AuRico Gold will remove a portion of the 70,000 trees planted on a tailings dam after the province said the seedlings were a potential safety concern.

In a July 2, 2014 report, the province’s geotechnical engineer noted an American dam safety association stated in a 2002 report “trees and woody vegetation have no place on the embankment slopes of an earthen dam.”

Concerns included blow down of trees with large root balls, internal erosion pathways created by rotting roots and habitat created by burrowing animals, wrote Ministry of Energy and Mines geotechnical engineering manager George Warnock.

Warnock instructed AuRico to explain if any special design features had to be incorporated into the dam at the closed Kemess gold and copper mine (about 320 kilometres north of Prince George) to accommodate the trees, particularly in the crest of the dam.

“It was unusual enough for me to raise the question,” Warnock said in an interview Thursday.

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He said the company maybe got “overzealous” in planting trees, but added the company has provided a detailed response that satisfied him. That included removing 4,000 of the pine, spruce and willow trees at the crest of the dam.

The AuRico report (and those from six other mines in B.C.) was obtained by The Vancouver Sun through a request to the Ministry of Energy and Mines.

The reports provide the first look at the results of B.C.’s inspection system, which is under scrutiny following the failure of the tailings dam on Aug. 4 at Imperial Metals’ Mount Polley gold and copper mine.

Among the other concerns highlighted in the sample of the province’s geotechnical engineering inspections are a crack in one of the tailings dams at NewGold’s New Afton gold and copper mine near Kamloops, and an unusual increase in water level readings in a dam instrument at Taseko’s Gibraltar gold and copper mine north of Williams Lake.

Source: The Vancouver Sun - see full article