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Sub-sea disposal of tailings and associated wastes from mining operations


Mining is essential to living as we know it. Mine tailings are what is left over from the mined ore after the target metal (e.g., copper or gold) has been separated from the ore. Separation is achieved by an industrial process using physical grinding and crushing to break the ore into small particles followed by chemical extraction and flotation methods. Mine tailings are known to contain heavy metals, chemical reagents used in the separation process (e.g., cyanide from gold processing), and sulphide-bearing materials.

There are about 2,500 industrial-sized mines operating around the world. Except for a very few, these mines dispose of their mine tailings on-land, usually under water in impoundments or behind dams. However, in some cases mines will dispose of the tailings into rivers and into marine waters.

Mine tailings and the LC/LP

In May 2008 the Scientific Groups under the London Convention and Protocol considered information related to the nature of sub-sea disposal operations from a number of mines located around the world, including the likely order of contaminant inputs which may be expected to occur as a result. The Scientific Groups noted that while pipeline discharges and other land-based sources of marine pollution fell beyond the regulatory scope of the London Convention and Protocol, the discharge of such tailings may frequently fall beyond any effective international regulatory control, despite their clear potential to act as major contributors to marine environments of contaminants of concern to the Convention and Protocol.

The governing bodies under the London Convention and Protocol, having noted the general obligation under the Convention and Protocol to address all sources of marine pollution, agreed that there was a need for a more detailed assessment of such discharges, and to communicate this to other relevant fora, including UNEP’s Global Programme of Action (GPA) for Protection of the Marine Environment from Land-Based Activities.

Consequently, an International Assessment of Marine and Riverine Disposal of Mine Tailings was commissioned by the Secretariat. The report can be downloaded from the link to the right.

At their meeting in 2013 the governing bodies, having reviewed the assessment report, decided to gather further information on best practices, existing guidance, etc., and to continue their outreach to other international organization dealing with this issue, before deciding on the next possible steps.