Chapter 6

6. Prevention and Mitigation
Last Update: May 2012

GARD Guide Chapter 6

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Prevention of ARD is the key to avoid costly mitigation. The primary goal of the prevention is to stop contaminated drainage from leaving the mine site at its source by minimizing reaction rates, leaching, and the subsequent migration of weathering products from mine waste to the environment. The fundamental principle of ARD prevention is to apply a planning and design process to prevent, inhibit, retard, or stop the hydrological, chemical, physical, or microbiological processes that may result in impacts to water resources. A typical objective for ARD mitigation and control is to satisfy environmental criteria using the most cost-effective technique.

It is important to recognize that the science and engineering of ARD management, especially related to prevention and mitigation, are evolving. There are no off-the-shelf solutions that can be applied at all sites that will guarantee acceptable water quality through prevention of ARD or leaching of soluble constituents from mine rock, tailings or other mine materials. Therefore, the planning for and management of mine material handling and storage should be considered in a risk-based framework.

The most recent and widely accepted methods for the prevention and mitigation of ARD are presented in this chapter. The principles and objectives for prevention and mitigation are discussed as well as the suitability and applications of prevention/mitigation techniques, expectations and limitations. Examples and case histories are provided to assist the reader in understanding approaches to prevention and mitigation strategies that have been applied and for which performance data are available.

Table of Contents

  • 6.0 Prevention and Mitigation
  • 6.1 Introduction
  • 6.2 Goals and Objectives of Prevention and Mitigation
  • 6.3 Approach to Acid Rock Drainage Prevention and Mitigation
  • 6.4 Drivers of Acid Rock Drainage
    • 6.4.1 Physical Factors
    • 6.4.2 Geochemical Weathering Processes
    • 6.4.3 Climate and Physical Environment
  • 6.5 Phased Approach
  • 6.6 Overview of Best Practice Methods
    • 6.6.1 Avoidance
    • 6.6.2 Re-mining
    • 6.6.3 Special Handling Methods
    • 6.6.4 Additions and Amendment Methods
    • 6.6.5 Water Management Methods
    • 6.6.6 Engineered Barriers
    • 6.6.7 Water Cover Methods
    • 6.6.8 Drained Tailings Deposition Methods
  • 6.7 Selection and Evaluation of Alternatives
  • 6.8 Design and Construction Considerations
  • 6.9 Maintenance and Monitoring Considerations
  • 6.10 References
  • List of Tables
  • List Figures