From GARDGuide

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Vale do Rio Doce.jpg


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--Conrad 15:52, 8 January 2008 (EST)

Research into the process of acid rock drainage (ARD) formation and methods to minimize its impact has been conducted for over 50 years. Much progress has been made in the last 20 years through a number of research consortiums. As such, there is a considerable body of scientific and engineering guidance available on ARD already through INAP, MEND, BCARD, BC MEMPR, ADTI, ACMER, WRC, PADRE and other programs. The research however is in disparate references, not easily accessible and tends to be issue, commodity or geographical centric. INAP is interested in consolidating the information and producing a guide that would be up to date and global in scope.

The objective is to produce a Global Acid Rock Drainage Guide (GARD Guide) that would be the premier reference for the mining industry, regulators, NGO’s and the public on the subject. The Guide will address the production of contaminants from sulphide mineral oxidation that can result in ARD, neutral mine drainage (NMD) and saline mine drainage (SD).

The Guide will bring together best technical and management practices with the objective of creating a body of work with high industry and external stakeholder credibility. The Guide will cover all phases of an operation from initial discovery through to final closure (“cradle to cradle”). In that way it will assist industry in providing high levels of environmental protection, assist governments in the assessment and regulation of affairs under their jurisdiction and enable the public to have a higher degree of confidence in and understanding of acid prevention proposals and practices. Overall, the Guide will provide a structured system to categorize and catalogue new technology and understanding developed through INAP, the Global Alliance (GA) and other organizations.

The overall challenge of the GARD Guide is to identify and synthesize the best available information in order to develop a global state-of-the-art summary while at the same time outlining options for different geo- climatic environments.

Therefore the scope of the GARD Guide will be acid (rock) drainage (ARD), neutral (mine) drainage (NMD) and saline drainage (SD) where contaminants are released from solid to liquid phase by the oxidation of sulphide minerals. Neutral mine drainage will include consideration of metals in solution at near neutral pH. In general, saline drainage is often used to characterize high sulphate containing drainage without significant metal concentrations and at near neutral pH. In the GARD Guide, saline drainage will encompass drainages with elevated salinity at neutral to alkaline pH where the principle constituents are – sulphate, magnesium and calcium.

The terms ARD, NMD and Saline Drainage must be defined early in the GARD Guide to eliminate any confusion in the scope of the document. Unfortunately mine water quality does not lend itself to precise compartmentalization. However a drawing such as the following chart may assist readers to understand the breadth of drainage quality issues raised by sulphide mineral oxidation.

Drainage Types.jpg

Neutral Mine Drainage and Saline Drainage can occur together (ie. near neutral pH with elevated metals and sulphate). Management of drainage from sulphide oxidation will be discussed in the Guide generically where possible but different approaches for the different forms of drainage will be highlighted where necessary (eg. sulphate treatment approaches (RO etc.) for saline drainage).

The GARD Guide Chapter 1 will continue on from this point and include a discussion of the purpose of the guide and how to use it.