Saving Pisa's Pride

One proposal calls for supporting the famed tower with clutches of balloons held aloft by celestial cherubs. Another advocates saving the tower by building an adjacent twin structure that tilts in the opposite direction; the towers would thus prop each other like two tottering drunks. A third suggests securing the structure with a cable anchored to a mountain range ten miles away.

These and many more of the some 5,000 suggestions received to date by a government-appointed commission to save the leaning tower of Pisa are clearly frivolous. But before a bidding deadline set for this November, the committee hopes to cull as many as 100 serious engineering proposals from firms eager to try their hand at halting the continuing decline of the tower. Among the entries, commission members hope to find the solution that has eluded would-be tower savers for 800 years.

Time seems to be running short. The tilt of the tower, already more than 14 ft. from the perpendicular at the top, has recently begun increasing at 1 1/2times the normal rate.* At last count, the stresses caused by the motion have produced six major fissures in the tower's white marble and caused cracking in 94 of the 289 steps to the top. Says Ubaldo Lumini, who retired this year as Pisa's superintendent of monuments: "The tower is ill, very ill." The commission became so alarmed this summer in fact that it requested that the pumping of water from wells within a six-mile radius of the tower be stopped or severely restricted. The request was ignored by Pisans, who complained that a reduced water supply would greatly inconvenience the townspeople and local industry in the middle of a hot summer.

The tower, set on soft, waterlogged subsoil, began settling to one side soon after workmen began erecting it in 1173. As construction continued through the 13th and into the 14th century, builders tried unsuccessfully to compensate for the lean by adding a curve to the structure and putting more weight on the opposite side. Early in the 19th century, an architect tried pumping water from beneath the tower but found that this actually increased the tilt. In 1934 the government of Benito Mussolini tried a different approach; tons of cement were injected into the ground beneath the foundation. That too accelerated the rate of lean.

To spur on those who think that they can succeed where others have failed, the Italian government has promised a bonus of almost $100,000 to whoever submits the winning bid. But the terms of the competition are formidable. Bidders must be capable of carrying out the work themselves. So that the value of the tower as a tourist attraction (322,000 people climbed it last year) will not be diminished, there can be no unsightly external buttressing or more than a slight correction in the tilt.

One way often suggested to meet these requirements is to freeze the soft soil under the foundation. But engineers point out that such a move might only shift the load to lower levels of subsoil that are even softer and more likely to give way. Others, unaware of Mussolini's unsuccessful attempt, suggest injecting concrete or plastics into the ground. Then there is what seems to be the more practical plan of M.I.T. Aerospace Engineer Yao Tzi Li, who proposed ringing the tower's base with buried concrete pads. Connected to the tower by a network of trusses, the pads would in theory distribute the load over a wider area.

Whatever plan is finally picked, Livio Trevisan, director of the University of Pisa's Institute of Geology and a member of the save-the-tower committee, is convinced that quick action is needed. "Isn't it better to intervene 20 years too soon," he asks, "rather than ten minutes too late?"

* An average of one inch every 25 years.

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