After one of the worst mining and tailings disasters in recent memory in Canada, a new report by Earthworks and miningWatch Canada have reviewed the lessons learned
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Design“Tailings facilities, which contain the processed waste materials generated from mining metals and minerals, are failing with increased frequency and severity,” the report warns. The report calls for alternatives to wet tailings ponds or, where that is not feasible, better dam designs.
“The safest tailings facility is the one that is not built,” it states.Whenever possible, wet tailings pond dams should be avoided by using filtered tailings storage, otherwise known as dry-stack tailings, the report recommends. But there can be environmental trade-offs with filtered tailings, which are mine tailings that have been “dewatered” to create a semi-solid. They are not really dry, but more like a moist material like partially dried cement. The whole point of storing mine waste (finely ground rock left over after valuable metals have been extracted) under water in a tailings ponds is to avoid acid rock drainage, which can occur when metals in waste rock are exposed to air and then water. Acid and toxic compounds can then drain into local waterways when it rains. So, filtered tailings may avoid the loss of life and property that can result from a wet tailings pond rupture, but in regions with high precipitation, it can pose additional challenges with managing acid rock drainage. Even so, when an expert panel was struck to investigate the Mount Polley tailings pond failure, it recommended the use of filtered tailings for future mines.
“They said there’s no overriding technical impediments to more widespread use of filtered technology,” said Jan Morrill, Earthworks’ international mining campaigner. “So, yes, it does require additional engineering considerations, but the expert panel that looked directly at Mount Polley said filtered tailings should be used more widely in order to promote safety.”She added that it would be difficult to implement filtered tailings at an existing dam like Mount Polley. But for all future mines, the report recommends filtered tailings. When filtered tailings are not an option, at the very least better dam construction needs to be required by regulators, Safety First states. There are three types of designs: upstream, downstream and centreline. This refers to the orientation of the dam embankments not the physical location of the tailings pond in relation to the mine, community or lake. The upstream design is considered the least secure.
“The use of upstream dams must be banned in favour of centreline and downstream dams, which are much less vulnerable to all mechanisms of dam failure,” Safety First recommends.The Mount Polley Tailings pond was a modified centreline design.
Regulatory environment and stakeholder involvementJust last week, a report commissioned by the BC First Nations Energy and Mining Council noted that the regulatory environment around tailings ponds in B.C. have improved since the Mount Polley incident, but warns that more needs to be done to avoid future dam failures. It even suggests some mines should be shut down. The report notes there are a dozen new mine proposals in B.C. and raises particular concerns over the massive KSM mine proposal, which the report says would place a massive tailings pond dam above the Bell Irving-Nass watershed.
“While transparency of decisions by mine operators has been improved by recent regulatory reforms and stakeholders now have more access to information than in the past, more needs to be done to enable direct community involvement regarding design, management and monitoring to ensure tailings dam safety,” the report states.“But in spite of B.C.’s mine law reforms after Mount Polley, the elephant in the room still remains: should the B.C. government allow the development of new tailings dams upstream of communities and should those that currently exist be closed down?”
Originally published by BIV.
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Decipher’s Tailings solution is designed to provide you with key data and insights, enabling you to effectively monitor your TSF and your environmental obligations and compliance. Our solution can be securely accessed by industry, regulators, designers and operators involved in the management of TSFs. Decipher offers a comprehensive and functionally rich solution which combines regulatory (Compliance Management Software), mining waste management, stakeholder engagement, environmental monitoring, and environmental management system (EMS) tools to assist with tailings management:
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