Global acid and metalliferous drainage management standard: BHP’s approach to reducing global acid and metalliferous drainage closure risk

Abstract

BHP operates mines across the globe that, along with providing minerals required for societal development, also generate mine waste rock. This waste rock and exposed rock surfaces could potentially result in acid and metalliferous drainage (AMD) if the operations and materials are not properly identified and managed. Because AMD can occur long beyond the operational life of a mine, AMD risk can be a key risk driver in closure cost estimates. Therefore, to address this risk, BHP has developed a global AMD management standard to be implemented across all BHP's functions and operations, including closed sites. The purpose of the AMD management standard is to provide a management framework to support consistent, simple and sustainable global management of AMD risks. This in turn is designed to assist the reduction of uncertainty in closure cost estimates. Compliance to the AMD management standard informs several elements of BHP's closure management process, specifically baseline data and knowledge, risk assessment and ongoing implementation and review of Closure Management Plans. The AMD management framework, from which the standard is based, was adapted from industry bestpractice guidance to ensure its applicability to multiple regions and commodities. The AMD Management Framework consists of sequential requirements throughout the mining lifecycle from early mine studies, mine planning, mine development and operations, through to closure and throughout post-closure. The framework is iterative with an adaptive management approach designed to incorporate new data/information and management opportunities into AMD risk assessments and mine plan revisions. To promote the effective implementation and adoption of the standard, interactive consultation was undertaken with various groups across BHP's assets. This early consultation enabled key concerns to be raised and addressed, which is designed at promoting ownership of the AMD management standard. This paper discusses the framework to which BHP's AMD management standard is based and provides an outline for its planned implementation.