Innovation in Projecting Mine Water Quality

Models Based on First Principles

Have you heard of reactive transport modelling (RTM)? 

RTM is a powerful tool for understanding and forecasting geochemistry and water quality at mine sites. First developed in the 1990s in academic and national laboratories, RTM is now a fast-emerging technique in the environmental consulting landscape.

Incorporating the geochemistry of mineral weathering reactions and the physics of water and gas flow in a fully coupled numerical modelling framework, RTM can simulate processes within a waste rock pile or tailings facility based on a first-principles approach. With RTM, we develop process-based source terms, rather than relying on empirical scaling factors, while testing our conceptual models and building a tool for testing mitigation options.

As Matt Neuner, Senior Geochemist at HydroEQ, explains, “Developing accurate estimates for a full-scale mine waste facility based on a 1 kg lab test is a big challenge. Even for mines that have operated for decades, it can be difficult. RTM helps us work out what’s actually happening within a given facility, and how those conditions and their effect on source water quality may evolve in the future, in a technically rigorous way.”

He continues, “RTM offers a leap forward in estimating source water quality – it is a better way to predict metal leaching and acid rock drainage (ML/ARD). I think that RTM has the potential to become as common as groundwater models for mine sites.” 

Image from Neuner et al. 2023 (Improving Prediction of ML/ARD with Reactive Transport Modelling; presented at BC MEND 2023).

Leaping Forward with Mineralogy

A fulsome understanding of mineralogy and mineral reactions is key to effective implementation of RTM. Traditional mineralogy methods, while still helpful, have limitations. However, as Matt notes, “With recent advances in mineralogical methods, we can now quantify, quite precisely, how metals are hosted in sulfides and other minerals.” 

Many of the mineralogy techniques needed to support effective RTM implementation are only recently becoming more widely applied in environmental contexts. As Mackenzie Bromstad, Senior Geochemist at HydroEQ, explains, “technological limitations and cost used to prevent us from applying advanced automated mineralogy techniques in ML/ARD assessments, but we now have better options available and the know-how to apply them in a fit-for-purpose way”. 

“We have newer systems with more sensitive detectors and faster operation.  Coupled with advances in sample preparation and data processing completed in collaboration with labs, we can now more accurately analyze challenging environmental materials in more cost-effective ways. Mineralogy is the bedrock of geochemical behavior, and these methods have never been more accessible to our clients.” 

She continued, “Six or seven years ago, I had a client describe a mineralogy program as a ‘Cadillac’ – today, with the advances we’ve seen, I could design a similar program for them that would be more of a “Prius” – more practical and cost-effective, easier to find, but still sufficiently advanced for the required purpose.”

Images from Bromstad et al. 2023 (Innovative Applications of Automated SEM-Based Mineralogical Analysis to Acid Rock Drainage and Metal Leaching Characterization; presented at ICARD 2022) and Neuner et al. 2023.

Looking to the future 

HydroEQ is well-equipped with our specialized in-house RTM and modern mineralogy expertise to provide targeted and tailored solutions for our mining clients. We work closely with developers of RTM software (MIN3P), and actively collaborate with experts at laboratories developing and applying advanced mineralogical methods. 

“We want to reduce the uncertainty around the risks for mine operators. These tools let us greatly improve our understanding of sources of poor water quality from mine waste,” Matt says. “We can improve geochemical conceptual models, estimates of ML/ARD, and evaluation of mitigation options.”

“Environmental success is critical for building trust in the mining industry. RTM and modern mineralogy are valuable tools to help make that happen.”