Earth Dam Safety

Brumadinho Dam Collapse

by Dave

Mariana denovo! Meu Deus!  In Portuguese, this means “Mariana again, my God.”

This is in reference to the dam that collapsed in Mariana, Minas Gerais, Brazil   in November 2015,  killing 19 people, spilling 60 million cubic meters of toxic mud  and completely destroying the town of Bento Rodrigues.     There were warning signs before the collapse.   The company had hired experts, who identified problems with the dam.  But the operation company Samarco, a consortium between Vale and BHP,  did too little, too late.   The investigation of the Mariana dam collapse lead to criminal charges, fines and lawsuits.   The environmental damage stretch all the way to the mouth of the Rio Doce river, to the Atlantic Ocean.  Toxic elements found in the tailings include mercury, arsenic and lead.  See link below.

The criminal charges and lawsuits provided Value strong motivation to insure their dams were safe.   But there’s an lot about Vales’s  Brumadinho dam collapse that seems similar to Mariana.  On January 25, 2019 an earthen dam,holding back 11.7 million cubic feet of tailings  from an iron ore mine  broke and  immediately created a huge mud flow for two miles.  From video shot at the time, it was a catastrophic failure with a breach in the lower sections of the dam, leading to a total caving in of the upper sections of the dam.  Heavy rainfall is likely a contributing factor.

As of Feb 23, 177 people are confirmed dead and 133 people are considered missing.  (see Wikipedia link) Many of the victims were Vale’s employees.  The force of the flood was tremendous, overturning buses, destroying homes and hotels, and drowning their occupants.  A section of a bridge collapsed.  The mud swept over approximately a square mile of land.  It definitely could have been worse.   The mud flow veered east of the village of Vale de Cachoreira (valley of the water fall),  taking some lives but sparing others.   An alarm system failed to go off.  Vale stated this failure was unimportant, as most of the destruction occurred in a matter of seconds.

As with the Mariana disaster,  there were warning signs.   Right now, all eyes are focused on a German firm TUV SUD who performed the last safety inspection in September 2018.   There is evidence that they were reluctant to sign off on the certificate of safety,  but management in Vale pressured them.    There is a serious conflict of interest in these inspections, as Vale hires the outside firm, and pays them for the inspection.   Obviously, more direct involvement is needed from the government.   The shut down of a tailing pit, I would think, could shut down operations at a mine, so there will always be some resistance.  But two accidents of this magnitude ought to be sufficient incentives for change.

The environmental impact is still being assessed.   High mercury concentrations were found in the river below the spill after the collapse.   Metal contaminants do not decompose with time.   The will become more dilute as they flow downstream.  Unfortunately toxic elements can be concentrated in fish and other animals,  leading to real health risks.

Earth dam collapses due to mining operations have occurred in many countries, including the US, India, Italy and Japan.   The precipitating event is often heavy rainfall, but preceding this, are typically structural defects.   In the case of Brumadinho, the rain lead to a process called “liquidification” where solids in the tailings became mobile.   Clogged dam outlets may have contributed to the Brumadinho disasterer. With sifting weather patterns due to global warming,  the historical rainfall patterns may become less predictable, requiring extra measures to insure safety in all tailings pits.   Brazil has many tailing pits in worse condition than Brumadinho.   This latest disaster should be considered a wake up call to Brazil (as if Mariana wasn’t enough!).

The US has its own share of disasters.  In year 2000,  in Marin County, Kentucky,  a coal mining tailing pit failed. According to Wikipedia,  “The water supply for over 27,000 residents was contaminated. The spill was 30 times larger than the Exxon Valdez oil spill and one of the worst environmental disasters ever in the southeastern United States.”     Beyond permitting requirements, a vigilant monitoring and safety inspections, free of conflict of interest with mining operators seem essential.   Remember the saying, “What comes around, goes around.”   The next Mariana, or Brumadinho type disaster  might be in West Virginia, Michigan or Kentucky.

Stay tuned,

Dave

Links:

Mariana Dam Collapse

Wikipedia,  Brumadinho Dam Collapse

Wikipedia:  Dam failures 

Other similar dam disasters: