The voluminous record book officially closes today on Case No. 84-9C, otherwise known as Techworld -- the huge and hugely controversial set of buildings proposed for a two-block site next to the Convention Center in downtown Washington. Members of the city's independent Zoning Commission must now make their decision, which they are scheduled to do on March 11.

Despite the complexity of the project and thousands of pages containing millions of words of contradictory and often accusatory testimony, the Techworld case is fundamentally simple: The proposal should be flat-out rejected unless the developer agrees to change it in key respects.

In reality, the pressures on the zoning commissioners to approve the buildings, including the full weight of the city government from Mayor Barry down through the ranks, are intense. By concentrating on short-term economic benefits and refusing to heed the most enlightened voices among those who helped to forge its own comprehensive plan, the city has played into the hands of the developer, Giuseppe Cecchi, president of International Developers Inc., who has said time and again that he will drop the $240 million, 1.57-million-square-foot project unless he gets his way.

Unfortunately, one of the elements Cecchi says is necessary to the project -- connecting 13-story buildings on both sides of Eighth Street NW with a heavy six-story bridge structure -- is so contrary to the unique, open spirit of the capital city, and particularly to this very special north-south street, that it should not even be considered. Another important aspect of the design -- sizably narrowing the Eighth Street right-of-way -- is inadvisable at best. There is also the matter of sheer bulk: The Techworld design is an ingenious model of how to squeeze every square inch out of the city's building regulations.

Poor Eighth Street. Time has not treated it kindly along the three-block stretch between G and K streets NW, between the National Museum of American Art and the old D.C. Central Library. There are a few more or less distinguished, if poorly maintained, remnants of the street's former life as a low-rise quarter of houses, churches and neighborhood stores, but much of the land, reflecting the high-density commercial uses assigned it, has been cleared for action. The Techworld project, to include a large hotel and structures to house exhibitions, services and offices for high-tech industries, would be situated on the almost totally empty northernmost blocks, bordered by Seventh, Ninth, I and K streets.

And yet, even in its forlorn condition, this segment of Eighth Street represents a great opportunity. People on both sides of the Techworld debate agree about that. The street, after all, is potentially one of the more beautiful north-south connections in the city, mainly because, with his amazing foresight, Pierre Charles L'Enfant designated it as such.

True, a grand Greek Revival building, originally the Patent Office and now the National Museum of American Art, occupies the lot he chose for a national church, and a pretty Beaux Arts structure, formerly the central library and now part of the University of the District of Columbia, is situated on the prominent square upon which he proposed placing monuments to the American Revolution and its heroes. These are but changes in detail, however. In spirit, these fine public buildings are in accord with L'Enfant's vision of squares "most advantageously and reciprocally seen from each other . . ."

This is one reason to find the Techworld proposal lacking. With that cumbersome bridge structure over a narrowed street, it treats an important part of the city's basic plan -- the plan without which Washington would not be the great city that it is -- with grave disrespect.

Another reason is that the proposal violates the design, historic preservation and downtown elements of the city's comprehensive plan, each of which pledges in some way to reinforce the principles of spaciousness and openness that make Washington unique.

A third is that to condone this proposal would be to send a message that the city government does not take seriously one of the most laudable, if difficult, of its stated goals for downtown renewal: to make it a "living downtown" by encouraging people actually to live there.

A fourth is the project's excessive height and bulk. The opinion of the lawyer for the National Capital Planning Commission -- who has said the 130-foot height of the structure was allowed in error and would put the city's height limitation law in "serious jeopardy" -- should not be taken lightly.

In fairness I should say that a revised design by principal architect Wayne Williams is an improvement over an earlier design in several respects: a promising change in materials, from allover reflective glass to alternating facades of concrete and glass; a general straightening out of building lines, as they relate to the streets; and the addition of "Chinese garden" elements to the landscaping plans, appropriate for a project on the edge of Chinatown.

Still, none of these details in any way mitigates an overpowering proposal that poses such fundamental threats to the basic design principles of the city.