Tailings Dams in Brazil
Past, present, and future risks associated with mining dams
Mining Activity in Brazil
Map of colonial roads to transport gold and diamonds in Brazil. Courtesy of Angela Ricciardi via Pinterest
Mining has been an important economic activity in Brazil since the discovery of rich mineral regions during colonial times. Portuguese settlers first discovered reserves of gold in the state of Minas Gerais in 1693, and later diamonds in 1729. Since then, mining has always been an important aspect of the Brazilian economy, especially in the state of Minas Gerais, which in translation to English means general mines.
Currently, Brazilian mining activities are centered on iron ore extraction, being the 2nd largest exporter. The country is also prominent in the extraction of copper, gold, aluminum, manganese, tin, niobium, and nickel.
Gemstones are also explored in the country, with lead exports being amethyst, topaz, agate, tourmaline, emerald, aquamarine, garnet, and opal.
Currently, industrial mining in the country resorts to tailing dams to dispose of mining byproducts that do not serve any purpose in the commercial chain or have high levels of toxicity.
Dam Construction
Tailings dams diagrams representing forms of dam construction for the disposal of industrial mining byprouct. Image 1 (left) is a courtesy of Kym Lesley Morton , and image 2 (right) retrieved from WISE Uranium Project
Diagram showing the different approaches for the construction of tailings dams. Courtesy of The Wall Street Journal and W ISE Uranium Project
Tailings dams in numbers
Currently Brazil has 911 tailings dams in operation.
The states of Minas Gerais and Pará are among the most prominent exporters of minerals. Other states such as Mato Grosso, Bahia and São Paulo also contain a large number of dams.
This graph further highlights the discrepancy in tailings dam concentration across the country.
Even within the densest tailings dams state, dams are more concentrated in the southeast portion of Minas Gerais. This region is known as Quadrilátero Ferrífero (Iron Quadrangle).
Previous Accidents
With the accumulation of byproduct deposits and climate and seismic variations, dams can failure, leading to the breakage of security walls and spill of dam contents. Tailings dams are more susceptible to accidents since they are not built of concrete. The dykes are often built out of dense compacted mud.
Past Dam Accident Sites
Mariana (2015)
Brumadinho (2019)
Both sites are also within the Iron Quadrangle.
Mariana
43.7 million cubic metres
19 deaths deaths
Brumadinho
12 million cubic meters
270 deaths
Mariana Dam failure (2015) Image 1 (left) shows the contaminated river stream flowing into the Atlantic Ocean. Image 2 shows the village of Bento Rodrigues after the event. Image 3 (right) shows the area covered by the flow of byproducts. Courtesy of IUCN Portal , CNES 2015 Distribution Airbus DS, and TV Senado.
Brumadinho dam failure (2019). Retrieved from the Wall Street Journal
Brumadinho directly affected area
Current Risks Assessment
Dams are routinely inspected and classified according to their failure risk and potential damages
Only one dam is in a critical alert stage. Four others are in stage level 3.
The terrain in the region is very intricate, full of hills, valleys, and river streams. High elevations are not present but there is high variability.
Scene presentation on regions where dams in risk of failure are located in the state of Minas Gerais. The scene viewer allow us to understand better the countours of the land and possible routes for mudflow.
