CASE STUDY # 1
STAVA TAILINGS DAM COLLAPSE
Chapter 1 – Introduction:
1.1 History of the Event
The Stava Tailings dam collapse (also known as Val di Stava Dam Collapse) took place on July 19th, 1985 in a village named Stava near Tesero, Northern Italy. In this disaster, two tailings dams above Stava discontinued to function, resulting in 268 casualties, destruction of 63 buildings and demolishment of eight bridges. Out of the two dams, the upper one was the first one to break, that eventually led to the destruction of the lower dam. The Rio di Stava valley was approached by 180,000 cubic meters of sand, mud and water at speed as high as 90 km/h. It just did not stop here; instead, the torrent travelled further for 4.2 km and approached and entered the Avisio river. Everything in between this path was also destroyed (F. Luino and J. V. De Graff, 2012).
1.2 Tragic and Financial Loss
The dam was under the management of Prealpi Mineraria when this unfortunate event occurred (Kristina, 2017). The Stava valley disaster is known to be one of the most tragic incidents and worst industrial catastrophe in the entire world. The resultant financial loss was equal to 155 million Euros (Tosatti, 2003).
Figure 1: Before and After View of the Stava Tailings Dam Failure (Luino and De Graff, 2012).
Chapter 2 – Causes and Events Leading to the Incident:
2.1 Poor Construction and Maintenance
Many investigations were done to find the root cause of the disaster. It was revealed that the maintenance of these dams was not paid much attention to. The dam’s drainage system was rendered less effective as the pipe used in the upper dam for draining water had started to sag under the sediment’s weight. During this, the pumping of water into the dam’s reservoir did not stop, which caused immense pressure on the upper dam’s bank. According to the rule of thumb, water followed the path of least resistance, resulting into the penetration of bank and liquefaction of the soil, leading to weakening of the bank and finally failure of the dam. This water pressure was then carried on to the lower dam, which also collapsed after a short time of thirty seconds (F. Luino and J. V. De Graff, 2012).
Later, it was further revealed that the stability level of the dams was not acceptable at all, owing to the poor drainage system of the ground (Davies, 2002). It was also found out that the upper dam was inadequately steep.
Figure 2: Geographical Cause of the Disaster (Thygesen, 2017)
According to the expert team that was appointed at that time to look into this matter (Causes – Fondazione Stava 1985 Onlus, 2019), the dams were built on an area that contained marshy soil due to which, the settlement of silt was impossible. In addition to this, the height of the upper basin’s bank was relatively high, i.e. 34 meters and the inclination angle was measured to be 40 degrees (80%) which were also very high. Another factor responsible for the collapse was the decision of growing the bank as per the upstream method. Although the upstream method is the swiftest and cheap, it is also known to be the most unsafe method. Moreover, for over a period of twenty years, no safety checks were ensured for the dam by the regulatory authorities.
2.1 Legal Action Against the Responsible Individuals
In June 1992, legal action was taken against the culprits responsible for the huge incident, and a total of ten people were sent to jail (Davies, 2002). This was done due to their inexpert and inadequate calculations while planning and construction of these dams.
Chapter 3 – Measures to Prevent Incident and Lessons Learnt
The unfortunate incident did occur but, to avoid such mishaps in future, there were some lessons learnt that could aid in devising measures to prevent such incidents.
3.1 Requirement of Rules and Regulations
The first step that could be taken to avoid such damage is the presence of defined regulations consisting of standards of construction, repeated inspection and operational monitoring. In order to limit and avoid the harsh consequences of tailings dam failures, there is a need for comprehensive legislation. This can be made possible by creating a regulatory check to ensure the well-being and safety of the area under consideration, also achieving financial profits of mining operations (F. Luino and J. V. De Graff, 2012).
- Management of Mineral Processed Waste
A foundation has been formed in regard of Stava incident that targets the promotion of initiatives and programs that include the involvement of technical stakeholders and public opinion, to make use of the best available technologies (BAT) for managing mineral processed waste in a better way. This can help in ensuring the environment conservation and safety of the population of that particular area (Kossoff, 2014).
3.2.1 Forced Filtration Method
One of the famous methods, although not very common due to its high price, to deal with mining waste is forced filtration. In this method, filter presses, disk filters, belt filters or drum filters are used for the separation of tailings’ two phases. The result is the complete recycling and recovery of water, and the resulting mud is hauled with trucks and front-end loader machines. This method prevents dangerous disposal structures. Also, less soil area is occupied, contaminants are managed and controlled in a better way, and filter cake (dried mud) is stockpiled for reprocessing and recycling (Rose, 2012).
3.2.2 Conversion of Tailings
The conversion of tailings can also be done by using them as the foundation of civil engineering, depending upon the circular economy’s principles. This method can help in reducing the requirement of sites of mineral waste disposal and the danger of them collapsing can also be catered. For the recovery of essential elements, the tailings can be reprocessed, truncate environmental pollution (Boaretto, 2018).
3.2.3 Planning by Technically Qualified Individual
The European Union implemented a directive related to the mineral waste management in 2006, according to which, an adequate intervention of the member states is required so that the construction of reservoirs for storing tailings is done properly and their maintenance is carried out in the right way. As directed by the EU, it is the responsibility of technically qualified individuals to manage, locate and plan these structures in a technically sound manner (Boaretto, 2018).
Chapter 4 – Conclusion
The disaster in Stava took place because of the negligence of the experts during the construction of those dams, while it could easily be avoided if proper calculations were made and geographical aspects of that area were taken into account. The only solution to avoid such a hazard in future is to consult the best experts who are technically sound and monitor their work and performance on a regular basis. By careful observation and implementation, better ways can be carved out.
REFERENCES
Boaretto, M., 2018. The Stava Valley Tailings Dams Disaster: A Reference Point for the Prevention of Severe Mine Incidents. Journal of Environmental Science and Engineering, [online] 7, pp.234-241. Available from: https://pdfs.semanticscholar.org/0b43/5171897b8bae39da66a0f9603a72cb641b54.pdf [Accessed 28 October 2020].
Davies, M. 2002. Tailings Impoundment Failures: Are Geotechnical Engineers Listening? Waste Geotechnics. 20. 1-36.
Kossoff, D., Dubbin, W. E., Alfredsson, M., Edwards, S. J., Macklin, M. G., & Hudson-Edwards, K. A. 2014. “Mine Tailings Dams: Characteristics, Failure, Environmental Impacts, and Remediation.” Applied Geochemistry. 51. 10.1016/j.apgeochem.2014.09.010.
Luino, F., & J. V. De Graff. 2012. “The Stava mudflow of 19 July 1985 (Northern Italy): a disaster that effective regulation might have prevented” (PDF). Natural Hazards and Earth System Sciences. Copernicus Publications. 12: 1030–1042. doi:10.5194/nhess-12-1029-2012.
Rose, F. 2012. Karara Iron Ore Project, Australia. Western Australian Environmental Protection Authority and State Government, Perth.
Stava1985.it. 2019. Causes – Fondazione Stava 1985 Onlus. [online]. Available from: https://www.stava1985.it/causes/?lang=en [Accessed 28 October 2020].
Thygesen, K. 2017. Val Di Stava Dam Collapse | GRID-Arendal. [online] Grida.no. Available from: https://www.grida.no/resources/11426 [Accessed 28 October 2020].
Tosatti, G. 2003. A review of scientific contributions on the Stava valley disaster (Eastern Italian Alps), 19th July 1985.
CASE STUDY # 2
ABERFAN MINE DISASTER (WALES)
Chapter 1 – Introduction:
- History of the Event
The Aberfan disaster, that took place on October 21st, 1966 in Wales, was basically a coal mine spoil tip collapse. The creation of this tip occurred in the Aberfan village, on a mountain slope near Merthyr Tydfil, covered with a natural spring. Things seemed normal until the tip started to fill with water due to excessive rain, leading it to descend down the hill in the form of slurry (McLean, 2017).
Above Aberfan, there existed a total of seven spoil tips, out of which, the tip that faced the unfortunate event and entered the village masses was the seventh tip. The height of this tip, started in 1958, was 34 meters (111 feet). According to an official report by NCB, the emergence of water springs was observed from the tip, a part of which was ground based (Edwards, 2016). The saturation of this tip took place three weeks after it rained heavily. Consequently, the amount of soil that descended the hill and reached Pantglas was around 1,40,000 cubic yards (1,10,000 cubic meters).
1.2 Tragic and Financial Loss
As a result of this tragic incident, a total of 28 adults and 116 children were killed as several buildings and Pantglas junior school was affected by it (McLean, 2017). At the school, five teachers and 109 children died as a consequence of the disaster. The number of casualties were 144 in total. To overcome the financial loss, an amount of 150,000 pounds was announced in the form of a relief fund which was also not paid to the village. However, it had been announced in the year 1997 that the remaining fund would be paid to Aberfan (Brown, 1997).
Figure 3: Aberfan after the Disaster (McLean, 2017)
Chapter 2 – Causes and Events Leading to the Incident:
It has been reported that the NCB was not totally unaware of the threat caused by the tip as a number of complaints were reported to the organization by the village. Moreover, a petition was also filed by Pantglas school in the village. Since coal was an essential requirement of the villagers at that time for domestic heating, tailings and waste materials were left behind after the process of washing. This waste was collected and dumped on the valley’s top with the help of rail trams. Although, wales had a number of tips the 7th tip was a major concern as it had reached a dangerous level of height. Even three years prior to the occurrence of this event, the tip had given a warning sign by slipping through a crater at its top (Petley, 2016). The formation of a bulge was observed at its foot since the spring water with a bad drainage system, forced the spoil to be liquefied in the form of quicksand (black in colour and thick in nature). This alarming situation did not move NCB at all, and they continued to ignore the complaints, the reason being the dependency on coal for living and employment opportunities (Aberfan, 2020).
2.1 Legal Action Against the Responsible Individuals
According to experts of that era and an inquiry that followed later, the National Coal Board (NCB) was responsible for the safety of that tip. Hence, the organization, including its total of nine employees, was held answerable for the issue (McLean, 2017).
Under the supervision of Lord Justice Edmund Davies, an official inquiry was launched, and a report was generated. According to this report, NCB was held responsible for the disaster. When the matter was further investigated, it was found out that the chairman of that organization, Mr Lord Robens, made inadequate, unclear and misleading statements and did not inform about the presence of water springs near hillside. However, the organization and its employees were not prosecuted, and no fine was charged for compensation of the loss (Jordana, 2004).
Chapter 3 – Measures to Prevent Incident and Lessons Learnt
The incident could have been prevented if suitable measures were taken at the right time. According to civil engineering experts, the lessons learned and the adequate measures to avoid such havoc are as under (Huw, 2016):
3.1 Requirement of Adequate Standards of Legislation
If NCB had acted responsibly during that time, many families would not have lost their loved ones. In light of this event, it is inferred that there is a need for suitable practice codes, standards and legislation is always there. A regular check of rules and regulations and their upgradation is mandatory for safe operation in an area. It should be ensured that the designed schemes guarantee safety and sustainability. Moreover, experts should perform targeted research in order to raise awareness, warn about any hazard and confirm regulation.
3.2 Appointment of Experienced and Qualified Professionals Only
The people appointed in organizations like NCB should always be best in their fields, with sound knowledge of all geological aspects. All the staff, including management, civil engineers, designers and inspection authorities should be carefully selected so that such events can be avoided.
- Feedback System
The lessons that are grasped and learned from a bad experience should never be ignored. Rather, they should be used as feedback for future projects, and all the chances of risk must be eliminated with the help of lessons learnt. The future engineers should also be taught about the occurrences in past so that they do not repeat the same mistakes again.
- Strict Penalties Against Ignorant Corporations
The authorities appointed for the safety of the nation or a village should be taken under a stern hand if they do not perform their duties well. No criminal should be set free so that future generations realize the cost of negligence and ignorance. Nobody should be exempt from the penalties in any case (Summerfield, 2005).
Chapter 4 – Conclusion
The Aberfan mine disaster in Wales was a result of pure negligence. Even though coal was an important asset for financial growth, daily usage and employment opportunities, its waste should never have been piled up to such a height that a series of rain turned it into a complete disaster. The planning and management of an area should be done in such a way that the waste management authorities come up with their best plans and common man’s life safe in the hands of such authorities.
REFERENCES
McLean, Iain. “Books About Aberfan”. Nuffield College, University of Oxford. Retrieved 12 September 2017.
Edwards, Huw (16 October 2016). “Aberfan was a man-made disaster. 50 years on, we must remember this”. The Sunday Telegraph.
Jordana, Jacint; Levi-Faur, David (2004). The Politics of Regulation: Institutions and Regulatory Reforms for the Age of Governance. Cheltenham, Glos: Edward Elgar Publishing. ISBN 978-1-84542-067-3.
Bbc.co.uk. 2020. Aberfan. [online] Available at: <https://www.bbc.co.uk/news/resources/idt-150d11df-c541-44a9-9332-560a19828c47> [Accessed 30 October 2020].
Petley, D., 2016. The Aberfan Disaster: A Simple Guide To What Happened. [online] The Landslide Blog. Available at: <https://blogs.agu.org/landslideblog/2016/10/17/aberfan-disaster-1/> [Accessed 30 October 2020].
Edwards, H., 2016. Aberfan Disaster – Lessons Learned. [online] Institution of Civil Engineers (ICE). Available at: <https://www.ice.org.uk/what-is-civil-engineering/what-do-civil-engineers-do/aberfan-disaster-lessons-learnt> [Accessed 30 October 2020].
Summerfield, D., 2005. “Disaster mental health”: lessons from Aberfan. BMJ, 330(7485), pp.254.2.
Brown, C., 1997. Aberfan To Be Repaid Pounds 150,000 Taken From Disaster Fund. [online] The Independent. Available at: <https://www.independent.co.uk/news/uk/politics/aberfan-to-be-repaid-pounds-150000-taken-from-disaster-fund-1243121.html> [Accessed 30 October 2020].