A truck driver working at the bottom of Australia's deepest gold mine gets loaded up with about 55 tonnes of precious cargo — hard rock blasted from the Earth and containing small specks of the yellow metal.



Key points: Gwalia is the deepest trucking mine in the world and can trace its history back to the 1890s

Gwalia is the deepest trucking mine in the world and can trace its history back to the 1890s Today, mining at Gwalia has reached a depth of 1,660 metres below the surface and the plan is to reach 2,300 metres by 2031

Today, mining at Gwalia has reached a depth of 1,660 metres below the surface and the plan is to reach 2,300 metres by 2031 The mine's name can be traced back to its Welsh heritage with former owners, Sons of Gwalia, translating to Sons of Wales

For every tonne trucks cart to the surface there might be only seven grams of gold, the equivalent of about one teaspoon.



Driving at the speed limit of 30 kilometres an hour, it takes drivers just under two hours to make their way to the surface to dump their load and head back down.



This is Gwalia in Western Australia's remote northern Goldfields.

Today, it is the deepest trucking mine in the world and can trace its history back to the 1890s when former US president Herbert Hoover was mine manager.



The mine's rich yet bloody history includes the deaths of 83 miners between 1898 and 1995 when 24-year-old diamond driller Graham Martin died on the job.

A truck on its way back to the surface. ( ABC Goldfields-Esperance: Jarrod Lucas )

Since its discovery in 1896, Gwalia has produced more than 5.5 million ounces — worth about $10 billion at today's gold price — to make it one of the richest gold mines in Australia's history.



The mine's name can be traced back to its Welsh heritage with former owners, Sons of Gwalia, translating to Sons of Wales.



Sons of Gwalia is now known for one of the biggest corporate collapses in Australian history, with its 2004 demise marked by debts of more than $800 million.



A truck driving down the ramp at the Gwalia gold mine at sunset. ( ABC Goldfields-Esperance: Jarrod Lucas )

Since Melbourne-based St Barbara took over ownership and restarted mining in 2008, there have been gold price crashes, skills shortages and a once-in-a-generation mining boom.



But it has been a defining decade in Gwalia's history, during which the mine has produced more than two million ounces of gold.

Jumbo operator Jean Dre Boshoff installing ground support more than one kilometre below the surface. ( ABC Goldfields-Esperance: Jarrod Lucas )

Modern miners reaching new depths

Today, mining at Gwalia has reached a depth of 1,660 metres below the surface and the plan is to reach 2,300 metres by 2031.



Gwalia employs 170 St Barbara workers, mostly on the processing plant, and 430 contractors who take care of mining.



Modern mining techniques have replaced the original wooden headframe and shaft, which was saved and now forms part of a museum alongside the old mine manager's accommodation, known as Hoover House.



The underground portal which was blasted into the bottom of a giant open pit also bears the name of the 31st President of the United States.



The mine was originally established in 1897 by Herbert Hoover, who later became the 31st President of the United States. ( ABC Goldfields-Esperance: Jarrod Lucas )

Truck drivers wind their way up the Hoover Decline — a rocky road spiralling through the Earth which is nearly 12 kilometres long.



In a 12-hour shift, truck drivers typically manage about four return trips from underground to the surface.



Temperatures at the bottom of the mine are close to 30 degrees Celsius, the humidity levels are on par with Australia's hottest tropical destinations and long shifts make it a tough slog for miners.



An underground loader, known as a bogger. ( ABC Goldfields-Esperance: Jarrod Lucas )

New ventilation to improve conditions for workers



One of the biggest challenges to extend the mine life at Gwalia is to get chilled air from the surface to the miners working below.



That is why $80 million is being spent to improve the mine's ventilation, including sinking large new shafts to reach the deepest parts of the mine.

St Barbara managing director Bob Vassie is upbeat about the future prospects at the Gwalia gold mine. ( ABC Goldfields-Esperance: Jarrod Lucas )

St Barbara managing director Bob Vassie said there was no end in sight for Gwalia.



"This mine made over $250 million last year, so if you're that strong you want to be doing it for longer," he said.



"Our previous mine life was only to 2024, and we've been able to extend it out to 2031, but the only way we can do it is by adding more ventilation.



"We'll probably have to put in more ventilation in future years just to keep going deeper and deeper because we haven't found the end of this ore body yet.



"We're already looking at going down to 2,300 metres below surface, so we're setting ourselves up for a long future here."

Miners install additional ground support at Gwalia. ( ABC Goldfields-Esperance: Jarrod Lucas )



Waste rock to stabilise old mine workings



The deeper mine plan will see the truck fleet expanded from nine to 15 over the next three years, creating more diesel emissions which makes air quality another consideration.



Another challenge at Gwalia is the amount of waste rock being carted to the surface.



About one in five trucks carries waste rock, but soon that problem will be solved because of an innovative feat of engineering.



St Barbara managing director Bob Vassie (right) inspects construction works underground. ( ABC Goldfields-Esperance: Jarrod Lucas )

At 1,420 metres below the surface, a $20 million project to crush waste rock, mix it with cement and backfill into old workings is nearing completion.



It has taken more than 12 months to install the paste aggregate fill plant, which included carving out huge underground caverns to house the equipment.



"If we can crush it and mix it underground, that keeps the mine stable by filling up the old workings and saves us having to truck it to the surface," Mr Vassie said.



Most gold bars poured at Gwalia are worth about $1 million. ( ABC Goldfields-Esperance: Jarrod Lucas )

"There are geotechnical challenges with mining at depth, but we're fortunate that our rocks are quite yielding and forgiving.



"As long as we mine to a very set sequence and we don't get out of step, we don't create too many geotechnical or rock condition issues, unlike our neighbours in Kalgoorlie who have to watch that a lot harder.



"It does get hot the deeper you get and the humidity from ground water means it can get pretty intolerable, so it's really about adding ventilation and mining in a certain sequence that keeps everything safe."



Gold room supervisor Henrik Rasmussen stamps a gold bar, worth about $850,000 at today's gold prices. ( ABC Goldfields-Esperance: Jarrod Lucas )

Precious metal kept under high security



The ABC was given rare access to film a gold pour at Gwalia.



Each gold bar is weighed and stamped before being shipped off to the Perth Mint. ( ABC Goldfields-Esperance: Jarrod Lucas )

The 14,113-gram bar produced was worth about $850,000 at today's prices — good enough to buy a house in Sydney or Melbourne.



Most gold bars at Gwalia are typically worth $1 million, with some of the highest purity gold in the country averaging around 92 per cent.



All the bars are shipped off to the Perth Mint for further refining.



The jaw-dropping value of the precious metal is underlined by the high levels of security at gold mines.

As one worker quipped, $10 million worth of iron ore from WA's Pilbara would take a bulk carrier a few weeks to sail to China, but $10 million of gold could fit easily in the boot of a standard car.



The furnace burns at close to 1,000 degrees Celsius. ( ABC Goldfields-Esperance: Jarrod Lucas )

Golden days at Gwalia far from over



The big question for Gwalia is whether mining can go beyond 2,300 metres?



The deepest mines in the world are in South Africa, where shafts are approaching depths of up to 5,000 metres.



Mr Vassie said safety was the biggest consideration in mining deeper.

Gwalia exploration manager Bob Love inspects drilling core samples from more than two kilometres below the surface. ( ABC Goldfields-Esperance: Jarrod Lucas )

"What happens after that [2,300m] is controlled by your mining rate and the design of your workings," he said.



"The deeper you get you don't try and open up too long a space before you fill it up, otherwise you run the risk of it collapsing.



"There's a lot of things we can do to potentially go deeper than 2,300m but it might create a change that might drop our mining rate, so they're the sort of things we have to balance.



"A future out to 2031, that's quite a long future in terms of Australian gold mining.



"We're also drilling what we call under the headframe, looking for old historic workings, so we're drilling to look for potential parallel mines where we can use the same infrastructure."



Tag boards are used to keep track of personnel working underground, as mine manager Andrew Walker tags on. ( ABC Goldfields-Esperance: Jarrod Lucas )

Fond memories from ghost town



The sudden closure of the mine in December 1963 turned Gwalia into a ghost town virtually overnight as the population fell from about 1,200 to just 40 people in three weeks.



Terry Demasson blew the final whistle at Gwalia and he kept it as a memento.



The 73-year-old was a teenager working as an apprentice fitter at the time.



Gwalia's original timber headframe was built in 1899 and used for hauling miners, horses and gold-bearing ore out of the underground mine. ( ABC Goldfields-Esperance: Jarrod Lucas )

"The first time I went underground I was bloody terrified," he said.



"I turned my light off on my helmet — we had electric lights by then — and you've never seen anything so black.



"And I mean black, there was nothing, so I turned that [light] on pretty quick I can assure you.



"Somehow I found where I was going."



Mr Demasson remembers how the old miners used timber for ground support, instead of the steel used today.



"For every tonne of ore that came out, there was a tonne of timber that went into the mine to hold it up," he said.



Feral goats regularly skirt the edges of the Gwalia open pit. ( ABC Goldfields-Esperance: Jarrod Lucas )

Horses worth their weight in gold



Mr Demasson recalled how horses were used underground until 1958 to push rail carts full of gold-bearing ore.



They were kept underground constantly, until they were eventually replaced by motorised carts.



As a child, Mr Demasson can remember the horses being brought back to the surface.



"They brought them all out and stabled them in a paddock and put bags on their head, so they could slowly introduce them back to the light," he said.



"They couldn't see because they were in darkness all the time.



"That was pretty amazing. I saw them come out — I was only a kid then."

Terry Demasson stands outside of an abandoned house in Gwalia. ( Supplied: Kate Ferguson )

The old-time miners made it about a kilometre below the surface using hand-held tools and eventually hand-held mechanised drills, known as air-legs for their use of compressed air.



In the late 1990s, Mr Demasson went back underground at Gwalia for the first time since it closed.



"It was exactly the same as we'd left it 35 years before," he said.



"The tools were still hanging on the board and you could still smell the grease. It was like we'd walked out the day before."



A miner during the early days of the Gwalia gold mine. ( Supplied: Gwalia Museum )

Mr Demasson said he was excited Gwalia was heading for new depths.



"They're still chasing the same body of ore that they were 100 years ago — it's unbelievable," he said.



"You think about the price of gold in our day and it was nothing in comparison to what it is today and the amount of dirt that they shift compared to what we did is huge.



"They're using trucks and we were using small carts."