Water was a major component of closure work on the St. Ives gold mine in Western Australia. Stantec delivered a revision of the entire
closure plan and took on all associated technical studies. (Photo: Stantec)

“When I started in the industry in the early 2000s, water was usually treated as a resource with little inherent value,” Jim McKinley, Senior Hydrogeologist at Stantec, explained. “But now, mines are increasingly being held responsible for returning sites (including water) to a stable condition that is compatible with the surrounding environment. Mining companies must provide tangible evidence that they are managing and planning for the areas that most commonly cause legacy water issues, such as the tailings and waste rock facilities. Because water management is so closely linked with closure, the magnitude of consideration that water is being given has changed.”

McKinley said that, to put this change into perspective, if you were responsible for water management at a mine site ONLY during recovery of the resource, you would likely take a reactive approach to water management and not spend much proactive capital on planning. If instead, you were responsible for water management from the time mining began until the regulators accepted that you had returned the site to the environment, you would likely understand that if the decisions made to solve today’s water management issues do not align with the closure plan, then they are counterproductive.

“Mines often find it challenging to integrate at an early stage the various water experts that are required for a robust water management plan,” said McKinley. “In my experience, using a relatively small integrated team of surface water, groundwater, water quality, geochemistry, geotechnical engineering, and climate change experts typically has more success than hiring individual firms to cover each individual discipline, which inevitably leads to working in silos. “To exacerbate the problem, in order to avoid working in silos with large consultant teams, the operators will often hire another consultant to manage the discipline consultants. And because the mine has already contracted the biggest and best firms as the discipline consultants, the managing consultant often ends up being a smaller firm that does not have enough internal resources to understand the complex nature of water management and mine closure.”

McKinley pointed out that, while there are challenges there are also opportunities. One of the first steps in managing water well is to understand the water inventory and movement at the mine site including all the site inflows and outflows, otherwise known as the water balance. It’s unlikely that a site will have too much/little water in all places at all times so, by having a robust and well-informed water balance during operations, and predictions for how that water balance will evolve during closure, operators can better understand the times and places they will face water excesses (or shortages) and plan for them.

“Proactively anticipating and mitigating water challenges, rather than reacting to them, always provides financial and scheduling advantages,” McKinley told E&MJ. “Managing water well also requires that all stakeholders be on the same page at the beginning of the project to develop a water management plan and closure roadmap. This roadmap is an integrated plan outlining the sequence of closure activities, including water management. The first day and the last day are planned, and every step in between should have the water management plan and the closure plan in mind. Details will likely change in the multi-year span of the mine’s life, but that is the nature of the mining industry. If the mine does not adapt within the guidance of the roadmap, the site could go from having a solid closure plan to having a lot of potentially expensive and time-consuming work to do after extraction.”

Designing for Closure
Stantec not only employs the world-class experts required for mine water management, but experts that are experienced working with each other and non-water disciplines to reach water and closure goals. The company provides mine water management services through every stage of mine life. Recent projects include assisting with re-opening a closed copper mine which has allowed introduction of the ‘design for closure’ mentality. Water management support has included dewatering of the current flooded pit, design and engineering of water management facilities, and predictive simulations of operational and closure conditions.

“Stantec has also been supporting Mandalay Resources with execution of a conceptual closure plan at the Lupin Arctic gold mine, including all aspects of water management and security return support,” McKinley said. “The work has involved confirmatory studies on legacy designs and completing new designs and construction drawings as challenges arise.” Because the water management plan should be integrated with the closure plan, and the closure plan must work for centuries, both need to account for climate change. Although the site may have acted a certain way during certain climatic conditions, there is no guarantee it will act the same if there is more/less precipitation or lower/higher temperatures in the future. According to McKinley, technical teams planning for water management and closure need to work with climate change modelers early and often throughout the process. This collaboration increases the likelihood that a closure solution will be effective under varying hypothetical conditions.

“I’m currently working on closing a tailings containment area at the Lupin mine site,” he said. “The original closure plan, which was approved in the 1990s, involved encapsulation of tailings by permafrost to protect site water quality. Decades later, when the mining company was ready to execute their closure plan, site data and permafrost modeling indicated that permafrost may no longer be present at the site 100 years from now. “The mining company had to completely rethink their closure technology while concurrently closing the site. If climate change experts had been involved from the onset, the tailings closure plan would have been developed using a technology that was more robust and resilient to climate change.”

In short, appropriate design and planning of mine water management infrastructure, both during operations and closure, are critical to creating a mine site that can be returned to the environment. McKinley added: “Currently, there are too many mines that are perpetually in care and maintenance or have been inherited by the government because the original operator has walked away from the site. These sites are a reminder that not only do we need to clean up our old messes, but that we must do better next time if mining is ever going to be considered sustainable. One of the first steps in doing better is to integrate closure into all aspects of mine planning, including water management planning.”

Water Treatment and Reuse
As part of effective and sustainable planning, mine operators must also navigate increasingly stringent regulations — many of which are water-related — and declining ore grades, which impact operational water needs. Together these give rise to a set of interrelated concerns that include water availability; the need for sound water management strategies and models; compliance with stricter regulations on water quality; the need for more detailed reporting to stakeholders on water management and associated risks; and tailings management.

David Oliphant, VP of Business Development - Heavy Industry for Veolia Water Technologies North America, joined the conversation. “Mining ventures are often massive investments, and investors require assurance of water supply security to meet their needs at a viable price,” he explained. “Water can take up a significant share of a mine’s capital expenditure and operating costs. The availability, quality and cost of water are key to investment decisions, and cost-effective water usage is critical to profitability.”

A view from Canary Systems’ MLRemote wireless data logging system. (Image: Canary Systems)

Oliphant and his team have found that an increasingly attractive option for mining companies is the deployment of mobile water treatment technologies. Often considered a temporary solution where an existing plant has failed, or an unforeseen situation has arisen, mobile assets are also suited to use during planned commissioning, refurbishment or maintenance projects and for longer-term water treatment requirements, such as during decommissioning and site remediation. “For the junior mining sector in particular, one of the perennial challenges is the provision of capital,” Oliphant explained. “The nature of such a business means that when raising capital in the marketplace there is a strong focus on funding for revenue-generating equipment used in ore processing within the mill. Gaining capital expenditure for water treatment is more challenging.”

Mobile water treatment can be easily fi- nanced through the operational expenditure budget on a month-by-month basis during the construction and development phases. This also gives regulators confidence of the process when the client moves from a temporary solution to permanent. With the mobile assets proving they can meet discharge regulations, it’s easier to permit the technology for long-term operations. Also, once operations are successfully generating income, investment in permanent water treatment facilities is more manageable.

“We’re seeing more mines utilizing long-term mobile water treatment solutions,” said Oliphant. “Regulatory requirements related to mine water discharge are becoming more stringent in Canada and elsewhere. Tougher requirements for maximum total suspended solids (TSS), pH balance, or the need to remove certain constituents such as ammonia, arsenic or heavy metals mean that water treatment technologies have had to evolve and develop. As increasingly hard-to-treat wastewater demands have emerged, mobile technologies allow operators to establish and understand the process and the specific challenges associated with each application. This in turn supports the development of permanent onsite treatment facilities.”

Mine operators such as Pure Gold and Greenstone are among those who have recently employed mobile water treatment options to supplement their mine sites. “In the case of Pure Gold, they have installed a hybrid system that includes a permanent AnoxKaldnes moving bed biofilm reactor (MBBR) for the reduction of ammonia and other nitrifying contributors, while using mobile assets for the removal of heavy metals and TSS,” Oliphant explained. “For Greenstone, Veolia is utilizing mobile assets for the removal of heavy metals and arsenic from historic mine workings while a permanent system is being built on-site. Once the permanent plant is completed, the mobile assets will be removed, refurbished, and ready for the next project application.”

Veolia is also developing a new, patent- pending treatment process for removal of selenium called Tracer Se, which combines biological and physio-chemical processes. The method is based on the biological reduction of selenium to selenite, its subsequent removal from water using surface complexation on ferric oxy-hydroxide, and further biological oxidation of the treated water. While the development is still in the early phases, preliminary results have shown that there is potential for excellent performance, both in terms of lowering total selenium concentration and that of known bioavailable (toxic) organo- selenium forms in the treated water.

“Good water management can be positive in so many ways,” Oliphant concluded. “It helps make a mining company attractive to investors and is a boon in obtaining access to water resources. Employees prefer mining companies that pay attention to issues such as water quality control, making it easier to recruit and retain staff. Similarly, a company practicing strong water management is viewed positively by the local community. Risks related to inadequate water management in mining are not limited to operational risks; they also have strategic implications for mining companies, such as loss of investment and damage to a company’s social license to operate.”

Monitoring and Analysis
Accurate water balance monitoring is essential to effective execution on a mine’s water management strategy over time. To learn more, E&MJ turned to data collection and integration specialist, Canary Systems.

Mining group manager, Taylor Dawn, explained: “Having the access to automated instrumentation data to allow site personnel and engineers of record (EoR) to make informed, risk management decisions is a major step in proper mine water management. We like to provide our clients with turnkey solutions for their water monitoring needs. These include working with the site and the EoRs to engineer a comprehensive monitoring solution with instrumentation and automation. We have a staff of field technicians and engineers that can install instrumentation, such as piezometers, weather stations and flowmeters to monitor both in-situ and surface water on site. After instrument installation, we install data acquisition systems, such as our flagship MLRemote data logger, to collect and transfer data to a dedicated server for data collection and processing. After the data has been collected, the site personnel can view the data within MLWeb, which is our browser-based user interface. Within MLWeb, users can cross-reference any data type, configure, and action alarms, forecast future data, and create valuable reports for water risk management.”

Dawn and her team have noted increased interest in monitoring solutions in recent years as ESG has moved up the agenda for mining companies, particularly related to tailing storage facility (TSF) management. “Canary is currently working with major, tier one mining companies to incorporate enterprise solutions for tailings monitoring at their operations around the world,” she told E&MJ. “We’re excited about these types of opportunities as they are a clear indication that these miners are continuing their efforts to be socially and environmentally conscious regarding their TSF management.”

Gone are the days of spreadsheets and manual data collection. The COVID-19 pandemic shed light on the fact that data automation and software solutions for data analytics are a must, considering many personnel transitioned to working from home, either part- or full-time. “Having a management system in place, allows for the limited staff on-site to focus more on value-add projects rather than manual data collection,” said Dawn. The Canary Systems MLRemote is a low-power, point-to-multipoint, programmable wireless data logging system. The system was specifically designed for the mining, geotechnical, structural, and environmental markets where the monitoring assets consist of numerous types of instruments, distributed over a large, difficult to access area.

“The use of proprietary communication ‘push’ technology allows for ultra-long battery life, between 3-5 years for the standard alkaline batteries, up to 10 years when using lithium cells,” Dawn added. “The unit can easily be placed in a variety of locations for long-term monitoring applications. The high-performance spread spectrum radio is available in 900MHz or 2.4GHz frequencies, and a range of up to 60 miles (100 km) is possible with the use of gain antennas and good topography. A range of up to 9 miles is easily achievable using the standard antenna and most topography. “Canary Systems has also utilized its decades of installation experience to design and fabricate a piezometer installation reel truck. The truck is fully equipped to streamline the installation process for any project with angled or grouted boreholes, as well as with singular or nested piezometer sensors.”

Remote Monitoring and Control
‘Smart’ mine water management, a term that incorporates all of the initiatives mentioned above, and more, is a ‘win win’ for mining operations’ bottom lines, as well as the local environment.

Ken Albaugh, Director of Sales and Services at Xylem joined E&MJ to discuss. “The mining industry is embracing digital technologies which make smart water management much easier,” he explained. “From remote monitoring and control (M&C) to powerful smart pumping equipment, the technology is available to support efficient water management. We always advise customers to take a holistic approach to mine water management – an efficient operation is only as good as the sum of its parts.

“Xylem offers a broad portfolio of equipment and in-depth experience in the field. We can help across all aspects of mine water management.” As well as supporting an operation’s bottom line, efficient, pumps are generally good news for sustainability. Technologies like remote M&C have the added benefit of freeing up staff to focus on other areas of the operation, and variable frequency drives (VFDs) help to ensure pumps operate as efficiently as possible.

“The pandemic highlighted how useful remote monitoring equipment, such as Xylem’s Godwin Field Smart Technology can be,” said Albaugh. “Personnel can monitor equipment remotely, removing the need for physical site visits, enhancing safety and freeing up resources for other critical tasks. This is particularly beneficial as mines today operate deeper beneath the earth’s surface, which can also be more hazardous. Digital M&C tools mean more reliability and less downtime as these technologies alert operators when a problem may be brewing.”

Xylem’s optimyze platform is a modular condition monitoring device that provides health guidance and predictive maintenance advice for rotating and fixed assets such as pumps and motors. Using predictive analysis, the technology identifies potential problems before they occur, enhancing system reliability. “It periodically monitors system vibration and temperature and allows users to access simple-to-use monitoring tools from iOS or Android mobile devices,” Albaugh explained. “This enables operators to understand the current health and historical trends of assets, create maintenance reminders and generate detailed reports. optimyze is also a useful support when commissioning a pump and troubleshooting.”

Another service that’s growing in popularity is Xylem’s water quality management and control system. This has been successfully installed in more than two dozen operations across the US, helping facility managers to ensure compliance with EPA regulations, while maintaining the safety of the surrounding area. The solution is tailor made for each customer. Combinations can include wastewater pumps and piping, monitoring sensors and pre-treatment.

Smart M&C features can also be integrated to maximize sustainability and minimize the manpower required. “Smart water management makes sense on so many levels; from optimizing productivity on site to protecting the local environment, to respecting water as a finite resource,” Albaugh concluded. “Holistic mine water management is key to optimizing efficiency, reliability and productivity on site; examining each step in the water process system helps get the most from assets and ensure optimum operation, as well as making sure that water dollars are working as hard as possible.”