic on the George Washington Memorial Parkway.

Fairchild leased the 38-acre tract from the Richmond, Fredericksburg and Potomac Railroad in 1970, but lost his lease two weeks ago because he had failed to begin development within a specified period.

Richard Beadles, an RF&P vice president, said yesterday that while the railroad has no one "waiting in the wings" to develop the land, it is the railroad's "hope, desire and intent to see that piece of land developed."

Fairchild's plans for Potomac Center--called Crystal City II by its detractors, after a large development nearby in Arlington--called for a 1,300-room hotel, several hundred condominiums, 2.6 million square feet of office space and parking for about 11,000 cars.

The developer has argued that the project was blocked because the Interior Department reneged on an agreement to provide him the crucial access from the parkway, which is owned by the U.S. government. His attorneys have filed suit in U.S. District Court in Alexandria to try to recover a wilderness area in Fairfax County that he gave to the government as part of an agreement under which access was to be granted.

That 28-acre wilderness area along the Potomac shoreline, called Dyke Marsh, is now a bird sanctuary prized by environmentalists and bird watchers. Fairchild gave it to the Interior Department at the same time he purchased a 99-year lease on the Potomac Center project from the railroad. According to Fairchild's suit, the railroad was a party to the agreement with Interior.

In correspondence with Fairchild over the past year, the Interior Department has maintained that it was willing to grant access all along but was prevented from doing so because Fairchild never formally submitted site plans for his project to the government.

Fairchild countered that he couldn't produce site plans until he knew what kind of access he would be permitted.

Railroad lawyers said they believe the government's promise of access to the land from the parkway reverts to the railroad now that Fairchild's lease has been terminated. That is disputed by Fairchild. The Interior Department had no comment on the suit yesterday.

Late last summer, a Chicago development firm that expressed interest in buying the lease from Fairchild backed away from the Potomac Center project, saying that the "basic problem" with the site was that costs of providing access to it -- including construction of a bridge interchange over the parkway and an access road for trucks -- were too great.