Diavik says bulldozer ‘submerged’ at mine is probably gone for good

A bulldozer that sank into a mud-like material at the Diavik diamond mine probably can’t be retrieved and may stay there forever, the mine says.

On December 10 last year, the Caterpillar D10 bulldozer was lost while being operated via remote control.

The dozer had been working in the processed kimberlite containment facility, a lined dam built to permanently store waste rock from which diamonds have been extracted.

Diavik is working to cover this processed kimberlite with more rock, since some of it is a fine and unstable material described by the mine as “similar to the consistency of soft mud” that could be a threat to wildlife.

The dozer went into some of the mud-like material – and could not be retrieved.

“This physical stability risk was the reason that the equipment was remotely operated. No personnel were at risk and no one was injured in the incident,” a spokesperson for Diavik owner Rio Tinto said in a Monday statement to Cabin Radio.

“Recovery does not appear to be possible due to the risk to personnel and the nature of the unstable material,” the mine wrote in a January 9 letter published to a regulatory registry last week.

In an email to Cabin Radio, the Rio Tinto spokesperson said trying to get the dozer back did not appear to be “safe or practical.”

As a result, the piece of heavy equipment is likely to remain trapped there.

The company estimates about 1,260 litres of diesel fuel and oils were on board at the time.

A new D10 dozer can cost millions of dollars. Equipment trading website MarketBook states the average price for a used D10 is about $220,000.

Mining at Diavik, which is situated on Lac de Gras in the remote tundra northeast of Yellowknife, is expected to end in the next couple of months. At that point, the focus will switch to trying to safely close the mine.

The current plan is to leave the bulldozer buried within the processed kimberlite containment facility, known as the PKCF.

“The dozer is stable in the lined PKCF and will not alter long-term stability of the PKCF,” Rio Tinto’s spokesperson stated.

“As the PKCF has seepage interception wells and lined dams that are engineered to be impermeable, there is very limited potential for release to the environment.

“There are also downstream containment structures (impermeable ponds) and monitoring programs which effectively manage the risk of any release to Lac de Gras both in the short and long term.”

In a report filed with NWT government environmental inspectors, Rio Tinto said an extra berm had been placed near the scene of the incident with signage “to avoid further incidents in the area.”