Analytical Report On The Mariana Dam Disaster: Causes And Ethical Implications


Mining constitutes a significant portion of the dynamic global extractive industries that operate round the clock to procure the much-needed metals and minerals required to manufacture consumer goods essential to daily life. However, the associated risks of cave-ins, floods, explosions, leaks and myriad other hazards to public safety have made it an industry fraught with peril. Now regarded as the worst socio-environmental catastrophe in Brazil, the infamous failure of the Fundao iron ore tailings dam on 5th November 2015 illustrates how lapses in safety measures and regulatory oversight in the sector could lead to disaster. This report will analyse this event and its causes, and explore an ethical implication relevant to the case.


The Fundao dam was one of three tailing dams in a complex mining facility owned by Samarco in Mariana, Minas Gerais. Its collapse triggered a mudflow containing over 50 million cubic metres of toxic mining waste that submerged the nearby village of Bento Rodrigues prior to its entry into the Rio Doce river and eventual discharge into the Atlantic Ocean, leaving 19 dead and hundreds displaced. The ensuing investigative reports identified numerous contributory causes, including but not limited to poor impoundment control, intensified tailing deposition, substandard regulations, negligence, unethical management, and controversially, the series of three minor earthquakes recorded 90 minutes before the failure that Samarco held primarily responsible.

The final technical report attributed the failure to a chain of events starting with modifications in the initial design implemented in 2009. The Fundao dam was designed to collect two forms of tailings generated by mining operations, namely the free-draining coarse sand tailings and the finer clay-like slimes that present little permeability. The divergent physical characteristics of sands and slimes necessitate their separation to maintain appropriate drainage as the former facilitates water percolation while the latter impedes it. This partition was accomplished in the original design through selective deposition of sand and slimes behind two separate dikes with sand collected in the dike downstream forming an insulating beach. Additionally, base drains and drainage galleries under the beach facilitated the removal of water draining down through the sands, deterring critical levels of sand saturation. However, the intended design implementation was shelved as the base drains, deemed irreparably damaged owing to construction defects, had to be sealed and replaced by a less efficient drainage system, incorporating higher degrees of saturation than initially envisioned.

Restoration works on the main gallery in 2011 introduced additional complications as it prompted the opening of an overflow channel between the two dikes to admit the water over the slimes into the secondary gallery, which inadvertently enabled the encroachment of waterborne slimes into sand zones, substantially inhibiting sand drainage. Conditions were further aggravated when structural deficiencies discovered in the secondary gallery conduit precluded any further loading atop it, prompting the embankment alignment above the conduit to be set back directly over the intruding slimes. The intense loading propelled the slime forwards by the process of lateral extrusion, analogous to “squeezing a tube of toothpaste” according to lead investigators. Given its non-cohesive nature, the sand grains were pulled apart by extrusion as the load concurrently expanded with the dam heightening, thus satisfying all requisites for liquefaction, a phenomenon characterized by the abrupt loss of mechanical strength in saturated materials and the emergence of liquid-like fluidity. The reservoir height required to trigger liquefaction as predicted by computational and experimental simulations presented in the final report roughly corresponded to that of the dam at the time of collapse. The incremental increase in loading generated by the earthquakes was likely to have expedited an active process and initiated the fatal flowslide.

The disproportionately high incidence of dam failures in Brazil, and the Samarco case in particular, is symptomatic of an ineffectual regulatory framework that licensed environmentally unsustainable projects and a flawed dam monitoring system that discounted adequate dam safety verification. Brazilian mining regulation lies within the purview of the critically underfunded and archaic National Department of Mineral Research (DNPM) that inspected merely 15 percent of the registered dams in the nation in 2013-14 and had never surveyed the Fundao dam after 2012. Additionally, the lack of strict and uncompromising penalties, the triviality of low fines, and the sluggish pace of legal systems served little stimulus for reformation of corporate practices. For instance, in the two decades prior to the dam failure, Samarco had been fined around 18 times for numerous, and often recurrent, environmental violations including excessive particulate emissions, dam leaks and unlicensed operation. Furthermore, structural vulnerabilities in the Fundao dam were noted in the 2013 technical report by Instituto Pristino commissioned by the Environmental Ministry. The renewal of operating licences notwithstanding the data and the massive lobbying of the gubernatorial office that oversaw the dam inspections reveal a culture of impunity in the Brazilian mining sector.

Shortcomings within public mining regulations fostered unsound self-regulation practices geared towards maximum profitability and a blatant disregard for safety, which proved to be ultimately culpable in the Samarco incident. The limitations of the legal systems were successfully exploited by Samarco as it sought to evade fines by delegitimizing authorizations of departments to impose fines, invalidating technical reports and delaying lawsuits. The crippled oversight enabled Samarco to implement cost-cutting measures while dismissing multiple engineering reports that pinpointed defects in the structural integrity of the tailings dam. One critical misstep was the alleged failure of management to adopt the potential fixes recommended by a consultant engineer who reported cracks appearing on the dam in 2014. Earlier, the Instituto Pristino report had proposed the formulation of a contingency plan to be made legally mandatory and a prerequisite for licensing; however, no such provision was incorporated in the renewal application. With no warning system in place, residents of Bento Rodrigues had to be alerted to the imminent mudflow by telephone and word of mouth. Evidently, the systemic failure to ensure protection by Samarco was unequivocally the central feature of the collapse.

Ethical Implications

A recurrent theme noted to underlie all pivotal moments in the Samarco case when disaster could have been averted was the disconcerting indifference to public safety as evidenced by the non-observance of technical caveats raised by professionals within governmental organizations, the company and public institutes. Although gravely understaffed, the concerned regulatory departments such as the DNPM and the state attorney general’s office were manned by engineers who were indeed aware of structural discrepancies in the dam as early as 2007; nonetheless, operation licences were granted and subsequently renewed. A more rigorous application process and high unalterable standards applied to dam monitoring could have effectively held up the issuance of licence until all precarious aspects were adequately addressed. Moreover, the impetuous repudiations of numerous red flags raised by extensive private engineering analyses proved to be consequential. Most notably, an internal risk assessment report that accurately predicted the ultimate liquefaction flowslide was overruled by Samarco in favour of cost-cutting just months before the failure. Had greater stress been laid on expert opinion within the company, the progressively degenerating situation in the dam could have been defused beforehand.

Furthermore, Samarco’s noncompliance with the formal requirements concerning contingency plans for Bento Rodrigues put forth by the non-governmental organization, Instituto Pristino had fatal ramifications. The residents of Bento were selectively excluded from the planning process as they were repeatedly assured of the dam’s safety and no emergency evacuation procedure was adopted. Samarco rightly argued that hardware such as sirens was not legally required; nevertheless, installation of adequate warning systems could have precluded civilian casualties. Ultimately, the failure to promote safety owing to the negligence of the stakeholders and the compliance of the personnel involved had led to the avoidable catastrophe.

Article 1. 1f of the WFEO Model Code of Ethics states that engineers must report “unethical engineering activity undertaken by other engineers or non-engineers”. This was applicable to several occasions in the Samarco case when the engineers’ assessments were countermanded by executive ruling in a manner that jeopardized public safety. Furthermore, engineers in Samarco, as well as the administrative sectors, were in breach of the NSPE Code of Ethics, wherein subsection 2b under Professional Obligations stipulates that engineers “shall not complete, sign, or seal plans and/or specifications that are not in conformity with applicable engineering standards”. The contravention of these guidelines and the fundamental canon which is to “hold paramount the safety, health, and welfare of the public” precipitated disastrous effects in this case.


In light of the foregoing analysis of the causes and ethical issues pertinent to the Samarco dam disaster, it may be concluded that the general inclination towards profits over strategic planning and safety within the company and related authorities was conducive to the accident. It can also be argued that on discovering variations between desired and actual performances, the engineering crew rushed to quick fixes while lacking the rigor demonstrated in the early design stages. Given the dangers within the mining sector, the absence of accidents is in itself a testament to the professionalism of the personnel involved and would require a major overhaul of mining policies and practices.

15 April 2020
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