Effective Assessment of ARD/ML Potential for Non-Mining Infrastructure Projects
Author: Amber Blackwell1
Conference: 13th International Conference on Acid Rock Drainage
Date: September 16-20, 2024
1 Knight Piésold Ltd., North Bay, ON, Canada
ABSTRACT
The risks associated with 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 means 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 because of exposure to air and water over time. However, it is not only mining activities that can expose potentially acid-generating and/or ML rock. Bedrock excavation is also a common activity associated with the development of non-mining infrastructure projects, such as hydroelectric dams, highways, and tunnels.
The potential risks and impacts associated with ARD/ML are both less well-known and understood in the infrastructure space. As such, the development of infrastructure projects can result in negative environmental and financial impacts because of the unexpected formation of ARD/ML. We review several high-profile infrastructure projects that did not effectively characterize the potential ARD/ML risks during project development, resulting 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 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, with most of them building upon the existing ARD/ML characterization frameworks used in the mining industry. This is 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 the strictness of construction timelines. This discussion focuses on tailoring existing ARD/ML characterization frameworks 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.
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