Lightning Threat Management and Continuous Improvement (?)

The recent revision of the AS1768:2021 'Lightning Protection' standard includes a new Appendix M 'Lightning Risk in Mines' which outlines some detailed guidance by which higher-risk operations can now review their existing Lightning Management Plans and apply 'continuous improvement', that demonstrates some intention to ensuring best practice is leveled against what is a common, known, and dare we say misunderstood fatal risk.

The mining and resources sector must always be considered higher risk, due to a large workforce where a large percentage will primarily work outdoors, and who may regularly be exposed to periods of higher risk thunderstorm conditions, sometimes on a daily basis, and especially during the summer months.

Additionally, if we consider where our key mining and resource areas are located, it can be shown that our major resource areas are well concentrated across geographic regions that exhibit risk profiles that are significantly higher than what might be considered 'the average'.

So what would be considered as being 'average', and what would constitute an operation being considered as 'higher risk' ?

There are two (2) key primary metrics that will determine any greater exposure to high-risk conditions.

These are:

• Annual thunder-days (Td) = total days where lightning is seen, or thunder heard.
• Ground flash density (Ng) = the number of Cloud to Ground (C-G) strikes per km2.

Where a higher than average lightning risk might be considered wherever;

• Td = / > 15
• Ng = / > 2

As can be shown on the Ground Flash Density (Ng) Map (Figure 1), many of Australia's major resources areas are situated in regions with an Ng that exceeds >3.

     Fig 1: Average Annual Ground Flash Density Map-Courtesy Bureau of Meteorology         

Additionally, the Annual Thunderday (Td) map (Figure 2), shows many of Australia's major resources areas are situated across regions where Td exceeds >25.

 
       Fig 2: Average Annual Thunderday Map-Courtesy Bureau of Meteorology         

The mining and resource sector can also demonstrate having a very high (some might say disproportionate) number of significant lightning incidents that have affected the sector in recent years, which has included several fatalities, many serious injuries, and numerous other significant miss and other high potential events.

What should set the alarm bells ringing is that these injuries/ fatalities/incidents have continued, despite an army of dedicated health and safety professionals, armed with an arsenal of risk mitigation controls which include:

• Lightning Management Plans (LMP)
• Lightning Risk Assessments (LRA)
• Safe Working Procedures (SWP)
• Trigger Action Response Procedures (TARP)
• Lightning Threat Detection and Notifications

Yet despite all the professional human resource, and all of these controls;

1. How is it that the mining/resources sector is so prone to so many ongoing and negative lightning interactions?
2. How is it that the human statistics have continued to fall through gaps, despite all the human resources, threat detection technology, and documentary controls?

There are many factors that are too detailed to include within this post, and which will be expanded on in future posts, but it is our 'informed' view that the single biggest contributory factor is the general publics 'ill informed' understanding of what lightning actually is, and how it injures.

Too often our own ‘common sense’ thoughts and extrapolations of our own electrical experience, will cloud any informed understanding of the lightning hazard and its various risks, which will more often than not will be 100% wrong about the actual mechanisms that will be in play during any significant lightning event.

And whilst it may be assumed that lightning follows the technical rules of physics and electricity, the reality is very different, where the the physics and the behavior of lightning, are completely different to 'manufactured' electricity.

Lightning is a higher frequency (DC - kHz) current source involving potentially 100's of thousand of amps, whereas mains power is a low frequency (50/60 Hz) current source, to which a normal household power outlet will connect equipment up to maximum of 10 amps.

Lightning is fundamentally different in every respect!

Subsequently, those health and safety professionals who are tasked to identify, assess, document, and develop the administrative controls that supposedly deal with this hazard, do so without any sufficient understanding as to the reality of the technical nuance, or the various 'direct' and 'indirect' injury mechanisms that are involved.

The reality is that 95-97% of all significant incidents that have resulted in injury and/ or fatality on mining and resource operations, will have been attributed to 'indirect' lightning injury mechanisms, that most people will not even be aware of.

For those readers who may now be wondering, we can advise there are seven (7) common 'indirect' lightning injury mechanisms which can potentially impact any typical mining and resources operation during any thunderstorm, and which make up this 95-97% of all lightning injury/ fatality statistics.

So, how many of these 'indirect' lightning injury mechanisms are YOU (the reader of this post) familiar with?

Lets now take it up a level!

Now go and ask your own 'Health and Safety" department this same question, and then consider whether existing administrative controls cater to any 'indirect' injury mechanism.

And there it is!

Grant Kirkby- Lightningman