Identifying environmental risks is a fascinating task. However, finding a risk is not enough; it must be assessed correctly. Here is an interesting example where logic failed.
Given:
The Group's Decision:
What was the group's logic?
Large-scale blasting occurs weekly. Every blast produces rock fragments.
The probability of the risk occurring is maximum — seems logical.
If the fuel storage sustains mechanical damage, all the fuel will spill. The impact is the maximum possible — an environmental disaster — which also seems logical.
So, did the group assess the risk correctly?
Let's try to break it down.
In risk assessment, it is standard practice to correlate the probability of an event with the consequences of that specific event. What the group did was correlate the probability of a fairly frequent event (a flying fragment) with the most severe consequences of a different event (a total diesel fuel spill). I think it is clear to everyone that the probability of Event 1 (a rock fragment flying out) and Event 2 (a large rock fragment flying out, hitting the storage facility, and destroying it) are vastly different.
When the group was asked: "What is the probability of Event 2 (a large rock fragment flying out, hitting the storage facility, and destroying it)?"
"Hypothetically possible, but the probability is extremely low," the group answered unanimously.
We've sorted out the probability, but what about the consequences?
There is something to discuss here as well. Existing safeguards are very often forgotten during risk assessment. In our case, the concrete bunding of the storage facility is designed to contain any spilled fuel.
When the group was asked: "How much fuel could leak into the environment, taking existing safeguards into account?"
"It might not leak at all," the group replied.
The group was offered a choice: keep the initial maximum risk rating or reassess the risk. The group reassessed the risk, and it received a lower score.
What would you have done?