ANY TIME a small part of Washington threatens to break out into lively activity, there always seem to be some officials ready to stop it. The latest example is the area just north of Pennsylvania Avenue, where 7th and 8th Streets NW run up from the National Archives to the National Portrait Gallery. That's where a neighborhood rich with housing, shops, art galleries and sidewalk cafes was ready to take shape, promising to balance out the heavy presence of the nearby FBI Building.

The officials in this case are those running the Pennsylvania Avenue Development Corporation. Pleading that it's too costly to let more than a token handful of people live and shop and stroll within their monumental precincts, these officials are now cutting back on housing and on urban amenities to make room for more big office buildings.

This area may well offer our last real chance to reconnect the Mall with the District's downtown, so as to help tourists find the theaters, shops and museums that are not on the Mall but scattered throughout the rest of the city. Such a reconnection could boost the local economy, and let tourists have a better time. That's one reason the 1974 Pennsylvania Avenue plans called for the avenue to be a "bridge, not a barrier ... by making it easier for people to cross from one side to the other and by giving them a reason to do so."

If the development corporation's officials really fear a lack of funds, and don't simply think that office buildings give tourists that "reason" to cross Pennsylvania Avenue, there is a way out. All along the north side of the avenue, whenever a new building goes up, a rule left over from long-dead plans still mandates that sidewalks be widened by 50 feet. That's why little pieces of empty monumentality start and stop, causing old buildings to jut out strangely, and wasting valuable land. Even assuming a conservative price of but $350 a square foot, the wasted land in front of the FBI Building alone is worth $7 million.

Last year, one of the corporation's officials estimated -- quite roughly -- that $15 million would pay for putting enough housing in the plans to create a basis for a real neighborhood, for making a small part of it available to people of middle and low incomes, for putting back enough shops and galleries to lead tourists all the way up 8th Street, for saving more valuable old buildings, and for not giving up and just building more offices. Changing the sidewalk policy for the rest of the avenue now would save about $20 million -- enough for all the improvements, even allowing for the roughness of the estimate.

A key area for a better sidewalk policy is at Market Square, across the avenue from the Archives, where the corporation's current plans call for knocking down several handsome old buildings just so new ones can be put up, anywhere from 25 to 100 feet further back. This would push back the city, making any "reason" tourists have for crossing the avenue that much harder to see, and that much harder to reach.

Current plans also call for a bandshell as a memorial to the Navy in Market Square. This is fine in itself, as the great history of the Navy deserves great recognition. Besides, bands and orchestras -- maybe even passing guitarists -- would certainly attract some tourists. The design for the memorial is an improvement over what was programmed earlier, but it has unfortunately come out as an arch needing one face of its opening filled with a temporary partition during performances to act as an acoustic reflector. As the partition is to be put in the Pennsylvania Avenue face of the arch, this means tourists on the other side would catch little of the sound of music, and would see nothing at all of the performers. Bandshells can come in all kinds of designs: This particular one has given a "reason" for crossing the avenue, but has then covered it up.

> Mark McInturff has helped sketch out how current plans might look if they were improved with better funding and with greater concern for tempting tourists into the city. Two round towers are shown marking 8th Street's entrance on Market Square, and reflecting the monumental symmetry of the Archives across the avenue. This attention on 8th Street is to help tourists find all its outdoor exhibits and sidewalk cafes, shown continuing on up to the Portrait Gallery. Four old buildings are kept for reuse to the left of the towers. The Navy's bandshell is shown to the right, embedded within the facade of a new building so that its acoustic reflector won't obstruct the square and its vistas. This location would also allow the bandshell to cast its music down 7th Street toward the Mall. It would also let people in the square turn their backs on avenue traffic and enjoy the music.

The Navy's memorial could be more than just the bandshell. It could be, as it is shown here, focused on a colossal eagle on a monumental column inscribed with major engagements. Then, particulars of naval history could be further celebrated by forming the shell's reflector into a commemorative bas-relief or mural.

Seventh Street is also to be part of the housing area. It is shown here as a bustling, active gateway to the city, as compared to the more serene path offered by 8th. That's why the sketch shows part of an historic old trolley car loop on 7th, where this connection could bring tourists into the city, just as cable cars tempt tourists to explore San Francisco. Trolleys cannot be bought with the $20 million saved by scrapping big sidewalks, but the Smithsonian could help, if it wanted to put relics of the nation's past back to work. Or the money could be found by recapturing empty monumental space at Union Station, too.

It happens that earlier planners -- those who tidied up the Mall in 1901 -- tore out 10 or 12 blocks of city in front of the station so people getting off trains would not be distracted while gazing at the Capitol. It never worked, even when tourists all came by train, because trees and Senate office buildings get in the way. Instead, pedestrians get only a lengthy walk, unrelieved by places to eat, or by places to sit, or even by real monumentality.

This area could be plugged back into the city. It could even be made more truly monumental, as well as inviting to tourists and senators alike. And making it part of the city again would bring in some $190 million, even if land here were also sold at only $350 a square foot. This is so much money -- nearly a fifth of a billion dollars -- that it could buy more than trolleys. It could help the city reopen closed clinics. It could pay off half the city's long-term debt. Or, Metro could be run out to Dulles Airport. Unfortunately, none of these projects is likely to be financed out of Union Station's forlorn foreground: Empty monumentality has always been held in greater esteen by official Washington than has running clinics or paying off debts.

Suppose, then, that Union Station's wasted land is not sold off for years to come. Suppose that delays putting in trolleys, too. A delay here would cause no real problem, as these improvements can be made almost any time. Unfortunately, Pennsylvania Avenue gives us no such leeway. All too soon, the new buildings there will all have been put up, and it will be too late to cut back on big sidewalks. Soon, too, the housing area will be finished, perhaps with too little housing to help support lively activity there, perhaps with no lure to tourists other than the back door of a bandshell, and it will be too late to consider better plans. This is the last chance for officials planning Pennsylvania Avenue to show if they have an interest in better plans, or if their corporate heart belongs only to office buildings.