Stava Tailings Dam Engineering Disaster: Research Study

This research study on was conducted in order to evaluate what parts of certain incidents or disasters were caused by engineering flaws. In July 19, 1985, a tailings dam located near the small village of Stava in Northern Italy collapsed, causing catastrophic consequences. In order to find out what engineering faults were made that led to the disastrous events, previous academic researches on the said historical incident were reviewed. The dam, built on the year 1961, was situated on a steep slope on the Stava valley, just a few hundred meters upstream the village of Stava. As mentioned above, the dam collapsed, unleashing enormous amounts of mining byproducts, claiming the lives of hundreds, as well as causing grave damage to everything that came on its path. After numerous studies, it was concluded that the collapse was caused by: the unsuitable and unstable location of the infrastructure, neglect of the maintenance of the dam, and as well as improper construction of some of its parts. These indeed prove that the disaster was caused by engineering mistakes. In the end, 10 people were convicted and ruled guilty, having to be responsible for the aforementioned mishaps. The Stava 1985 was also then founded, aiming to make public institutions and industrial operators aware of the importance of creating new strategies to prevent future disasters. This incident is also often referenced to and reviewed in order to not make the same mistakes again when making new tailings dams.

Stava Tailings Dam Disaster

Engineering is arguably one of the most important professions in this present day and age. With the continuous construction of various infrastructures and machineries all around the world, engineers work hard to help to ensure that these facilities are built properly and correctly. Proper work ethic would also help to protect the public’s health, safety, and welfare. However, it is inevitable that there would be times where negligence or malpractice in this industry would occur, often causing grave consequences. On July 17, 1985, a tailings dam situated upstream the small village of Stava, Northern Italy, had collapsed, forever changing the lives of many. This disaster caused hundreds of people to perish, the destruction of several infrastructures, as well as serious damage to nature and the economy of Italy. Following the incident, many questions were raised. Among them was the burning question, what caused this dam to collapse? Was the collapse caused by faulty engineering? If so, what were the flaws in the engineering design that led to this disaster? And lastly, how did this incident impact the practice of engineering?

To further examine the different areas of this incident, it is a must first clarify some concepts that are basic to this issue. First, what is an engineering disaster? An engineering disaster is a catastrophe or an accident caused by things such as the improper use of engineering techniques, the use of faulty materials, ignorance, or perhaps malpractice of the engineer their self. Another important concept to know in this paper is a tailings dam. A tailings dam is where the residual water and waste rock from mining goes into for storage and decanting.

To answer the aforementioned questions, a research involving many different sources were conducted. Numerous pieces of previous academic research were also thoroughly examined. Among these were the journals ‘The Stava Mudflow of 19 July 1985 (Northern Italy): A Disaster That Effective Regulation Might Have Prevented’ by F. Lunio and J. V. De Graff, ‘The Stava Valley Tailings Dams Disaster: A Reference Point for the Prevention of Severe Mine Incidents’ by Maurizio Boaretto, Graziano Lucchi, Giovanni Tosatti and Luca Zorzi, and the article ‘July 19, 1985: the Val di Stava Dam Collapse’ by David Bressan.

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Analysis

Since the 16th century, mining activities have been carried out in the Stava valley, a quiet and picturesque location near Tesero (Trento), Northern Italy. In the early 20th century, mining for fluorite became popular because of the newfound interest of the chemical industry on the said element. Because of this, a new procedure was created in order to isolate and concentrate the fluorite more effectively, which utilizes a mixture of water, rocks, and foaming agents (Bressan, 2011). However, the downside is that this process produces large amounts of toxic and semi-liquid byproducts, which then has to be collected, stored, and dried. In 1961, In order to accommodate the large amounts of waste produced by this process, a tailings dam was constructed on a nearby slope for the storing and decanting of the byproducts (Bressan, 2011). It reached to a height of twenty-five meters, and a downstream slope of about thirty-two degrees. As the years went by, mining production significantly increased. To deal with this, a second dam was created, situated just upstream of the first one in 1969, reaching up to thirty-four meters high. Drainage pipes were also placed inside the basins in order to discharge the water outside by passing through the dams (Boaretto, Lucchi, Tosatti, & Zorzi, 2018).

On 19 July 1985, twenty-three minutes after noon, the upper basin of the dam collapsed. This caused all its contents to pour out on the lower dam, also triggering its collapse (Luino & Graff, 2012). Approximately 180,000 cubic meters of water, mud, and sand were released onto the village of Stava at a velocity approaching 90 km/h (Bressan, 2011). In a span of about four minutes, the mudflow ravaged through Stava and Tesero, before flowing into the Aviso River. With its enormous velocity and consistency, the mudflow was unfortunately able to destroy everything in its path. By the end of the calamity, it was reported that 268 people lost their lives and 100 people were injured, and the disaster is also said to have caused about 133 million euros worth of damage (Luino & Graff, 2012).

After the disaster has ensued, the government of Italy immediately sprang into action, trying to find the answer to the question, what had caused the dam to collapse? At first it was speculated that the collapse might have been caused by external forces, such as an earthquake or an explosion. However, after running several tests, it was proven that these were actually not the causes of the collapse. This means that the only reason left is an internal factor, a fault in the engineering of the basins. After much investigation, several problems were found in the dam itself. To start off, the construction of the tailings dam was planned poorly. Around the time of its construction, there was no proper urban planning in the Stava valley, so permission was easily granted for the said project. It was constructed on an area with an average inclination of 25%, that is quite unsuitable and unstable to support heavy infrastructures. Placing the dams on the top of the valley was highly appealing for the tourists aesthetically, especially with the addition of the scenic beauty of the place. Moreover, while the lower basin rested on natural grounds, it was found that the upper basin only rested on natural grounds on its sides, while its front embarkment partly rested on the sediments of the lower basin. It is also worth mentioning that the upper basin had an excessive slope of over eighty percent (Boaretto, Lucchi, Tosatti, & Zorzi, 2018). Of course, according to the laws of gravity, constructing a dam this large on that kind of position is not a very good idea, as it is a disaster waiting to happen. Second, during the past 3 years before the collapse, the dam was neglected and no efforts were made to maintain it. The hydrocyclone that separates the sand from silt was no longer moved periodically, and had caused the slow deterioration of the dam. Also, generally, during the whole life of the two tailings dams, the management was also said to be definitely inadequate, which is unknowingly one of the reasons why the dam has failed (Boaretto, Lucchi, Tosatti, & Zorzi, 2018). And lastly, a contributing factor to the disaster is the fact that some of the parts of the dam were not built correctly. For example, since the upper bank of the basin was not built correctly, drainage of the water became quite difficult. Also, since the front embarkment of the upper dam rested partially on the lower one, it slowly began to spread unsettled slime on the lower one. This made drainage more difficult, and also made the structure less stable. Drainage pipes were also installed incorrectly on the basin beds. A few months before the incident, Italy experienced heavier than usual snow and rainfall. The pressure from the excess water somehow was able bend parts of the pipes, which then caused leakages. According to reports, nothing was done to restore the pipes, therefore further disabling the excess water from draining (Boaretto, Lucchi, Tosatti, & Zorzi, 2018). In the end, 10 people were held accountable for the incident, convicted of multiple manslaughter and culpable catastrophe. The Stava 1985 Foundation was also created, aiming to make public institutions and industrial operators aware of the importance of creating new strategies to prevent future disasters. This incident is also often referenced to and reviewed in order to not make the same mistakes again when making new tailings dams (Boaretto, Lucchi, Tosatti, & Zorzi, 2018).

Conclusion

To conclude this research, the dam collapsed because of internal factors, such as the faulty engineering of the structure and as well as neglecting to maintain certain parts of the dam, deteriorating and disabling them from functioning well. The collapse was indeed caused by faulty engineering. The structure was built on unstable grounds, it was not maintained properly, and some parts of the dam were also built incorrectly. After this incident, The Stava 1985 Foundation was also created, aiming to make public institutions and industrial operators aware of the importance of creating new strategies to prevent future disasters. This incident is also often referenced to and reviewed in order to not make the same mistakes again when making new tailings dams (Boaretto, Lucchi, Tosatti, & Zorzi, 2018).

All in all, all questions were answered effectively, as numerous previous researches had made it evident that this disaster is manmade, mostly stemming from engineering mistakes. This incident further reinforces the importance of properly maintaining and building massive structures like these, as it can possibly cause disastrous consequences. Personally, I was moved when learning about this incident because it’s astonishing how a small mistake could result into a catastrophe. This helps me keep in mind that when I do become an engineer, I should do my work to the best of my abilities to ensure that everything is set correctly and efficiently.

References

1. Boaretto, M., Lucchi, G., Tosatti, G., & Zorzi, L. (2018). The Stava Valley Tailings Dams Disaster: A Reference Point for the Prevention of Severe Mine Incidents. Journal of Environmental Science and Engineering B, 7(6). doi: 10.17265/2162-5263/2018.06.005
2. Bressan, D. (2011, July 19). July 19, 1985: The Val di Stava Dam Collapse. Retrieved from https://blogs.scientificamerican.com/history-of-geology/httpblogsscientificamericancomhistory-of-geology20110719july-19-1985-the-val-di-stava-dam-collapse/
3. Luino, F., & Graff, J. V. D. (2012). The Stava Mudflow of 19 July 1985 (Northern Italy): A Disaster That Effective Regulation Might Have Prevented. Natural Hazards and Earth System Sciences, 12(4), 1029–1044. doi: 10.5194/nhess-12-1029-2012.