February 2012

Updated acid prevention guidelines

GARD Guide to make global implementation easier

By Richard Andrews

The International Network for Acid Prevention (INAP) is updating its wikistyle best-practices guide designed to manage acid rock drainage (ARD). Introduced in 2009, the Global Acid Rock Drainage Guide, or GARD Guide, was developed by the Melbourne-based industry group of 11 major mining companies as a world-wide reference on acid prevention.

The GARD Guide is an evolving tool,” said INAP’s technical manager Terrence Chatwin. Scheduled for completion in the first quarter of 2012, four of the 11 chapters will see revision in this new iteration: characterization, prediction, treatment and mitigation of acid rock drainage.

The GARD Guide is free and is published in a web-based format to enable global distribution and continual updating; it will soon contain extra case studies and technical tools. “The guide has been set up using wiki software and has some of the same functionality,” said Rens Verburg, principal geochemist at Golder Associates, which is responsible for upkeep of the wiki. “Anyone can read it, print it, and leave a comment. However, editing of the guide requires special access rights and usernames.” Users who would like to create accounts can contact Verburg through the site.

INAP is always actively encouraging other companies to become members,” Verburg said. Smaller companies can have input to the guide by leaving comments and contacting Golder or Terrence Chatwin directly. Changes to the guide, for example, based on comments received, are a collaborative effort between INAP and its consultants, with INAP ultimately deciding when and how changes are made.”

The ongoing updates will add to the guide’s existing best-practice case study – the Mount Milligan Mine – and some of the new material will use the existing study as a template. According to Chatwin, there will also be new studies in the “Drainage and Treatment” section detailing specific treatment methodologies.

Barrick Gold Corporation, one of INAP’s member companies, uses the GARD Guide as a key reference for project environment assessment according to Bill Upton, the company’s director of sustainable development. “The GARD Guide provides information to train and familiarize our environmental professionals as well as our mining and process engineers in these best practices,” he said. With 25 operating mines and projects across five continents, the world’s leading gold producer is syndicating the GARD Guide as part of its business development, environmental management, employee training and corporate governance programs.

At the Reko Diq open-cut project in Pakistan, Barrick used the GARD Guide to define the chemical behaviour of the various rock types in the deposit and to classify their acid generation and metal leaching potential. The chapter on characterization goes into the details of high-risk rock types, which are generally defined by sulphide content and limited acid neutralization potential. According to the guide, rock analysis is very site-specific and requires characterization by both chemical tests and weathering/leaching protocols.

Universal industry uptake of the guide is critical,” said Chatwin. And while Barrick, Rio Tinto and other majors have been instrumental in creating and implementing the guide, “If it’s adopted only by the larger operators and not the smaller ones, the whole industry’s reputation will be tarred with the same brush,” he added.

The intent of the upgrade is to improve the quality and utility of the GARD Guide for all users, whether they be large or small operators, regulators or community leaders – all mining industry stakeholders,” Chatwin explained.

The Global Acid Rock Drainage Guide is available at: www.gardguide.com
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