The prize is the right to develop the Portal site, a scruffy, 10-acre tract at the foot of the 14th Street Bridge, a place where Conrail trains rumble into the District, government workers jam their cars into parking lots and the General Services Administration literally shakes coal.

But three teams of developers overlooked the site's tawdriness yesterday and told the District's urban renewal agency that if they could win the development rights, there would be nothing but classy hotels, vistas of the Capitol along a rebuilt Maryland Avenue, elaborate office buildings, plazas for noontime strolls and new life on the Southwest waterfront.

All three development teams came equipped with elaborate dog-and-pony shows worthy of the potential gold mine they are fighting over, the last major urban renewal site in Southwest Washington.

In a daylong series of presentations, the developers treated the five-member board of the Redevelopment Land Agency to multimedia slide and video shows with Hollywood-like voice-overs and orchestral accompaniments extolling the fine points of their designs, their experience and financial capabilities and their concern for the city and its residents.

The prize is such that all three development teams include some of the city's and the nation's biggest real estate companies, prestigious architectural firms and numerous locally prominent black lawyers and entrepreneurs.

One team, Portal Associates, includes Washington developer Conrad Cafritz; big-time Boston developer Mortimer B. Zuckerman, who recently bought U.S. News & World Report; and Roger R. Blunt Sr., who heads one of the largest black-owned construction companies in the nation and is the upcoming president of the Metropolitan Washington Board of Trade.

A second team, Portals Development Associates, is headed by Western Development Corp., the Georgetown developer that built the chic Georgetown Park shopping mall and is finishing the controversial Washington Harbour project on the Potomac River in Georgetown. Western has a variety of minority partners, including arts advocate Marie Barksdale, consultants John Clyburn and Roy Littlejohn, restaurateur Manuel V. Fernandez, real estate broker Carlton Jones and attorneys Carolyn Jordan and David Wilmot.

The third group, Rock-Portal Inc., includes Rodman C. Rockefeller, a son of the late Nelson A. Rockefeller; Marathon U.S. Realties Inc., a subsidiary of the giant Canadian Pacific rail line, and local firms Farr-Jewett Portal Partners and First City Associates. The group hired James W. Rouse, the developer who shepherded the new town of Columbia into existence and devised the popular Harborplace eating and shopping malls on the Baltimore waterfront.

In addition to including local minority partners on their teams, the developers all pledged to contribute $100,000 or more annually to a variety of Southwest Washington community, tenant and cultural groups to meet a renewal agency requirement that the developments give some benefit to Southwest and Washington residents.

The grand promises, however, were not new for the agency, which more than three years ago awarded development rights of the Portal site to Banneker Associates, a group that included shopping center magnate Theodore N. Lerner and developer Melvin Lenkin. But by October 1983, the agency rescinded its approval of Banneker when the agency and developer could not agree on a price for the site. The developers originally offered $45 million for the site but later offered only $38 million.

The redevelopment agency reopened the bidding on the site this year but limited the contest to the five groups that bid previously. Banneker dropped out and so did a group headed by parking magnate Dominic Antonelli, leaving the three revamped teams that made their presentations yesterday.

The agency has not set a price for the tract this time while awaiting a final appraisal of its worth. Agency board chairman James E. Clay said the city is prepared to sell or lease the land, depending on negotiations with the developer it selects.

Clay set no date for picking a winner, but he added, "We will do it expeditiously."

Aware that the redevelopment agency had been burned after selecting a developer, all three groups tried to show in their presentations that they would not leave the agency hanging a second time.

David Childs, head of the Washington office of the Skidmore, Owings and Merrill architectural firm, which designed Portal Associates' entry, described its proposal for nine traditional federal-looking buildings as "simple and quiet. I understand the need for pragmatism and reality." Portal Associates' plan, costing $250 million, calls for construction of a 370-room Holiday Inn but has little space for retail stores.

Childs' design would leave open a portion of the Conrail tracks that cross diagonally through the Portal site, which is bounded by 12th, 14th and D streets and Maine Avenue SW.

By contrast, the other designs call for construction of a deck over most of the railroad tracks and more space for retail stores.

All three proposals include massive office buildings. The $460 million Portals Development plan, drafted by architect Arthur Cotton Moore, includes arches, curving structures, turrets, a host of flags, pools of water on the plaza over the railroad, a 600-room Radisson Hotel and a walkway over the Southwest Freeway to a small park along the Southwest waterfront.

The $368 million Rock-Portal proposal, designed by the New York architectural firm of Brennan Beer Gorman, would include a 300-room Marriott Hotel and a large Rouse-designed walkway with shops over the freeway leading to still more stores along the shoreline.