Financial compensation not enough, comprehensive standards and design criteria required for tailings dams
In recent years, India has witnessed a slew of failures in tailings dams — crucial structures used by mineral processing industries and coal-based thermal power plants to dispose of their dry or semi solid waste called tailings. As India remains reliant on coal for 75 per cent of its energy generation, it is important to maintain the precarious balance between development, energy needs and environmental sustainability.
The dams, called tailing storage facilities (TSF), store various types of waste such as pond ash (a mixture of bottom ash and fly ash), bauxite residue (red mud), slag, etc. They are some of the largest structures built and their rate of failure is around 1.2 per cent — about 100 times higher than the failure of conventional water retaining dams.
Read more: Thermal power plants are still not disposing of fly ash properly, NGT cases show
About 76 significant ash pond incidents happened in Odisha, Madhya Pradesh, Chhattisgarh, Jharkhand, West Bengal, Maharashtra and Tamil Nadu between 2010 and June 2020, found a 2020 report by green initiative Community Environment Monitoring and health network Healthy Energy Initiative, India, called Coal Ash in India: A Compendium of Disasters, Environmental, and Health Risks.
The disasters surged during the COVID-19 pandemic, showed another report by Healthy Energy Initiative, India and green advocate Legal Initiative for Forest and Environment. There were 17 major incidents spanning seven states from April 2020 to March 2021, said Coal Ash in India – Vol II: An Environmental, Social, and Legal Compendium of Coal Ash Mismanagement in India.
There were three successive ash pond disasters in 2020 in Singrauli, Madhya Pradesh. Ash pond breachs release tonnes of toxic ash slurry into farmlands, villages and water ecosystems. These occurrences result in the tragic loss of human and animal lives, which has a significant impact on both their health as well as crop destruction and long-term contamination of water and soil. The Singrauli incidents led to loss of six human lives, numerous animals and contamination of environmental assets.
Despite the severity of these incidents, there is a clear lack of commitment from the industries, engineers and governance systems involved, as these keep happening on an alarmingly regular basis.
Most recently, an ash pond in a thermal power plant run by Odisha Power Generation Corporation in Odisha’s Jharsuguda district destroyed crops and polluted the Hirakud Dam reservoir on December 9, 2023. The 33-foot-wide breach spilled ash into nearby villages, water bodies and 41 farming lands and highlighted the negligence of both central and state government bodies.
Numerous such breaches have been reported, like JSW Bhusan Power and Steel Ltd’s tailing dam failure on January 20, 2022, in Thelkoloi village, Sambalpur district, Odisha. Another ash pond breach occurred in February 2022 in Chachai, Jabalpur district linked to the Amarkantak Thermal Power Station.
Read more: New MoEFCC notification on fly ash includes solar, wind power plants for reclamation
In July 2022, a breach was reported Koradi and Khaparkheda power station in Nagpur. An ash pond in Rautdih, Bokaro district in a Bokaro Power Supply Company Ltd power plant breached twice in 2022.
The previously cited 2020 compendium only scratched the surface, as numerous pond ash and other tailings failures occur on a regular basis and go unreported. Furthermore, the illegal dumping of dry tailings and pond ash continues, causing serious health consequences such as respiratory problems, skin ailments, kidney stones, airborne diseases, and widespread pollution of the air, water, and soil.
The relaxation of regulatory standards for tailings and pond ash management has enabled industries to disregard ecosystem health and public safety. A case in point is the optional status granted to coal ash washing in 2020 by the Union Ministry of Environment, Forest, and Climate Change (MoEFCC).
Another instance is MoEFCC’s extension for the deadline for 100 per cent utilisation of coal ash from 1999 to 2021.
In a 2021 report, the Centre announced an impressive 95.95 per cent utilisation of ash generated. Intriguingly, the remaining 4.05 per cent, amounting to 10.96 tonnes, still warrants attention.
Additionally, the substantial legacy ash of 1.6 billion tonnes in ponds cannot be ignored, especially as the use of coal continues to rise, leading to the continuous accumulation of this legacy ash. The MoEFCC’s most recent guidelines for coal ash, published in June 2023, recommend utilising legacy waste within ten year.
While 100 per cent utilisation is still uncertain, the term ‘utilisation’ is also concerning as it includes the filling of hazardous ash in low-lying areas, void filling without any protective measures. This happens because the ash has been removed from hazardous industrial waste category since 2000 — underscoring another instance of governmental negligence.
Notably, this ash contains heavy metals such as arsenic, mercury, molybdenum, fluoride, and cadmium, posing severe health risks to both humans and animals.
Read more: Fly Ash Management and Utilisation Mission: Will it boost handling, disposal of by-product
The National Green Tribunal has consistently directed the central government to undertake remedial measures for environmental restoration and incident prevention since 2013. While some affected individuals have received financial compensation from industries, it is questionable whether any monetary penalty genuinely equates to the environmental disasters, loss of biodiversity, air and water contamination and irreversible farmland pollution stemming from such incidents.
Though TSFs should last 40-50 years, the reported recent dam failed within 10 years of being built. The causes were a weak foundation made mostly of tailings or ash material, severe hydrostatic pressure or static liquefaction in which the tailings behaved like slurry, and operational failure, showed investigations.
In India, the Union Ministry of Mines has adhered to a tailing dam design standard established in 1995, which has not seen any subsequent updates. Central Electricity Authority further recommended ash dyke embankments conform to IS 7894: a code for the practice of stability analysis of dams.
The technical complexity arises from the heterogeneous nature of tailing materials and pond ash, which exhibit significant variations over time and are influenced by factors such as water and the surrounding environment.
The current guidelines omit any mention of fly ash toxicity. The use of a liner system to prevent groundwater contamination is also not required for High Concentration Slurry Disposal systems. Inadequate scientific and technical expertise in the use of ash and tailings, combined with flaws in the design factors for tailing dams and ash ponds, contribute to recurring incidents.
Read more: Indian states, power plants with poor ash utilisation must act now
Amidst the growing concerns surrounding the safety of tailings dams, there is a pressing need for comprehensive standards and design criteria for how these structures are conceptualised, constructed and managed. The guidelines must address tailings and pond ash behaviour, including scientific landfilling, routine monitoring methodologies, incident prevention systems, and measures to combat air and groundwater contamination.
With technological development, mathematical modelling to predict dam behaviour in extreme conditions and artificial-intelligence-based monitoring system can also be helpful to prevent environmental contamination. Additionally, these guidelines should emphasise the retrofitting of existing ash ponds with robust liner systems to ensure dam stability without compromising the ecosystem.
The MoEFCC should also implement a strong environmental policy, requiring adherence to design standards and mandating regular technical assessments overseen by relevant authorities and experts. For such accidents, criminal procedures for human loss and environmental contamination must be filed with the appropriate authorities.
Surabhi Jain is Coordinator, International Workshop on Biogeotechnics and PhD (Indian Institute of Technology, Madras); PECFAR awardee, TUM (Germany) and Postdoctoral fellow Indian Institute of Technology, Dhanbad
Views expressed are the author’s own and don’t necessarily reflect those of Down To Earth
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