Tesero dam breach
At Tesero in Val di Stava (or Val di Fiemme / Fleimstal ) in the Italian region of Trentino-South Tyrol , the dam of a sedimentation basin of a mine broke on July 19, 1985 and caused a tidal wave that, according to official information, killed 268 people.
Settling basin
Two basins were at different heights, one above the other or one behind the other. They served as sedimentation basins for the landfill of the Prestavel mine of the Fluormine mining company.
The dams in these basins were more than 20 years old. The upper dam was 34 meters high and the embankment slope reached 80% (40 °). The foundation joint had a slope of 25%. In 1975 the dam systems were examined and the upper dam in particular was classified as unstable and unsafe. The safety factors were extremely low.
The causes of the failure are a damaged drainage pipe in the dam that had not been properly repaired, as well as the lack of stability of the sand dam, as the sand was soaked with water and thus became unstable. In addition, there were unusually large amounts of rain and meltwater that overloaded the upper reservoir.
catastrophe
On July 19, 1985, at 12:22:55 p.m., the upper dam broke, fell into the lower basin, and caused the dam to also break. A tidal wave of 180,000 to 200,000 m³ of mud, sand and water initially flowed at 30 km / h along the Rio di Stava (Stava brook) to Stava and then at 90 km / h down to the valley of the Avisio river down to Tesero. Another 40,000 to 50,000 m³ of earth, building rubble and uprooted trees were swept away. Everything on the way of the tidal wave was destroyed. According to various reports, there were 200, 261, 264, 268, 269 or 361 deaths in the tourist town of Tesero, the number officially reported by the Stava Foundation is 268.
Furthermore, three hotels, 53 houses, six industrial buildings and eight bridges were destroyed and nine other buildings were badly damaged.
The mud layer was 20 to 40 cm thick and extended over a length of 4.2 km over an area of 435,000 m².
The amount of damage is specified at 155 million euros.
process
After the break there was a criminal trial that lasted until 1992. Ten people were convicted of manslaughter , including the managers of the mine and those responsible for the construction and operation of the facilities, as well as those responsible for the regulatory authorities of the autonomous province of Trentino. The damage had to be borne by the operating companies and the provincial government. The last civil suits were not closed until 1999.
In addition, the judges noted that only a tenth of the legal costs would have been required to properly repair the dam after its safety flaws became known during the 1975 investigation.