Abstract

The risks of inadequate and/or improper Acid Rock Drainage (ARD) and Metal Leaching (ML) characterization and subsequent management are front and center in mine development. The long legacy of ARD/ML risks in mining mean that today’s mining community understands that ARD/ML issues can result in some of the most expensive and longest lasting environmental impacts that could arise during the life of a mine. Within the mining community, it is commonly understood that ARD/ML can occur from the oxidation of disturbed (excavated) sulphide-bearing rock due to exposure to air and water over time. However, it is not only mining activities that can expose such potentially acid generating and/or ML rock. Quarrying and excavation of bedrock are common activities associated with infrastructure projects including hydroelectric dams, highways, and tunnels. The potential risks and impacts associated with ARD/ML are both lesser-known and/or understood in the infrastructure space. As such, infrastructure projects can have negative environmental and financial impacts because of the unexpected formation of ARD/ML. We review several high-profile infrastructure projects where the failure to effectively characterize ARD/ML risks during project development have resulted in an expensive legacy. We consider some of the reasons this may be happening, and what is being done about it. Historically, many jurisdictions have not provided industry standard guidelines, nor have they required any ARD/ML characterization ahead of/during/or even after the construction of infrastructure projects. Awareness of the risks associated with ARD/ML development from infrastructure project development has become more widely understood over time. In the absence of industry specific standards, proponents within the infrastructure space have relied upon existing ARD/ML characterization frameworks developed for the mining industry to evaluate the potential ARD/ML risks associated with their projects. In recent years, efforts have been made to develop infrastructure specific ARD/ML prediction programs, based on existing ARD/ML characterization frameworks developed for use in the mining industry. This a step in the right direction for non-mining related projects to evaluate ARD/ML related risks, however we must consider the applicability of utilizing these mining industry related geochemical characterization frameworks to assess infrastructure projects. Several differences exist between these industries, such as the availability of baseline information, the complexity and understanding of geological settings, and strictness of construction timelines. This discussion focuses on how existing ARD/ML characterization frameworks can be tailored to effectively characterize the geochemistry of materials from infrastructure projects. Successful ARD/ML prediction at the conceptual phase will minimize the potential for environmental impacts and escalated project costs associated with unexpected or improperly characterized ARD/ML materials.