The Pike River disaster is having a massive impact on mining work for Auckland's City Rail Link below the restaurants, karaoke bars and gay clubs on Karangahape Rd.
Deep beneath the K Rd ridgeline, workers are excavating caverns under strict mining regulations drawn up after the Royal Commission into the explosion that claimed the lives of 29 men in 2010.
Plant operators, mining specialists, electricians, plumbers and safety staff work underground, but before they can hang their name tag on a board and enter the mine shaft they must complete a safety competency course and a further tunnel induction course.
The two-day induction course includes how to put on an emergency breathing device in a dark, smoke-filled environment, how to fight fires and learning about the different gases lurking underground.
Strict rules apply to beards and moustaches to ensure the safe use of breathing devices in the event of an emergency.
And when underground, workers wear full PPE (personal protective equipment) that includes steel-capped boots, high-vis vests, safety pants, ear and eye protection and rescue breathing equipment.
As the tunnelling superintendent, Tomo Otene is responsible for the safety of the underground workforce, who work 12-hour shifts in groups of 12, and oversees heavy machinery that excavates the rock and is removing 100,000 tonnes of spoil.
His biggest safety job is assessing the risk of the ground strata and ensuring it is supported in a way that will not collapse.
Having worked on several large underground projects in Australia for more than 10 years, Otene is also acutely aware of silicosis, a deadly lung disease caused by inhaling silica dust.
"Over the last 10 years, a few mates of mine have been diagnosed with silicosis. I try and push the safety on to the guys here and let them know the reality of it," he said.
Otene, aged 50, returned to New Zealand one week before the first Covid-19 lockdown in March last year. He was drawn home to be near his and his wife's parents and Ngāpuhi connections in Northland.
He also rounded up about 80 per cent of the underground workforce in Australia to work on the $4.4 billion City Rail Link, a 3.4km tunnel linking Britomart to a new station at Mt Eden.
"It's good to be part of another big milestone. This would be the biggest public-realm project in New Zealand," said Otene.
City Rail Link Ltd chief executive Dr Sean Sweeney says underground staff will make light of the work, but there is an intrinsic danger.
"It's a bit like swimming in the water and you get spooked about sharks. You know the chances are low but you are confronted with the size and scale of it."
The environment underground, he said, is "pretty in your face". There's a constant roar from the ventilation units, it's hot and humid and on the day the Herald visited, there was a waft of diesel fumes.
Since the excavation work for the tunnels, platforms and cross tunnels began a year ago, there have been a few minor injuries, like cut fingers and one worker smashing himself in the chest with a hose for spraying on concrete, but no serious injuries below ground at the Karangahape station.
So far, the first of two caverns for the 203m-long platforms have been mined 32m underground for the Karangahape station, which will have two entry and exit points alongside the historic Mercury Theatre and Beresford Square on the other side of K Rd.
On May 17, the 130m-long tunnel boring machine, named Dame Whina Cooper, began its journey from the Mt Eden end to the Karangahape station, where because of the larger size of the cavern it will have to be dragged through to begin drilling the next leg to the Aotea Station in the central city.
The tunnel-boring machine started with a 40cm cut on the first night and is taking small steps until later next month when it will be in full production, travelling 32m a day, under the city.
Running the show underground are two excavating machines, known as roadheaders, with rotating cutting heads made of titanium grinding through hard basalt and softer east-coast bays sandstone.
In keeping with the mining tradition of naming large machinery after a woman, the larger of the two roadheaders is called Dame Valerie Adams and the smaller one is called Jean Batten.
At every step, 3m to 6m bolts are drilled into the rock and filled with grout to provide extra strength and shotcrete - spraying concrete - is applied over the top before the roadheader continues to the next section.
Specially adapted trucks remove the spoil to the mine shaft where it is lifted out on a 34-tonne bucket to an insulated noise enclosure building and loaded on to trucks to be used as construction fill on projects around the city.
Work has also begun on the floors for the station structures at Mercury Lane and Beresford Square before bottom-up construction begins next year, followed by the station fit-outs through to 2024.
Once completed, Karangahape station will cater for up to 9000 passengers an hour with public spaces at both entrances.
Aotea, the other new station located between Victoria and Wellesley Sts, 15m below Albert St, is being built by a cut and cover method. It is not as technically challenging as Karangahape, but is causing years of disruption to people, businesses and transport in the central city.
A new above-ground station is also being built at Mt Eden to connect to the western line and complete a city loop via Britomart.
When it opens in 2024, all going to plan, the CRL will be able to carry up to 54,000 commuters an hour to and from the central city - twice the current capacity of the rail network.
The main tunnel project is being built by the Link Alliance of seven companies, whose project director is Frenchman Francois Duboit. The project is a joint venture between the Government and Auckland Council.
The City Rail Link by numbers
3.4 - length in km of the route from Britomart to Mt Eden station
4.4 billion - cost of CRL shared between the Government and Auckland Council
2016 - start date
2024 - planned completion date
54,000 - maximum number of passengers who will use the new stations
1600 - number of workers at peak of construction
32 - deepest stop in metres on the line at Karangahape station