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The International Network for Acid Prevention (INAP) has consolidated relevant information and produced a global acid rock drainage (ARD) guide (GARD Guide) that summarizes the best technical and management practices for industry and stakeholder use. The Guide provides a structured system to identify proven techniques for characterization, prediction, monitoring, treatment, prevention, and management of ARD. It will help industry to provide high levels of environmental protection, support government efforts in assessing and regulating mine reclamation, and enable the public to gain a higher degree of understanding of acid prevention plans and practices. This paper describes the organization and content of the internet-based GARD Guide. ARD management strategies are outlined to show GARD Guide principles in practice. Finally, the path forward for the GARD Guide is presented.

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Predictions of the potential for acid rock drainage (ARD) usually focus on assessing the probability that samples and waste units will generate contaminated leachate. The rate of ARD generation, its quantity, and the possible consequences of release are usually considered in far less detail. Such analyses are deficient and do not fully assess the risk of ARD. Risk can be quantified as the product of probability of an event occurring times consequences. The result is modified by the mitigative measures or contingency plans proposed to prevent or control the undesirable event. Several methods of risk assessment are available and might be applicable to assessing the risk of ARD. These include, qualitative assessments, "what if" analysis, point-scoring systems, failure mode and effect analysis (FMEA), and quantitative probabilistic analysis. The first three simple approaches are more appropriate for advanced exploration and mine projects, while the last two more detailed techniques could be used for existing minesites. Simple qualitative risk assessments have been used by regulatory agencies, either intentionally or unintentionally, in reviewing virtually all recent projects. The more sophisticated approaches have been applied relatively infrequently in mine assessments. Placer Dome Inc. is applying and developing several schemes for ARD analysis for all phases of mining development from exploration through closure. Risk assessments need to be applied more consistently to ensure that rational decisions are made in mine project development and that over conservative criteria are not used in project assessment. IntmducuonEvaluating and accepting risk is a necessary part of deciding to proceed with any new mining project. Risk can be defined as a triplite of three questions:• What can go wrong?• How probable is it to go wrong?• If it does go wrong, what are the consequences?Mathematically, risk is often defined as the product of probability on an event occurring times consequences. The result may be modified by developing contingency plans.In the context of Acid Rock Drainage (ARD) asessments, the above three questions could be restated as • How could ARD be formed? • How probable is it?• What are the consequences of ARD generation?The first question relates to possible sources of ARD, including ore and low grade stockpiles, underground and pit walls, waste rock dumps, leach dumps, road cuts, and borrow pits. If a prevention strategy has been defined for the project, the possible failure modes of the strategy may be examined in detail in a risk assessment.The probability of ARD is usually examined in a geochemical testing program, e.g. acid/base accounting (ABA) and kinetic testing. The ABA results are often compared with criteria, or the researcher may use his or her experience to estimate a probability of ARD generation.

The Gibraltar Mine is a large open pit copper operation located north of Williams Lake , British Columbia. Acid rock drainage ~ARD) was first discovered on the property in 1982. Since this period all drainage has been collected and pumped to the concentrator for neutralization in the lime circuit. Copper is also recovered from some of the waste rock dumps using sulfuric acid leaching followed by solvent extraction and electrowinning. The Gibraltar North project is a new ore body being considered for development. An extensive program of testing and analysis was conducted to determine the potential of the waste from the project to produce ARD and to develop mitigative measures. The quantity of potentially acid generating material was estimated in two ways. First, statistics for acid base accounting (ABA) data were used to estimate the percentage of waste rock and ore that would likely be acid generating. Second, the location of a pyrite "halo" was mapped using visual pyrite estimates and assay results; a sulfur criterion was developed to separate blocks that were potentially acid-generating. Estimates of the quantity of potentially acid generating material from the two methods were different because the ABA data base under represented the quantity of waste rock in the upper benches and over represented the quantity of waste rock in the lower benches. Results highlighted the need for careful selection of samples in ARD testing programs. The potentially acid-generating zones on the pit walls were mapped using the location of the pyrite halo. In this way the quantity and location of potentially acid and non-acid-generating walls were identified. The Gibraltar North tailing exhibited a significantly higher potential to generate ARD compared to the current tailing.Additional Key Words: acid rock drainage (ARD), acid base accounting (ABA), acid-generation estimations, neutralizing potential, pyrite halo, sulfur plots, tailing acid generation, and pit wall acid generation.