A plan for a huge, multimillion-dollar International Cultural and Trade Center, to be located in southwest Washington near the waterfront, is speeding along lickety-split. This is happening in part because of an amazing display of coordination between agencies of the local and federal governments and in part--and this is both amazing and gratifying--because it is a good plan.

Many big ifs remain concerning the ultimate form the development might take, and nearby businesses and residents are understandably concerned about its effect upon their interests. But in key respects the center could be the means to make a stalled dream come true.

The location is crucial. The complex is slated to occupy 17 acres of publicly owned land south of the Southwest Freeway, between 7th and 10th streets SW. The financial advantage of this location is obvious--it would be difficult and tremendously expensive to assemble so much land elsewhere in the city--and its practical benefits are equally important.

Properly designed and managed, the center could transform the southwest waterfront into a vital hub of commerce and recreation. This was the sadly thwarted vision of the original southwest urban renewal plan.

The functions seem to fit, too. The center has not been planned simply as a means to fill some handy vacant property with transplanted federal office workers. Nearly half of the 1.6 million square feet would be used for commercial and cultural exhibitions described by one supporter as a "permanent mini-world's fair," along with auditoriums and retail outlets thematically organized as an "international bazaar." Additional space will be provided for parking 1,800 cars.

That still leaves a sizable chunk of space left over for offices and other functions but the probable users have been carefully selected to relate to the general theme of the place. Foreign governments, for instance, will be offered the opportunity to rent space for "satellite chancery offices," and the State and Commerce departments will locate certain bureaus in the complex--an export trade institute, government offices that deal with international trade, and a centralized passport and visa office, among others.

"There's very little space in the project that isn't 'public' in some way or other," says an architect for Mariani & Associates, part of a consulting team (also including Anderson Notter Finegold Inc. of Boston and Washington, and Bryant and Bryant of the District) hired to examine design alternatives for the project.

The idea for an international trade center on the site originally was part of a study of the entire Washington waterfront, published last February by the Federal City Council, a nonprofit civic organization. Since then the idea has received enthusiastic backing from federal agencies, foreign governments and the District government, which sees the project not only as a source of jobs and tourist income but also as a way to get a handle on the nettlesome home-rule issue of controlling the siting of foreign missions in the city.

(For detailed background on the International Cultural and Trade Center plan see today's Real Estate section.)

Despite the bandwagon psychology that seems to be coalescing around the plan, there are a few major obstacles on its way to becoming a reality. The biggest legal hurdle is to change the southwest urban renewal plan--no simple matter following U.S. District Court Judge Harold H. Greene's decision some years back requiring the consent of any nearby landowner or lessee upon whom the change would have "an adverse indirect effect of substantial dimension."

Given the probability that even a small number of disgruntled nearby residents could block the project under this rule, the center's advocates expect that the matter will end up in Congress, where they will propose not only a change in the urban renewal plan but also the creation of an unusual, quasi-public body (modeled on the Pennsylvania Avenue Development Corp.) to finance, develop and administer the project.

If all goes according to a schedule established by the Federal City Council, construction of the mammoth $215 million enterprise could begin in 1985, and it could be operating by 1987--an optimistic schedule. Even so, now is the time to begin taking a careful look at the design of the proposed new entity. It contains some very thoughtful, creative aspects and some sizable potential problems.

Site plans and a large model prepared by the consultants demonstrate unequivocally what a huge building this will be, spread over most of the 17-acre site and stretching more than four city blocks, east to west, from 7th Street to the 11th Street bridge. Obvious care has been taken to preserve views and break up the mass of the structure: two terraced office towers (each about 110 feet high) step back from the waterfront and the main public plaza, and the main theater (one of three) is located so it will read as a separate structure.

Furthermore, the public plaza has been intelligently situated--it will take the place of the underused Banneker Overlook at the western termination of 10th Street--a long noble axis in the Washington tradition, starting at the Mall and ending . . . nowhere. Correcting this deficiency is by far the most promising aspect of the physical design.

As the consultants see it, the plaza will have its own dramatic punctuation mark--a steel and glass hemisphere, 90 feet high, that also will serve as the main public entrance to the exhibition and retail areas--and it will lead to a low, air-rights building bridging Maine Avenue. This could become the long-awaited missing link between the Mall and the southwest waterfront, enhanced by an electrically operated trolley running at five-minute intervals along 10th Street between Constitution Avenue and the new center.

Still, while looking at materials provided by the consultants one cannot help but wonder about the final form of the place. One can worry about the big things, and also about the smaller things, about the concepts and the details.

The big worries are fairly obvious. As currently proposed, with the notable exception of the hemisphere, the building masses have that standard ribbon-window look. One doesn't have to advocate a Disneyland in southwest Washington, where boring new architecture found a home, to want something with more image, more surprise, more color than seems to be contemplated here.

And then there is the very size of the building: it will take a tremendous application of ingenuity, more than is so far evident in this design, to connect the parts of this building in a way that seems less than Brobdingnagian. Some reduction in size would help, too. Is this really the necessary place for the State Department training center? Maybe so, maybe not, but now is the time to ask these questions.

Smaller worries abound, though none at this stage is insurmountable. These concern pedestrian connections between the building and the residential area to the west and the planned Portal office-hotel complex just a block to the east; the spatial relationships between the plaza and the buildings; the urban hardness of the plaza itself; the tricky configuration of retail and exhibition areas; the ample opportunities for unlikable blank walls . . . and many more.

But if this huge new project needs careful scrutiny, it also deserves support, for the center represents an opportunity to invigorate the southwest waterfront and, at last, to truly cross the great superhighway moat that separates the southwest from the rest of the city.