Content analysis of dam break studies for tailings dams with high damage potential in the Quadrilátero Ferrífero, Minas Gerais: technical weaknesses and proposals for improvements

Abstract

Tailings dams are civil structures that have an intrinsic potential risk of failure that, if poorly managed or neglected, can lead to severe societal, environmental, and economic damage. Studies of dam breaks make it possible to anticipate these damages and plan appropriate contingency actions for critical situations. In this context, the present work presents the analysis of 86 dam break studies of mining tailings dams in the important Brazilian mineral province called the Quadrilatero Ferrifero, or Iron Quadrilateral, in the state of Minas Gerais, Brazil. The analysis involved verifying whether the studies complied with legal requirements, met international guidelines, and addressed the minimum parameters reported as critical in the literature. We found that all studies analyzed present these components: hydrological studies, the definition of the failure mode and rupture hydrograph, and propagation of the flood wave and mapping of the effects of the rupture in the valley downstream of the dam structure. However, the dam break studies showed deficiencies, such as the weakness of the hydrological studies, lack of specific criteria on the volume of tailings that are supposed to mobilize in a possible rupture, and the failures to consistently model tailings as non-Newtonian fluids. These deficiencies found in the dam break studies present in Emergency Action Plan affect the predictive capacity of the rupture models and thus the accuracy of the flood maps they generate, negatively influencing preparation actions in an eventual emergency. In the absence of guidelines and the regulation about the minimal content of the dam breach studies, we suggest that a possibility for solving this deficiency in the short run is to have technically trained professionals from inspection and control agencies audit the content of the dam break studies.