 It is around 12pm on the 19th of July 1985 and it is like any other day for the village of Stava, Prento, Italy. But the average midday is interrupted with rumbling. No one knows this but the noise has come from further up the Rio de Stava valley and it's roughly 180,000 cubic metres of mud, sand and water released from two failed dams. The river would be hit with water and mud and debris at speeds of up to 56mph. The resulting loss of life would rank this day as one of the country's deadliest in peacetime. Today I am looking at the Valdes Stava Dam Collapse, my name is John and welcome to Plainly Difficult. There's Money in the Hills The area around the Stava valley has been the home to mining ever since the 16th century. The region was home to various mineral deposits. Fluorite began being exploited from 1934 in small industrial operations. But if we will fast forward to the 1960s and 1961 in particular, a new plant is being opened to better achieve higher grade fluorite. At the same time a basin was produced and a small starter dam was constructed to hold back the byproduct of the operation tailings. You see the method the plant was using was what's known as froth flotation. This method creates a greater concentration of fluorite but also tailings. Tailings are basically all of the leftover rock, sand and not required materials. They are stored in a basin where the water is decanted off and recycled and then the dry tailings then becomes the base for another layer of tailings on top. The original dam at Stava was constructed of locally sourced materials creating a gravel core. A sand shell was placed over the core, the downstream slope was raised at an angle of about 32 degrees to a final height of 25 meters. To save money the hillside was made part of the basin. By 1967 the Mont Edison Company was granted the concession to operate the mine and by extension the dam. As the industrialised mining ramped up the site would need more tailing storage. As such the mine decided to build another dam and base in just a few feet upstream from the original. The second dam was built without any real anchoring to the ground at around 1969. It was allowed to grow in size at less than an ideally controlled rate with even less than ideal drainage. Eventually the foot of the second dam will extend out to the pond section of the lower tailings dam. Just as a side note here, the water pond on top of these types of impalments are usually not allowed to get close to the dam part as it can erode the loot laid material. Water was drained via pipe work that ultimately led into the Stava River. The pipe work ran through the basins and dams and had drain holes within it. It would later be found that they did not do a pretty good job at draining, even weakening the dams during heavy rainfall by allowing water to seep out. The lower dam by 1971 ceased to be raised, leaving just the upper dam as the sole depository for tailings. In the mid 1970s the operation was transferred to a company called Flora Mine. By 1978 the second dam was towering over the lower and its use was also discontinued. Only for a few years however, when in 1982 it was put back into service. During the mine's booming use a number of residential apartments were built to house the workers coming from different parts of Italy. The site that employed improper planned dams with inadequate draining would not be a surprise to anyone in experiencing some issues with its basins and dams. In 1985 two partial failures of the site's water drainage system resulted in a partial landslip and sinkhole in the upper basin and a sinkhole in the lower basin. It was found that the pipes were poorly placed within the dams and basin, causing them to sag under the weight of the silt deposits. The two failures were repaired and the lower basin pipes were diverted. On 1985 the total height of the structure was some 60 metres and water was being pumped into the upper basin, even with the failing drainage. But what could go wrong? The Collapse It is around 20 minutes past noon on the 15th of July 1985 at a large boom erupts in the Starver Valley. Within milliseconds the upper dam and basin had failed. The weight of the tailings silted and water smashed into the lower basin. Bearing in mind that the upper dam was taller than the lower, there was no chance of the older structure being able to hold back the massive material. Almost instantly the lower dam also failed as the water seeped into the overstressed structure. The combined destructive force of both impoundments started to slide down the valley. White dust was kicked up in the air and the dam's 180,000 cubic metres flow of semi-fluid slime picked up speed, descending the valley's slopes. The reach speeds of up to 90 kilometres an hour and was hurling towards the village of Starver. In its wake some 50 houses would be destroyed, hundreds of trees would be uprooted and eight bridges demolished. The apartments built for the mine workers were also completely wiped off the map. The flow wasn't slowed down by the village and the torrent continued until it reached the Avizio River, some 4.2 kilometres or 2.6 miles away. The insuring chaos caused 268 lives to be lost, 100 people were also injured and only 8 victims would be rescued alive after an extensive search and rescue effort. Clean up and rebuilding would take many years and the true scale of the loss would take a while to sink in, but although tragic the cause had to be established. The investigation The remains of the dam and flow of debris offered some evidence on where the disaster began. It showed clearly the issue was within the dam structure. But some of the most important places to investigate were in eyewitness accounts of before, during and after the collapse. The sinkholes that appeared earlier in the year came to light and the improper rising of the second dam pointed at a maintenance and management issue. It was found that even though the drainage pipes had began to sag, water was still pumped behind the impoundment, which resulted in a weaker structure. Weight behind the dam was too much for the coarse and loose sand beach of the structure. It was found during the investigation that the dam's location was also unsuitable right from the start, with the original lower basing being constructed on steep marshy land. As we know from earlier on in the video, using a hillside saves cost on a larger impoundment. And with 1970s technicians even raised issues with the second dam, that it was on dangerous ground. However, the company continued to increase the height irrespective of the warnings. The ministerial inquiry into the disaster would conclude, the plant collapsed essentially because it was designed, built and managed in such a way as to not offer those safety margins that civil society expects from works that can jeopardize the existence of entire human communities. The upper embankment in particular was poorly founded, poorly drained, statically at limit. It could only collapse at the slightest modification to its precarious conditions of equilibrium. As such, 10 mine officials were charged with criminal negligence, culpable disaster and multiple manslaughter. And prison sentences were handed out in 1992. Starveh village was reconstructed and eventually repopulated. The land recovered, but the wounds in the local psyche would take much longer. Although some saw prison, time for their negligence, history sadly continues to repeat itself at various tailings dams across the world. This is the Plain Difficult Production. All videos on the channel are Creative Commons attribution share alike licensed. Plain Difficult Videos are produced by me, John, in the currently very sunny and warm corner of South London, UK. I have Patreon and YouTube members, so I'd like to thank you for your financial support, as well as the rest of you for tuning in every week just to watch my videos and hear me talk. I have Instagram, Twitter and a second channel made by John, and all that's left to say is thank you for watching and Mr Music, play us out please.