WATER MANAGEMENT
separately for re-use in the mining process.
Following initial discussions with Anglo American to flesh out the concept, a multidisciplinary team at WSP undertook a range of concept studies and laboratory trials to develop an operational concept for HDS site design.
WSP said:“ This multi-disciplinary work drew on the company’ s global team of mining professionals, bringing in subject matter experts not only in tailings management, but also in geotechnics, hydrogeology and mine water management( including pumps and piping).”
On the basis of this early work, WSP developed the concept for a large-scale field trial.
As Anglo American had already implemented CPR at its El Soldado mine, in Chile, the site was the natural place to locate the trial. The test facility was designed by the WSP team, again drawing on the wider expertise available within the company’ s global mining group to provide project and risk management, and construction quality assurance.
As part of the trial, WSP, Anglo American and the tailings contractor developed an innovative method of sand deposition to be tested. The technique involves a hydraulic sand flinger depositing sand as a slurry directly onto the tailings storage facility to form interbedded sand blanket drains. This
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unit had a capacity of 80-90 t / h of sand placement.
This process is easily controlled and much simpler than an alternative selfpropelled cyclone-based system, which was also part of the trial and is used to form vertical sand drainage columns, WSP notes.
The company’ s analysis showed that drainage of the sand slurry is quick, with the sand returning to its baseline moisture content within 10 minutes. However, the potential for evaporative water losses with the flinger is greater than with the alternative cyclone unit.
WSP said:“ The cyclone unit – the alternative method for sand deposition being studied – is self-propelling and dewaters the sand before deposition. This generates a larger-than-expected amount of water from the cyclone overflows, which required the WSP team to quickly develop appropriate water management strategies to overcome the issue.”
Other key operational challenges relate to equipment maintenance to deliver consistent operation: for example, the need to introduce screening to reduce the risk of blockages.
Extensive on-site instrumentation for data collection provided multiple data points for expert analysis and reporting through the trial. These data points were regularly monitored and reported, with the aim of proving the feasibility of HDS at large scale.
Early results were positive, with analysis showing the initial tailings layer quickly dewaters and consolidates, achieving an average degree of saturation of around 75 %. Subsequent layer placement will impact this figure.
The El Soldado trial also demonstrated high levels of water recovery, reporting 78 % of tailings water being recycled back to the mine.
“ HDS not only offers operational benefits in terms of TSF safety and water recovery,” WSP says.“ Because it uses a cell-based approach to tailings deposition, it also facilitates a progressive approach to site closure and re-use. This ultimately allows speedier repurposing of otherwise sterilised land.”
Since the drainage systems remain in place even after closure, the risk of long-term re-saturation of the tailings and subsequent groundwater contamination risk is minimised. Long-term subsidence is also likely to be significantly reduced because consolidation occurs so quickly, again simplifying closure design.
James Purrington, Associate Director – Tailings, WSP said during a recent presentation organised by IOM3 that the trial ending in November 2024 achieved saturation levels more akin to filtered stacked tailings than that of a conventional tailings deposition method.
To gauge the results of the trial, WSP compared the numbers from the trial to other Anglo sites in similar regions. Purrington said:“ The HDS site sits within the lower portion of the scale, and this is even with some of the quite impactful aspects of the trial, such as proportion of pawn size and operational guise.”
The company also evaluated the trial against the outcomes related to three hypotheses.
In terms of water savings, Purrington said the trial managed to reduce the consumption of water per tonne of tailings even when battling some fairly significant impacts.
“ In terms of safety, the improvement was twofold,” he said.“ We decreased the impact of a breach by reducing the tails outflow potential and, through desaturation, we are reducing the likelihood of a tailings storage facility failure.”
The final point related to closure, with Purrington saying that the tailings could be“ walked on” days after the completion of deposition, with the majority of the facility able to potentially be closed in a matter of weeks –“ this is a significant improvement when compared with conventional facilities”.
Another trial is planned at El Soldado involving a 250 t / h sand placement unit, which is substantially bigger than the 80-90 t / h unit previously used.
Should this go well, it may lay the groundwork for converting an existing tailings storage facility within the Anglo American portfolio to HDS operation.
Closing the loop
Mine water challenges are no longer defined by discharge limits alone. At many operations, the issue is becoming more complex: how to manage excess water, reduce losses to tailings and maintain compliance on streams the existing plant was never designed to handle.
One of the companies closing the loop in mine water management is Clean TeQ Water, using its technologies to selectively remove
International Mining | MAY 2026