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SOMBA K'E/YELLOWKNIFE
A rock slide in the Diavik diamond mine's open pit could have been much worse, if not for advanced warning technology.

Workers inside the open pit at the Diavik diamond mine, pictured above, had an advanced five-hour warning before a large rock slide sent 5,000 tonnes of debris toward the bottom on Aug. 4. - NNSL file photo

Only two employees were working on the rock bench near the bottom of the open pit the night of Aug. 4 when an alarm sounded for them to evacuate at about 10 p.m., said Corey McLachlan, acting manager, community and external relations.

"We had an alarm go off in our open pit indicating that there was some movement of rocks," he said.

The open pit portion of the mine is equipped with two separate safety systems, said McLachlan. The first alarm to sound is a radar system that constantly scans the pit walls, looking for any sort of rock movement.

About an hour after the evacuation, the secondary safety system, called a total optical survey, also sent out an alert that detected moving rocks.

The actual slide did not take place until about 3 a.m., said McLachlan, but when it came, it came with force.

Roughly 5,000 tonnes of rock broke free from the side of the pit and fell about 10 to 12 metres to the shelf the workers had previously been working on, near the bottom of the pit.

The amount of rocks that fell was significant and would classify as a fairly large rock slide, said McLachlan. However, because of the advanced warning, no people were endangered and no equipment was damaged during the event.

"It was an example of the reason you have these safety systems in place and how well they can work," he said.

The pit did not re-open until Aug. 21. As an added safety precaution, employees were only working in the pit during daylight hours as of press time.

In the interim, between the slide and the restarting of mining operations in the pit, workers knocked off all loose rocks from the sides of the pit, strung heavy-duty mesh coverings on the exposed rock and continued to monitor the area for any further movement before determining it was safe, said McLachlan.

Currently, the Diavik mine is transitioning from open pit to underground mining. Therefore, the pit is scheduled to be closed within the next month.

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