SOMBA K'E/YELLOWKNIFE - Last Thursday, Roy Erasmus Jr. was one of 20 visitors walking approximately 240 metres below surface at the Diavik Diamond Mine, the temperature a balmy 4C.

From left, Yellowknives Dene First Nation chiefs Ted Tsetta (Ndilo) and Ed Sangris (Dettah) cut the ribbon in front of the portal leading underground at the Diavik Diamond Mine on Thursday. The day marked the official launch of underground mining at Diavik, after $800 million in investments by co-owners Rio Tinto and Harry Winston Diamond - Guy Quenneville/NNSL photo

Scanning the dark wet tunnels measuring 5.6 metres high and 5.3 metres wide with a headlamp affixed to his helmet, the president of Deton' Cho Corporation remarked, "I feel like I'm in the beginning of a Bruce Willis movie."

Over the last two-and-a-half years, Rio Tinto and Harry Winston Diamond Corporation, co-owners of Diavik spent a combined $800 million on the development of Diavik's underground mine, which officially began production last week.

The launch was marked by an on-site ceremony attended by a mix of mine site workers, Yellowknife Diavik staff watching via live teleconference, and visiting dignitaries.

With that now behind them, Diavik's owners and operator, Diavik Diamond Mines Inc. (DDMI), enter a challenging phase in the life of the mine, still predicted to extend beyond 2020.

"Going underground is expensive for a whole range of reasons," said Harry Kenyon-Slaney, chief executive of Rio Tinto's diamonds and minerals division.

"A new fleet of smaller equipment is required to transport mine material - 50 tonne haul trucks as opposed to 250 tonne haul trucks currently in use on surface. Air needs to be heated underground, and every tonne of soft kimberlite ore extracted needs to be replaced with cemented paste - backfill."

In addition, 20 kilometres of underground tunnels were constructed.

"In more local terms, that's the distance between downtown Yellowknife and the Prosperous Lake boat launch on the Ingraham Trail," said Peter Vician, deputy minister of Industry, Tourism and Investment.

The tunnels required other underground facilities: rescue bays, washrooms, ventilation systems, repair shops, raises (vertical tunnels) for ventilation and water removal, and storage areas.

New infrastructure was required on the surface, too, including the new crusher and paste backfill plant. The mine also had to double its water treatment plant capacity, and add accommodations and a mine dry building which includes change rooms.

Among the more innovative pieces equipment now being used at Diavik are automated scoop trams - heavy mobile equipment used to move ore and rock in the tunnels underground - that can be remote operated from the comfort of the office.

"This system takes the operator out of the underground environment and into a much safer office workplace," said Kenyon-Slaney.

But as attendees were reminded by Bob Gannicott, chairman and chief executive officer of Harry Winston, the large investment only serves to remind people that as Diavik prepares to enter the second half of its life, keeping the mine profitable will become more challenging.

"We've already had the T-bone steaks and we've already had the prime rib roasts ... We now have to move on to the hamburger ... It's still nutritious stuff, but it requires more work," said Gannicott of underground mining.

"Nonetheless, it's our obligation to get every bit of it because when we leave here, no one's going to come back to get a second going. We have to take it all while we're here."

Diavik accounts for approximately 15 per cent of the territory's GDP, according to Kenyon-Slaney.

In 2012, open-pit mining will cease, at which point Diavik will become a fully underground mine.

Between now and then, the mine's workforce, which averaged 810 direct employees in 2009, will hit a peak of around 1,200 before going back down to between 800 and 900 for the remainder of its life, said Kim Truter, president and chief operating officer of DDMI.

Diavik has produced 50 million carats since opening in 2003 - 5.6 million in 2009 alone. Reserves were estimated in 2008 at 62 million carats.

For more photos of the launching ceremony, see Wednesday's Yellowknifer.