Twin shafts double the challenge at Appin as Redpath and GM3 dig deep into safety innovation and lessons every mining professional should know

It’s not every day you hear about two massive shafts being sunk side by side in Australian coal country, each with its own design, equipment, and risks. But that’s exactly what’s happening south of Sydney, where GM3 and Redpath are tackling one of the most complex ventilation projects in the nation’s underground mining sector.

At the Mechanical Engineering Safety Seminar (MESS 2025) in Sydney, Quinton Wilkinson, project manager at GM3, and Nigel Bennett, engineering manager at Redpath, gave a candid account of progress and pitfalls on the Ventilation Shaft 7 & 8 Project for the Appin Mine. Their talk blended technical detail, hard-won lessons, and the occasional dry joke — but at its heart was a story of risk, resilience, and learning in real time.

Why two shafts, and why now?

The Appin complex, owned by GM3, brings together the legacy of multiple underground coal mines — Appin West, Appin, and West Cliff. After decades of longwall mining, the resource base is shifting north-west, far from existing infrastructure. Ventilation was becoming the bottleneck.

“The future mining domain is a long way from any of our intake or upcast shafts,” Quinton explained. “Yes, we’ve got booster fans, but they’re not enough. We needed new ventilation capacity if we wanted to keep the mine viable.”

The solution was bold: construct two new shafts, along with a switchyard, three main fans, and four service boreholes. That meant not only digging deep into sandstone and coal, but also building the surface infrastructure to power and support the mine’s longwalls.

From paddock to headframes

Quinton walked the audience through the site’s transformation. “Four years ago, it was just a paddock,” he said. “We had to relocate high-voltage services, upgrade the road intersection, and even deal with a dam that sat right over where Shaft 7 would be — a nice touch for anyone who likes water ingress.”

Within a year, civil works were complete and headframes started to rise. By 2024, Shaft 7 was commissioned and work had begun on Shaft 8. Today, one shaft is in main sink and the other is following close behind, supported by a switchyard commissioned in March that now powers the Appin longwall. The boreholes, drilled by Silver City, came in ahead of schedule, providing feeders, monitoring capacity, and compressed air.

On paper, progress looks linear. In practice, it’s been anything but.

Sharing control: safety management at scale

One of the most striking elements of the project is its safety governance. GM3 is the mine operator, but it doesn’t pretend to be a shaft sinking specialist. That expertise sits with Redpath.

“GM3 can’t just hand over our obligations as mine operator,” Quinton stressed. “But it makes sense for Redpath, with their skills and experience, to have management and control of the site as principal contractor. Our role is oversight — verifying they’re complying with their own safety management system.”

That oversight is far from passive. It includes in-field verifications with crews, monthly “deep dives” into principal hazards like explosives or mechanical controls, and reviewing control measures against legislation and practice. Nigel acknowledged the value: “It’s like third-party verification of our systems. They find issues, yes, but it’s a good thing. It makes us sharper.”

The engineering jigsaw

For Nigel, who’s been on the project for more than three years, the real story lies in the engineering.

“Every design choice cascades,” he explained. “Stage design dictates stage weights. That drives rope selection. Rope selection defines headframe loads. Winder capacity ties into all of that. And the kicker? The first thing you need in the ground is the shaft collars — but that’s the last thing you can actually design. Everything is interconnected.”

The regulatory environment added layers of complexity. Every winder and stage had to go through design registration, calculations, and commissioning before use. “We had good intentions early — even met with the regulator back in 2022,” Nigel recalled. “But carrying through final calculations that meet verification standards is another story. It’s a steep learning curve.”

New tools, old problems

The shafts are being sunk using conventional drill-and-blast methods, but the equipment has a twist. Air-powered muckers, rarely seen in Australia, were chosen to minimise ignition risks in a coal environment. Jumbos had to be reverse-engineered because no air-powered models were commercially available.

“The fitters are used to modern rigs with diagnostics and touchscreens,” Nigel said. “These have no electrics — just hoses everywhere. It looks complicated, but it’s brutally simple. The challenge is teaching people to troubleshoot without relying on electronics.”

Operator training has been a constant challenge. Shaft sinking isn’t like development mining — operators must multitask across jumbos, mucking, and shaft stage work. “In a normal mine, someone might spend five years underground before they touch a jumbo,” Nigel noted. “Here, they might be on it two or three times a week, sharing responsibilities across multiple people. It’s a different world.”

Misfires, mud, and management of change

Technical issues compounded the learning curve. Water ingress from the dam above Shaft 7 produced a steady inflow of 1.5 litres per second, turning blasted sandstone into “soupy mud” that was hard to muck and transport. Misdiagnosed gearbox problems led to unnecessary replacements. Misfires plagued blasting, traced back to electronic detonators being crushed by overpressure.

Perhaps the most sobering incident came in May 2025. A modification intended to improve access created an entanglement risk. A worker narrowly avoided serious injury. “That was a real soul-searching moment,” Nigel admitted. “We had to overhaul our entire management of change process. It forced us to confront how easy it is for small adjustments to introduce fatal risks.”

People, psychology, and pitfalls

Beyond engineering, the project exposed human factors. Quinton and Nigel referenced the Peter Principle and the Dunning-Kruger effect — promoting people too fast, or overestimating competence after partial learning. Both can have safety consequences.

“You don’t know what you don’t know,” Nigel reflected. “A little knowledge can be dangerous. And if you promote someone beyond their competence, you set them up for failure. We’ve had to build retraining and simplified safe work instructions into everything we do.”

Signs of success

Despite setbacks, there are wins. The team has brought water under control with pumps and rings, shifted from benching to full-face sinking to cut 20 steps from the cycle, and refined blasting designs to reduce detonator failures. At Shaft 8 they’re more than 170 metres down, while Shaft 7 is past 80 metres. The fans under construction will deliver 15 megawatts of ventilation power — essential for the future of Appin.

“We like to think we’re on the road to success,” Nigel said. “It hasn’t been easy, but we’re now sinking steadily, learning as we go.”

Why this matters for mining professionals

For practitioners across mining, this project isn’t just about two shafts in New South Wales. It’s a case study in modern shaft sinking:

• How to allocate safety responsibilities between operators and contractors

• How to manage interdependent engineering systems under tight regulation

• How to train and support crews in rare, high-risk tasks

• How to adapt when new equipment doesn’t behave as expected

Most of all, it’s about acknowledging mistakes and building resilience. “We’re not coming off the back of ten of these projects in Australia,” Nigel pointed out. “We’re learning, often the hard way. But those lessons are valuable for anyone in mining who’s thinking about complex infrastructure.”