Chapter 14 — Case Histories

Purpose of this chapter

These summaries describe publicly reported lessons from significant tailings incidents at a general, factual level — what was learned about monitoring and surveillance, not proprietary detail. They are included to build engineering judgment. Always consult the official investigation reports and the applicable regulatory guidance for authoritative accounts.

14.1 Lessons shared across incidents

Reviewing major tailings failures reveals recurring themes directly relevant to this reference:

• Liquefaction of loose, saturated tailings is the dominant catastrophic mechanism, especially for upstream-construction facilities.
• Early signals were often present — rising pore pressure, movement, or changing seepage — but were not always detected, communicated, or acted upon.
• Visual surveillance and instrument data together would have revealed more than either alone.
• Consequence of failure is extreme, justifying intensive, independent monitoring for high-consequence facilities.

14.2 Illustrative examples (generalized)

Several widely cited incidents illustrate the themes of this book:

• A large upstream-facility flow failure demonstrated how static liquefaction of the embankment and deposit can produce long run-out and widespread downstream impact when pore pressure and beach management are not controlled.
• A tailings dam failure triggered by concentrated seepage and internal erosion showed how undetected piping can breach an embankment, and how freeboard and seepage monitoring are critical.
• A failure following extreme rainfall highlighted the role of freeboard, decant management, and event-driven monitoring during storms.
• A seismically triggered liquefaction underscored the need to characterize liquefiable layers and monitor post-earthquake pore pressure.

(These are described in general terms; the official investigation reports for each event contain the authoritative technical record.)

14.3 What good look like

Facilities that perform well over decades share habits: competent routine inspection, instruments tied to documented failure modes, validated and archived data, predefined action levels, independent review, and a culture where raising a concern is rewarded, not penalized.

14.4 Applying the lessons

For your facility, revisit Chapter 4: are the instruments tied to the real failure modes, are action levels predefined, and would an accelerating signal be detected and acted upon in time? The case histories answer "why this matters" — the rest of this reference answers "how."

14.5 Key takeaways

• Liquefaction of loose saturated tailings dominates catastrophic failures.
• Early signals are common but must be detected, communicated, and acted upon.
• Visual and instrumental surveillance are both necessary.
• Predefined action levels and a speaking-up culture save lives.