Advances in Ensuring Tailings Dam Safety

Advances in Ensuring Tailings Dam Safety

Author: Duncan Grant-Stuart
Conference: SANCOLD Annual Conference
Date: November 3-5, 2021

ABSTRACT
Recent widely publicised and catastrophic tailings dam failures resulted in a request to 684 Mining Houses by the Church of England Pension Fund for full disclosure of the status of their Tailings Dams (or tailings storage facilities – TSF’s). The Church of England Letter, as it has come to be known, prompted the International Council on Mining and Metals (ICMM) to publish the Global Industry Standard on Tailings Management (GISTM) in August 2020. The GISTM provides a framework for safe management of Tailings Dams while allowing operators flexibility in how to achieve this goal. The ICOLD Sub-Committee L (Tailings Dams and Waste Lagoons) has prepared a new Bulletin which will be submitted to the ICOLD Central Committee in November 2021 to provide Technical Guidelines in support of the GISTM’s Management Principles.

INTRODUCTION
To a large extent tailings dams were unregulated throughout the first half of the 20th century, and inevitably the early methods of tailings dam construction led to failures with varying degrees of consequence. The introduction of legislation relating to tailings dams has primarily been driven by the occurrence of failures of these facilities. Records of tailings dam failures prior to the 1960’s are sparse, but the Aberfan coal fines dump tragedy in Wales in 1966 focussed the world’s attention on the safety of mine residue deposits and tailings dams. Southern Africa has had its share of tailings dam disasters, with the worst being listed below:

  • 1970: Mufulira in Zambia, where an inrush of tailings into underground workings resulted in 89 fatalities
  • 1974: Bafokeng Mine in the North-West Province of South Africa, where a failure of the tailings dam caused a 40km mud flow which engulfed a shaft resulting in 12 fatalities underground.
  • 1978: Arcturus in Zimbabwe, where overtopping after heavy rain resulted in one fatality and extensive environmental damage
  • 1993: Saaiplaas, in the Free State province of South Africa, where a failure resulted in the release of 140 000 m3 of tailings
  • 1994: Merriespruit, also in the Free State province of South Africa, where a failure following heavy rain resulted in 17 fatalities

Each failure of a tailings dam, and the emergence of previously unforeseen or ignored environmental impacts from tailings dams in general, has resulted in the strengthening of legislation regulating the siting, design, construction, operation, management and closure of tailings dams.

In 1978 the Chamber of Mines’ “Guideline for Environmental Protection – The Design, Operation and Closure of Metalliferous and Coal Residue Deposits” was published and provided the first structured guideline for the design and operation of tailings dams in Southern Africa. It was subsequently updated in 1983 and again in 1996.

In 1998 The South African Bureau of Standards published SABS 0286 (now SANS 10286) “Code of Practice: Mine Residue”. This document, although not legally binding or prescriptive, provides guidelines for the siting, design, construction, operation, management, surveillance and closure of tailings dams in Southern Africa.

With effect from 2001 the South African Department of Mineral Resources (DMR) requires the owner of a mine residue deposit to have a Mandatory Code of Practice for the facility. The Code of Practice documents areas of responsibility for any mine residue deposit and by law must be updated on a continual basis.

Today tailings dams in South Africa are required to be constructed and operated in accordance with several different Acts of Legislation, some of which may at times appear to be contradictory. There is no single Statute, Act or Regulation in South Africa dealing specifically with the construction, operation and decommissioning of Mine Residue facilities.

Recent amendments to the Water Act (Act 36 of 1998) and the National Environmental Management Act (Act 107 of 1998) have placed increased onus on the owners, operators and designers of tailings dams to prevent environmental degradation and ensure the safety of persons and property in their proximity.

Perhaps the legislation most pertinent to Tailings Dams is Government Notice R704 of the National Water Act dated June 1999 (commonly referred to as GN 704) which, inter alia, requires that a mine must:

  • Ensure that contaminated water must be kept separate from clean water and must not be allowed to spill into a clean water system more than once every fifty years
  • Operate any dam or tailings dam that forms part of a dirty water system to have a minimum freeboard of 0.8 metres above full supply level
  • Prevent water containing any substance which is likely to cause pollution of a water resource from entering any water resource
  • Ensure that water used in any process at a mine or activity is recycled as far as practicable

 

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