A dozen people were placed at risk at the Ettamogah site run by Burgess Earthmoving on April 10, 2018.

A rock blast involving 20 tonnes of explosives was conducted by Hamiltons Blasting Services, which sent rocks flying through the air.

Vehicles were hit and people narrowly missed as they ducked for cover.

A grey Volkswagen Amarok was hit with enough force to knock its bonnet off.

A red Nissan Patrol, white Nissan Navara and an excavator were damaged.

One rock flew within several inches of a worker's head and hit the excavator with enough force, it damaged a hydraulic pipe.

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The worker, who shouted "incoming" as rocks flew through the air, was diagnosed with PTSD.

Those at the scene had been standing too close to the blast site.

One man had remarked "we're not meant to be here" in the lead-up to the incident.

"Rocks have hit that hill beside us [on a previous blast]," he told others.

Burgess Earthmoving, which has been run by Russell Burgess for more than 35 years, was fined and ordered to pay costs of $235,000 in the District Court.

The company had admitted to workplace safety charges before Judge David Russell.

The court heard five members of the public, who shouldn't have even been at the quarry, were near the blast site without protective equipment.

"The likelihood of the risk occurring was significant," Judge Russell said.

"The potential consequences of the risk were death or serious injury.

"Simple and well-known steps were readily available to eliminate or minimise the risk.

"Indeed had Burgess followed its own safety system for blasting, most of the workers and other people put at risk would have been well outside the quarry.

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"Instead they were permitted by Burgess to stand in harm's way treating the blast as some sort of entertainment."

The judge noted that while Hamiltons was the specialist blasting company, the owner and operator of the quarry had its own responsibilities.

"Only through good luck most spectators at the blast were uninjured," he said.

"Burgess did have a documented safety system in place.

"That was of little use when personnel were not trained, supervised or even suitably qualified."

The court heard changes have been made at the site.

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