19th July 1985, 12:55 PM. Friday. In Italy, especially in the north-eastern part, when we think about an environmental disaster related to our mountains (Alps and Dolomites), the first thing that comes to our minds is the Vajont disaster.
Almost unknown is the Val di Stava disaster, in the municipality of Tesero (Trento, Northern Italy). 35 years ago, right in the middle of the summer season, 180,000 cubic meters of water and mud poured with a speed that reached 90 km/h in this small valley on the hydrographic right of the Avisio alpine river, in the middle of the Val di Fiemme.
In less than 3 minutes, the mass covered a distance of around 3 km, destroying 53 houses, 3 hotels, 6 depots and 8 bridges, in addition to uprooting trees and eroding part of the slopes. And, most of all, causing 268 deaths: all of them, except one, killed instantly. The only survivors were those who at that time were not in the village or in a hotel.
On top of the Val di Stava there was an important quarry, known as “Prestavèl mine”. Exploited since 1500, this quarry was used to mine argentiferous galena (a mineral of sulfur and lead) and, since 1934, fluorite, a mineral used to produce quality fluorine and lenses.
Fluorite is extracted by froth flotation, a process that allows the separation of the minerals from the parts that do not have economic value, thanks to a lot of water and gas. For this reason, in 1961, a plant with two tailing ponds annexed was built in Prestavèl. These ponds where two huge basins used to let the waste sludges decant.
And were these two huge basins that collapsing caused the disaster.To use the Commissione d’Inchiesta (Commission of Inquiry):
The sentenced for culpable disaster and multiple manslaughter were 10, but none of them served their prison sentence. Compensation, equal to 132 million €, were borne by the companies involved, including Montedison, Prealpi Mineraria and the Province of Trento.
Further information on the Val di Stava disaster is available on the Fondazione Stava 1985 website.