A century ago, the Gleno Dam collapsed: the story of a forgotten catastrophe

Monumental work and symbol of progress, built with innovative technology but shoddy materials, its collapse brought the apocalypse to the Bergamo valleys.

È venuta giù la diga (the dam came down): this is the title of a ballad that four musicians – Cristina Donà, Omar Pedrini, Giorgio Cordini and Enrico Bollero – wrote together this past summer in front of the majestic “ruins” of the Gleno Dam, exactly 100 years after its collapse. In 1923, a few weeks after its inauguration, the dam gave out and swamped the valley below causing hundreds of dead and swallowing entire towns, leaving behind only death and destruction.

Much less known than the Vajont tragedy, the Gleno disaster was just as shocking for its catastrophic consequences and it is still today, a century later, an emblematic example of how progress often wavers between creation and destruction and how architecture and engineering can produce artefacts of solemn beauty but, at the same time – due to human ignorance and negligence – of lethal destructiveness.  

The Gleno Dam was built starting in 1919 in upper Val di Scalve, in the province of Bergamo, not too far from the towns of Schilpario and Vilminore. It was supposed to supply electricity and motive power to the textile factories below, within the great effort towards modernization that Italy was going through after the devastation of the Great War and the Spanish flu epidemic that in just a few months caused over 600,000 victims, almost the 1.5% of the Italian population. The dam – as reported in the newspapers of the time – has the characteristics of a cyclopean building: built at 1,500 meters above sea level, convex in respect to the head of the valley, 260-meter long and 30-meter thick, according to its designers’ intentions it was supposed to contain six million cubic meters of water, collected in an artificial lake that stretched over and area of 400,000 square meters.

It was the first time that a mixed building technique was employed: the base of the dam was realized using the “gravity method,” by placing enormous weights one on top of the other, while the upper part was build using the multiple arch dam system: an undoubtedly innovative technique but compromised – as it indeed happened – by human incompetence and greed.

Photo by Silvana Annicchiarico

In order to save time and money, the construction company used substandard materials, using lime mortar instead of concrete, rusty iron leftover from the war instead new iron, and it underestimated the leakage of water that manifested right from the start at the base of the dam. In October, due to heavy rainfalls, the basin started to fill for the first time and the leakage of water became alarming, but nobody did anything about it.

On December 1st, 1923, shortly after 7, the dam suddenly collapsed and six million cubic meters of water, mud, and debris gushed down the valley devastating everything they found on their way, reaching all the way to Lake Iseo. Some hydroelectric power plants at the bottom of the valley were swept away producing short circuits that crackled on the surface of the body of water.

Photo by Silvana Annicchiarico

The few survivors talked about it as the apocalypse, the priest of a town district, whose house was just above the furious course of the water, told the journalists that he thought he was witnessing the end of the world. The incident has an incredibly powerful echo in the weeks and months immediately after the disaster, but not too long after that it was gradually silenced, not to disrupt the optimism and faith in the “magnificent fate” of a country that had just entered a twenty-year-long Fascist era.

Today, a century after the tragedy, the ruins of that dam still stand solemn and somber, keeping the memory of what happened alive: if you hike up the path that starts in Pianezza, after about an hour walk, you can start seeing it, haughty just like the mountains encasing it, miserable and mournful, but still capable of giving you chills for how its impressiveness, its creative design and impulse, capsized into something completely opposite and became a death trap.

Photo by Silvana Annicchiarico

Opening image: Photo by Etienne via wikimedia commons

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