By Edward Cody
Sunday, September 19, 2010; A14
IN SAINT-GERVAIS, FRANCE From time immemorial, the Tete Rousse Glacier has sparkled majestically on the slopes of Aiguille de Bionnassay, an icy symbol of the Alpine heritage that molded the culture and produced the prosperity of this mountaineering town in the shadow of Mont Blanc.
But the glacier, a 20-acre mass lying within a bowl-shaped rock formation at an altitude of nearly 10,000 feet, has suddenly turned menacing.
Partly because of global warming, a giant pocket of water has accumulated within the ice, threatening to burst out of its frozen enclosure and send a wall of water, mud, ice and rock down on the chalets of Saint-Gervais spread across the valley below.
"Nature is stronger than we are," explained the mayor of Saint-Gervais, Jean-Marc Peillex, calling on his sometimes skeptical townspeople to heed the threat. "No one can confirm the risk is imminent," he said in an announcement posted around the community, "but nor can anyone confirm that there is no risk."
As soon as experts from the National Scientific Research Center reported with certainty in mid-July that they had detected the water pocket, Peillex, acting on his own advice, set up an alarm system on the glacier, connected to sirens in Saint-Gervais. Many of the town's 5,740 inhabitants, joined by up to 25,000 visitors during summer climbing season, were assigned rallying points on high ground where they could flee if the sirens wailed.
Residents of the most exposed homes on the upper side of the valley would have only 10 minutes if the glacier walls gave way all at once, he estimated, and as many as 3,000 people could be killed if the worst scenario played out.
By August, teams of scientists with special equipment were drilling day and night into the glacier to relieve the pressure, in a $3 million operation financed by the Saint-Gervais town hall, the national government and the European Union. From some holes, the water bubbled to the surface, as if from an artesian well. Pumps were lowered into others, sucking out the trapped water.
After about four weeks of drilling, Peillex said, the scientists estimate they have reduced the pressure by about half.
But as the work progresses, the specialists have raised a new fear. The glacier reaches more deeply into the rocky pocket than previously believed; it is now estimated at more than 230 feet. By draining the water and reducing the pressure gradually, Peillex explained in an interview, the scientists worry they might weaken the walls of ice, leading to a collapse that would send the remaining water rushing out in a deadly wave.
"Here in the mountains, we don't control everything," said Rosend'al Garcia, an employee of the Mont Blanc Co. who directs hikers and climbers onto mountain trails after they alight from a little train that shuttles them up from the valley.
Nevertheless, Peillex said, local and national leaders will have to decide whether to continue at the present pace or, as the scientists have recommended, send up more equipment to accelerate the drilling and evacuate the water faster.
Using magnetic detection devices similar to the scanners that allow doctors to see within the human body, the specialists estimated the glacier had entrapped between 2.3 million and 2.8 million cubic feet of water, the equivalent of more than 20 Olympic-size swimming pools.
That is a relatively small amount here in the vastness of the Alps. But it is enough to pick up so much rock and rubble on the way down the slopes, Peillex said he has been told, that outlying suburbs of Saint-Gervais could get hit by a 90-foot wall of water-borne debris that would sweep through the lower part of town and slush on down this narrow green valley 50 miles southeast of Geneva.
In addition, more recent probes have shown only about 900,000 cubic feet of water trapped in the main pocket. The rest, according to Christian Vincent, the leading glacier specialist in the rescue operation, could be in other pockets or could be trickling from chamber to chamber in little channels that the probing equipment cannot pick up. It will have to be located and drained if Saint-Gervais is to be safe.
This is not the first time Tete Rousse has threatened Saint-Gervais. In 1892, the glacier sent down a gush of water, ice and debris that killed an estimated 192 people. Although the accumulation was different from what is happening now, Vincent told reporters, the effect of a new outpouring would be vastly greater because Saint-Gervais in 1892 was nothing more than a hamlet with a dozen scattered farmhouses.
Reacting to that disaster, the French government ordered a mine-like shaft to be dug into the glacier's side to enable scientists to monitor water accumulation inside.
But in 2007, government officials told Peillex they wanted to close it down as a cost-saving measure. Only if scientists certified that the glacier presented no danger would he sign off on the closure, Peillex recalled. His insistence led to the National Scientific Research Center investigation that eventually discovered the new water pocket, lurking far deeper than scientists had been able to monitor from the observation shaft.
Not everybody in Saint-Gervais has embraced Peillex's concern; the Tourism Office, just across the street from the town hall, tells visitors the danger has passed and was largely a concoction of sensation-seeking journalists in the first place.
"There's no danger," said Michel Montini, a hotel operator and mountain guide. "There never was any danger. Peillex's pocket of water is a pocket of hot air."