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Tailings dam risks on display

Mining majors have outlined which of their tailings dams around the world pose the highest potential risks in response to questions from ethical investors in the wake of Vale’s fatal tailings dam failure in Brazil in January.
Tailings dam risks on display Tailings dam risks on display Tailings dam risks on display Tailings dam risks on display Tailings dam risks on display

Mining majors respond to ethical investors’ request for TSF details after the Brumadinho disaster

Staff reporter

Vale said it was committed "to become the safest and most reliable mining company in the world" as it provided information, along with companies including BHP, Anglo American, Barrick Gold, Freeport-McMoRan and Glencore.

A group of 100 institutional investors, representing more than US$12 trillion assets under management and co-led by the Church of England Pensions Board and the Swedish Council on Ethics for the AP Funds, had asked 683 extractive companies to provide greater disclosure on their TSF management by June 7.

Vale outlined how it would spend $1.9 billion on decommissioning upstream dams and said its Geotechnical Monitoring Centre had started operations in February.

"Vale is going through a critical moment that has created opportunities to identify and reconfirm the company's priorities: safety, people and repair," CEO Eduardo Bartolomeo said.

The world's biggest miner, BHP, listed eight of its TSFs as having "extreme" consequences - based on the modelled, hypothetical most significant failure mode without controls, not the current physical stability of the dam, using Canadian Dam Association guidelines.

Three were at its Olympic Dam mine in South Australia, one at Whaleback at its Western Australian iron ore operations and another at a closed site in Arizona.

Two were at the stalled, Vale-operated Samarco joint venture in Brazil and the other at its Antamina joint venture in Peru.

An extreme rating means the dam failure could result in more than 100 deaths plus major environmental, infrastructure and economic damage.

Freeport-McMoRan said independent environmental management expert audits had reaffirmed the "controlled riverine tailings management system" for the Grasberg operations in Indonesia were the best site-specific management alternative.

"If any conventional tailings system had been selected and implemented, it likely would have structurally failed by now," the company said.

It said PTFI produced about 50 million metric tonnes of tailings in 2017 which used the permitted system to send the tailings down a river from the highlands to a lowlands area spanning about 230sq.km.

Barrick said two of its dams had extreme classifications, the El Liagal TSF at Pueblo Viejo in the Dominican Republic and the TSF at North Mara in Tanzania, according to the CDA and ANCOLD (Australian National Committee on Large Dams) guidelines respectively.

Glencore's extreme-rated dams included the main dam at Antamina, the main and Saddle dams at Brenda in British Columbia, and both Queaqueani at the Bolivar mine and Chilimoco at Don Diego mine at its Sinchi Wayra operations in Bolivia.

In Peru, Glencore listed two dams at its Yauliyacu mine, TSF6 at its San Cristobal mining unit, Dique 1/2 at its Carahuacra mining unit, two dams at its Andaychagua mining unit and the main dam at Cerro De Pasco mining unit, as extreme.

Glencore launched a microsite to provide details on its TSFs, and said it had appointed Klohn Crippen Berger as part of its group-wide dam integrity and safety assurance programme which was strengthened in 2016 after the Mount Polley and Fundão dam failures.

About 300 people were killed or are still missing and presumed dead after Vale's Córrego do Feijão dam at Brumadinho collapsed on January 25.