This month, Washington will host the 50th anniversary conference of the National Trust for Historic Preservation. The trust will be celebrating the adaptive reuse of landmark structures from across the country -- stretching from the French Quarter in New Orleans, to Ghirardelli Square in San Francisco to the Quincy Market Buildings in Boston.

In the past 50 years, preservation has gone from being a sidelight activity for a few to being a key economic generator for cities big and small, so this conference provides the perfect occasion for the trust to embrace Washington's imperiled Tariff Building, also known as the General Post Office. The Tariff Building, in the middle of Pennsylvania Quarter on 7th Street NW, is one of the most significant federally owned buildings on the National Register of Historic Places.

Construction first began on the Tariff Building in 1839, making it one of the earliest federal buildings in the city. It was designed by Robert Mills and Thomas Walker, whose work also includes the Old Treasury Building, the Patent Office and Old Post Office, the Washington Monument, the Bunker Hill Monument and work on the Capitol Building itself.

The Tariff Building is filled with neoclassical motifs -- plaster and cast-iron friezes, domed stairs, vaulted corridors, an open courtyard and solid granite, marble and masonry throughout. In 1964 it was placed on the D.C. Register of Historic Sites, and it was designated a National Historic Landmark in 1971.

But since being vacated by federal agencies in 1996, this landmark has been allowed to decay. The General Services Administration, which is responsible for the building, tentatively awarded redevelopment rights some 18 months ago, but no lease was ever signed. Whether the developer can garner the necessary financing to convert the building into a hotel, as was proposed, remains unclear, but the timetable for any refurbishing and reopening of the building now is pushed back by years.

One doesn't need to be a preservationist to see the decay that has taken hold of the Tariff Building. Patrons going to the MCI Center can see trees growing from the second story. The ornamental iron fence and balustrade surrounding the building are caving in, and the boarded-up windows and ground areas show telltale signs of water and storm-runoff damage. One can only speculate as to the condition of the roof and what may be happening to the irreplaceable plasterwork inside if the roof is leaking.

GSA needs to take some immediate steps to halt this deterioration. As any homeowner knows, the leaks first must be stopped to prevent further damage. The exterior then needs to be cleaned, repaired and protected. Most important, the building needs to be reoccupied following a renovation. GSA either needs to move forward with the proposed developer or choose another developer.

The potential loss of this building to the District would be measured not only in terms of aesthetics and history, but in terms of jobs and property and sales taxes to the local economy. If the Tariff Building is to house productive economic activity early in our new century, the GSA must act now.

-- Terrance Lynch

is executive director of the Downtown Cluster of Congregations.