After four decades in tailings management, one thing has become clear to me: the fundamentals of good design rarely change. What does change is the context—larger facilities, more challenging environments, tighter regulations, and higher expectations from communities and investors. With that in mind, I want to share the five most common mistakes I’ve seen in tailings storage facility (TSF) design, and more importantly, how to avoid them.
1. Treating the Foundation as an Afterthought
The mistake:
Too often, the focus is on the embankment itself while the foundation is given less attention. Weak foundations, unassessed permafrost, or unaccounted for collapsible soils can undermine an otherwise well-designed structure.
How to avoid it:
A TSF is only as strong as the ground it’s built on. A comprehensive site investigation—including drilling, sampling, in situ testing, and hydrogeologic assessment—should guide every design decision. Never assume the foundation will “take care of itself.” And remember my favorite adage: You never save money by having a cheap site investigation.
2. Underestimating Seepage and Water Management
The mistake:
Water is the single most important factor in TSF stability, yet many designs fail to fully account for seepage, climate variability, or adequate drainage. This often results in higher phreatic surfaces, reduced effective stress, and an increased risk of failure.
How to avoid it:
Start with a conservative water balance model that accounts for climate extremes. Design seepage control systems (drains, cutoff walls, liners, or GCLs) with redundancy. And remember: water management doesn’t stop in the design phase—it requires disciplined operations and monitoring.
3. Relying Too Heavily on “Paper Stability”
The mistake:
I’ve seen designs that “work” perfectly on paper, with slope stability analyses showing factors of safety well above minimums. Yet, those models are only as good as the assumptions behind them. Simplified inputs or optimistic parameters can give a false sense of security.
How to avoid it:
Use multiple analysis methods (limit equilibrium, finite element, probabilistic approaches). Challenge your assumptions with sensitivity testing. And above all, incorporate observational data (piezometer readings, settlement surveys, and construction performance) into your ongoing assessment of stability.
4. Ignoring the Human and Operational Factor
The mistake:
Even the best design can fail if operations don’t align with it. Deviations from the planned construction method, lack of compaction, uncontrolled raises, or poor pond management can erode the safety margins built into the design.
How to avoid it:
Design with operations in mind. Make sure the facility can be built and run by the people on the ground, with the equipment available. Clear operating manuals, training, and ongoing communication between engineers and operators are essential.
5. Failing to Design for Closure from Day One
The mistake:
Closure is often left as a problem for “future engineers” to solve. This mindset leads to facilities that are difficult and costly to close, or worse, that remain a perpetual liability.
How to avoid it:
Incorporate closure principles at the design stage: final landform, water cover or dry closure, long-term seepage control, and maintenance requirements. A facility that can be safely and affordably closed is also more resilient during operations.
Final Thoughts
Most TSF failures are not caused by a single catastrophic oversight, but by a combination of smaller mistakes—shortcuts in site investigations, optimistic assumptions about water, overreliance on models, gaps in operations, and neglect of closure. The good news is that every one of these mistakes is avoidable.
The best designs are not the most complex, but the ones that balance sound engineering, practical construction, robust monitoring, and long-term stewardship. After all, a tailings facility is not just a project—it’s a responsibility that extends well beyond the life of the mine.