Where The Water Is Running Out...A Landmark Gets A New Lease On LifeElisabeth Malkin
Roberto Sanchez Ramirez stands on a catwalk high in the Metropolitan Cathedral's soaring vaults. "The only straight thing in this cathedral is the chandeliers," jokes Sanchez, one of the engineers supervising the 17th century landmark's rescue from collapse. To the music of a midday mass below, he points out the sagging arches and ceiling cracks that reveal the cathedral's warp.
Mexico City is sinking. Worse yet, it is sinking unevenly. Nowhere is that clearer than in the cathedral and the surrounding crooked colonial blocks built atop the Aztec city. For 150 years, engineers have been pumping water from the aquifer that supplies the city, sinking the ground 7.5 meters in the past century. Under the cathedral, the pre-Hispanic remains have compressed the soft clay so that the 127,000-metric-ton edifice settles at different rates, buckling walls, tilting columns, and pitching the floor. Water, not the infamous air pollution, is the most serious environmental issue facing the new mayor, Cuauhtemoc Cardenas, when he takes office on Dec. 5.
For a start, the 20 million people living in the city and surrounding valley are used to subsidized water and need to learn a little conservation. Water is now being pumped out of the aquifer 22 cubic meters a second faster than it is naturally replenished. Even so, the city must pump a third of its needs uphill from reservoirs as far as 150 kilometers away. Since 1994, four private companies under 10-year contracts to the city have installed some 1.05 million water meters and begun to calculate bills on usage. Next year, 240,000 more meters are set to go in. In theory, reducing subsidies should encourage households to save more--if they pay their bills. As many as half don't bother, and the city, fearing political fallout in poor neighborhoods, is loath to cut them off.
Now, the four companies--joint ventures with two British and two French partners--have started repairing the city's distribution network, where some 40% of the water is lost to leaks. "It's not a sexy thing to do," says Michael Jones, director general of Industrias del Agua de la Ciudad de Mexico, a joint venture between Britain's Severn Trent Water PLC and a Monterrey-based environmental firm, Socios Ambientales de Mexico. "It's not like building a new aqueduct." Still, conservation alone won't solve the problem. So the Interamerican Development Bank is funding a study of ways to replenish the aquifer, perhaps by diverting rainwater to the recharge zones. "All the sources of water are running out," says Jairo Sanchez, the IDB's Mexico representative. "We have to do everything possible to stop the sinking."
FLOODING. Draining wastewater is equally complicated. As the city sinks, the slope of the drainage canals flattens out, slowing the untreated flow out of the valley and raising the risk of flooding during the summer rainy season. The IDB and the Overseas Economic Cooperation Fund of Japan are helping finance a five-year, $1.04 billion wastewater treatment and drainage project. Bids for four treatment plants, including the world's biggest, should go out in early 1998.
The project will also cover open sewage canals, pump wastewater to deeper drainage channels, and improve the city's runoff. "In theory, all the elements are in place for the city to solve its water problems in 10 years," says Alain Biche, Mexico director for Lyonnaise des Eaux, which holds one of the distribution contracts with Mexican partner Bufete Industrial. Now, the city needs to put the theory into practice.
At least the cathedral's problems have been partly solved. Engineers and architects working under the government's National Arts & Culture Council decided to straighten out the building by helping the parts that were sinking more slowly to fall faster. "We decided not to fight with nature," says Sergio Zaldivar Guerra, director of the project. The team dug 32 shafts 20 meters under the cathedral and lined them with concrete. At the bottom of each shaft, workmen are threading pipes into the soil to suck up clay, creating hollows into which the earth above collapses.
When work started in 1993, the northeast corner of the cathedral was 2.4 meters higher than the southwest point. That has now been reduced by almost a full meter, and the digging should end by mid-1998. Until then, work continues in the shafts dug below the warrenlike crypt, where the ashes of the city elite are sealed behind marble plaques. The growl of engines pushing pipes deep into the mud disturbs this final resting place. But the crypt's ghosts might agree that the disruption is worth it.