Solomon Islands gold mine contaminated water spill disaster

Solomon Islands gold mine contaminated water spill disaster

Apr 20th, 2016

The Solomon Islands gold mine contaminated water spill disaster constitutes a perfect case for discussing the concept of failure criteria. Failure criteria is the mirror image of the success criteria. Failures are the events that generate risks studied in risk assessments.

Tailings dams are built with the purpose (goal) of storing byproducts of mining operations, i.e. the tailings. Tailings consist of finely ground ore (the mineral) and process effluents generated by mechanical and chemical processes.  In fact, those processes goal is to extract the desired product from the ore. It is unfortunately impossible to reclaim all reusable and expended processing reagents and chemicals.

Thus the unrecoverable and uneconomic metals, minerals, chemicals, organics and process water are discharged, normally as slurry, to a final storage area. That area’s name is, for example, Tailings Management Facility (TMF) or Tailings Storage Facility (TSF).

weir of the Solomon Islands gold mine

Weir of the Solomon Islands Gold Ridge mine

In the case of Solomon Islands’ Gold Ridge dam arsenic, cyanide and maybe selenium and mercury are present in the tailings. Excess water accumulated behind the dam.

Solomon Islands gold mine contaminated water spill disaster

Gold Ridge dam lately overflowed uncontrollably after heavy rain last week. In 2014 and 2015 the catastrophic flooding brough by Tropical Cyclone ITA and a close call  raised alarm at various levels.

Eight-thousand people live downstream.

Tens of millions of litres of water containing arsenic cyanide and heavy metals escaped from the dam via its weir. That event altered the life of downstream residents. As a result, Health authorities in Solomon Islands have released a statement advising downstream communities not to use rivers for drinking, cooking and bathing.

A weir is a structure built across a water course or on top of a dam allowing water to flow steadily over its top. Weirs built on top (at the crest) of a dam are there to allow excess water accumulated behind the dam to run away. That is, of course, without damaging the dam by uncontrolled overtopping.

Definition of success or failure criteria

We can imagine what environmentalist are saying. The dam is not protecting the environment from the chemical contained by tailings dam, therefore the tailings dam has “failed” because of the weir.

For the dam engineer the weir and its associated spillway relieved the pressure and reduced the likelihood of a dam collapse. The system worked perfectly! For dam engineers a dam failure is what we saw at Samarco or Mount Polley. The weir functioning is a success.

Is it possible to reconcile the two views?

When performing a risk assessment we lay out the goal of the system, its success or failure criteria. This allows us to depict the risk landscape in a more nuanced and truthful way taking into account different views from different participants.

There is nothing worse than people thinking they understand each other when discussing a poorly defined problem!

In the Gold Ridge case what are the consequences for the different parties?

The goal of the risk assessor is to deliver to the stakeholders a metric. IN fact the metric should encompass both concerns and to facilitate a healthy discussion.

The present situation at the Gold Ridge Mine arises from the lack of communication. Additionally, the resulting misunderstanding on what what constitutes a failure added a layer of confusion.

Risk Assessments. A case against slioed culture

The environmental agency, various Ministries, the dam engineer, the downstream villagers all have a different views of what constitutes a “failure leading to a disaster”. Indeed, because they operate in a information siloed environment, their communication is bound to fail leading to crises.

Oftentimes we perform our Risk Assessments to reduce that communication vacuum and allow sensible and rational decision making.

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Category: Consequences, Crisis management, Risk analysis, Risk management

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