Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Civil and Environmental Engineering

Supervisor

Christopher Power

Abstract

Acid mine drainage (AMD) contamination associated with waste rock piles (WRPs) at mining sites is a global concern, and understanding the generation and release of AMD from these piles is highly desirable. Traditional WRP monitoring techniques involve the installation of monitoring wells and periodic core sampling; however, these approaches are invasive, expensive and can only provide data with limited spatial and temporal resolution. An attractive alternative is non-invasive geophysical techniques that can provide non-invasive and continuous information on subsurface features and processes. This thesis aims to investigate the feasibility of the spectral induced polarization (SIP) method for monitoring changes in mine waste rock characteristics. Waste rock samples were obtained from three WRPs in the Sydney Coalfield in Nova Scotia, Canada. The properties of the waste rock were extensively characterized before kinetic column leaching and humidity cell experiments were performed on the samples with simultaneous tracking by SIP. Results show that the waste rock contained very low sulfide concentrations with SIP unable to capture distinct mineralogy changes during oxidation of the sulfides. However, SIP was extremely effective in monitoring the changes in the waste rock porewater characteristics associated with metal leaching and AMD flushing. Overall, this thesis improves our understanding of the capability of SIP to track changes in waste rock, while also introducing a robust approach for future experiments on waste rock and SIP.

Summary for Lay Audience

Mining activities come with environmental consequences, including the production of unwanted waste rocks. These waste rocks are usually stored in stockpiles on the ground surface, known as waste rock piles (WRPs). Once exposed to water and air, these rocks can produce very acidic and polluted water known as acid mine drainage (AMD) that can pose a threat to the health of the environment. It is critical for environmental professionals to understand how these WRPs produce and release AMD. Usually, this understanding is obtained by drilling into the WRP to collect rock and water samples to be taken back to the laboratory for analysis. However, this is slow and expensive, and only helps us understand small parts of these very large WRPs. Geophysical techniques are available that can image the ground like an x-ray and may be able to help us monitor the waste rock. One such technique is called spectral induced polarization (SIP), which may have the ability to find changes in both the water between the rock and the rock itself but needs more research to be better understood. This thesis aims to address this by performing experiments in plastic laboratory columns where SIP is used to track waste rock that is changing as it is exposed to water and air. The results in this thesis suggest that SIP has potential to capture these changes, and with more research, it may ultimately help to understand how AMD is produced and then transported from WRPs over time.

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