ORE2_Tailings and ALARP
Jan 4th, 2023
A colleague recently engaged a discussion on ORE2_Tailings and ALARP.
He presented various refences on the subject then asked us to check if ORE2_Tailings™ complies with the various definitions. Indeed, we have published on ALARP in recent international conferences:
- Oboni C., Oboni, F., A Case Study on ALARP Optimization, Tailings 2022, Santiago Chile, May July, 2022 and
- Oboni F., Oboni C., Optimizing mitigation of tailings dams portfolios, Tailings and Mine Waste 2022, Denver, CO ,November, 2021 (video).
We are delighted to report we found full compliance with the references. Indeed there is nothing in those texts that goes against Riskope’s day-to-day practice and the use of ORE2_Tailings™ for tailings dams quantitative risk assessment.
The sections below:
- show the title of the publications,
- give their links for reference and finally
- deliver our comments.
We use italics to highlight texts coming from those references.
However, before looking at the references, we will summarize the ORE2_Tailingstm procedure.
How we apply ORE2_Tailings and look for ALARP mitigation
A dam system quantitative risk assessment includes a first phase during which we compile the knowledge base. This may include deficiencies that we immediately highlight.
The second phase consists in evaluating the probabilities of failure and their consequences. There are more than one probability because of the various conditions (drained, undrained, etc.) the dam system sees along its life. These probabilities are benchmarked with respect to the world-wide tailings dams behavior, thus allowing to “anchor” the results to reality.
If the dam does not pass the benchmarking, its risks are considered intolerable, or for whatever reason the owner decides to mitigate the dam, then we would engage a ALARP procedure. The ALARP procedure looks at various mitigative stages. We generally discuss these with the owner and the EoR. The EoR delivers the costs of each mitigative stage allowing the analysis to proceed.
At the end we produce the risk abatement vs. mitigative investment graph. The crossing of the two curves is the “minimum mitigative ALARP level” one should consider. Please review our papers if you want to learn more.
And now, let’s discuss the references!
Forecasts or fortune-telling: When are expert judgements of safety risk valid?
We totally agree with the authors. That’s why we spent twenty years calibrating ORE2_Tailings™. Thanks to that calibration the results are now quite positively anchored to reality. The use of appx. 40 KPIs (“well understood local causal mechanisms”, using the language of the paper) ensures we keep the “mistakes” as much as possible at bay and enhances repeatability.
How to determine what is reasonably practicable to meet a health and safety duty
“The WHS Act imposes a duty on a person to ensure health and safety that requires the person to eliminate risks to health and safety so far as is reasonably practicable, and if it is not reasonably practicable to do so, to minimise the risks so far as is reasonably practicable.” We are in full agreement. Indeed, what we published to date shows how one can evaluate and justify with quantities that reasonably practicable. We consider that beautiful words and “judgements” may not be enough anymore, in our societies.
Indeed, we cover exactly what the standard specifies. That is:
“In relation to a duty to ensure health and safety, ‘reasonably practicable’ means that which is, or was at a particular time, reasonable to do to ensure health and safety, taking into account and weighing up all relevant matters including:
(a) the likelihood of the hazard or the risk concerned occurring
(b) the degree of harm that might result from the hazard or the risk
(c) what the person concerned knows, or ought reasonably to know, about the hazard or risk, and about the ways of eliminating or minimising the risk
(d) the availability and suitability of ways to eliminate or minimise the risk
(e) after assessing the extent of the risk and the available ways of eliminating or minimising the risk, the cost associated with available ways of eliminating or minimising the risk, including whether the cost is grossly disproportionate to the risk.”
ALARP for engineers: a technical safety guide
This is very complete guide. However, we could spend weeks discussing numerous points. Indeed, the text seems unfortunately anchored in past “good practice”. Furthermore many points are rather impractical for structures such as tailings dams. Also, we will not delve into the details of some statements that are dogmatic. One should look at them with modern eyes. Let’s however note that the matrix at page 89 presents very common and unfortunate mistakes!
Legal context of what is reasonably practicable
“The question whether a measure is or is not reasonably practicable is one which requires no more than the making of a value judgment in the light of all the facts.
… to determine what is “reasonably practicable” it is necessary to balance the likelihood of the risk occurring against the cost, time and trouble necessary to avert that risk”. Yes, we agree with the author of this presentation which was part of TMW2022 short course we recently cited. We support the “value judgement” with numbers and offer a quantitative estimate of the minimum level of the “balance”. Thus, again, no problem here.
The other slides in the presentation go again toward our day-to-day practice. Furthermore, our actions support the statement “It would not generally be practicable to take measures to guard against a risk to safety that was not reasonably foreseeable”. Indeed, we benchmark the dams (and their mitigations) with respect to the world-wide portfolio. Furthermore we use the credibility threshold (10-6) as a lower bound to our analyses.
“As a legal risk management principle, reasonably practicable requires you to demonstrate that you had:
▹ proper systems to manage the relevant risk; and
▹ adequate supervision/assurance to understand if those processes are implemented and effective”. Again, we couldn’t agree more. With our QRA we evaluate if the adequacy of the systems to manage the relevant risks. To accomplish that we deliver a discussion on causality and controls, including supervision and assurance.
We hope this text has brought some clarity related to the procedure we apply for quantitative risk assessment and mitigation ALARP.
We are pleased to confirm that ORE2_Tailings™ ALARP approach stands the test of comparison with the various references we examined to date.