Blaster’s guide to lightning safety

I was recently on a consulting trip to an aggregate operation in the southern U.S.

After traveling 12-plus hours the day before, I was relieved when I woke up to a bright and sunny sky, as that was a sign that a blast would be fired that day. However, the sky turned dark shortly into my journey to the remote location.

When I pulled up to the site’s office, I asked the mine manager if the plan was still to fire the day’s blast that I was on-site to evaluate. The mine manager assured me they had enough time to get the shot loaded and fired before the storm rolled in.

We went to take a look at the pattern and the blaster’s loading with no storms immediately present. Afterward, we headed to the office to talk over the blast and what I would look for from a performance standpoint.

After about an hour, we walked outside to find the storm directly overhead. The plant had shut down due to lightning, and my phone’s lightning detector app showed lightning striking within a one-mile range.

I was disappointed that the blast would not fire and surprised that the crew did not clear the site and fire before the storm was overhead. That’s when we heard the 30-second blast warning: The crew had loaded and was about to fire the blast in the middle of a storm – with lightning directly overhead.

Lightning and explosives do not mix well together. Blasters are typically trained to understand that all blasting activities cease when a storm approaches. Many states ask questions about handling lightning in their blaster’s license testing. The Mine Safety & Health Administration also has specific regulations about lightning to prevent injuries and fatalities.

Yet, we know lapses in lightning safety happen, as is evident from a lightning fatality that occurred in August 2019.

First precaution

The first precaution a blast crew can take is modify the approach it takes to daily work. If lightning strikes a blast, the holes do not detonate as per the timing of the caps. It will be sporadic, with some holes going off and others not.

This leads to a mess of material that has live explosives, boosters and caps still in the muck pile. The best method of preventing this is to not allow it to occur.

All blasts should be loaded so that, at any time, the blaster can stop loading and fire at least part of the shot. This removes the explosive from the rock. This also means loading all holes in row one (the row closet to the face) – and moving backward.

If lightning comes within 20 miles on a trajectory toward the site, clear the blast area and fire whatever holes you have loaded.

Second precaution

The second precaution is that all sites must have a lightning detection system in place that every employee has access to.

Today, many sites are transitioning to employees getting notifications on their phones. This can work some of the time, but what if an employee is not checking their phone regularly or their phone dies? All sites must also have an active lightning detection system, which can be a siren, a muster point or, at minimum, a person going around to check on everyone and ensure they know what’s happening.

Do not wait until lightning is 10 miles out to inform your blast crew. Keep them updated at regular intervals as the lightning approaches. The best practice is to alert them at 50 miles, 25 miles, 15 miles and 10 miles. This gives them a realistic window to fire the shot.

Final precaution

The final precaution is that all operations must cease when lightning is within a 10-mile distance from the blast site.

Lightning has been known to unintentionally detonate explosives when striking as far away as seven miles. No initiation system stops lightning from causing unintentional detonation.

Furthermore, lightning has caused unintentional detonation of blasts underground. When lightning is too close, be sure to clear and guard the blast area. This should follow the exact same procedures as the clearing and guarding during a blast – including public road shutdowns, if they occur at your site.

Lightning continues to be one of the greatest risks that blasters face. Make sure lightning is respected and that procedures are in place to mitigate the risk it poses.

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Anthony J. Konya is the vice president at Precision Blasting Services, consulting around the world in rock blasting and vibration from blasting. He is also the founder and CEO of Academy Blasting, an explosive engineering education company, and the host of AcademyBlasting.TV podcast.