Drier weather eases flood threat on crumbling B.C. mine tailings pond

Improving weather conditions are helping crews draining an old mine-tailings pond near Nelson and Salmo, B.C., whose earthen walls began crumbling beneath heavy rain, The Canadian Press reported Thursday.

The southern B.C. region has been hit by flash flooding and residents of Sicamous, where homes were damaged late last month, have been warned to brace for another possible food as it appeared Sicamous Creek was clogged with trees and debris.

[ Related: Flooding easing across B.C. as weather dries up, waters recede ]

But the potential for a flood of tailings-laced water from the defunct Hudson's Bay lead-zinc mine in the Kootenay region presents a different kind of threat.

The Central Kootenay Regional District declared a state of emergency on Wednesday when the pond's retaining wall showed signs it could be washed away.

But Bill Macpherson, a spokesman for the district's emergency operations centre, said Wednesday rumours the earthen dam could fail were exaggerated.

"That's obviously a worst-case scenario and that's not where it's at right now," he told The Canadian Press. "It's dependent on the weather and the weather is favourable."

Macpherson said the emergency declaration will stay in place for at least a week while officials decide how to deal with the fragile dam.

District chief administrator Jim Gustafson said earlier this week officials were concerned that "moisture" was coming out of the dam and that if there was a breach, water would flow down the hill and across Highway 3, a major artery through the Kootenays, CBC News reported.

[Related: Teams assess flood-ravaged structures as some residents remain displaced ]

Any country where mining or minerals processing takes place is dotted with tailings ponds, some of them attached to inactive operations. There have been major failures that send the waste, sometimes very toxic, flooding across the landscape.

One of the best known recent incidents in October 2010 saw 700,000 cubic metres of red toxic sludge laced with arsenic and mercury from an aluminum plant inundate villages in Hungary and flow into the Danube River.

Alberta's Pembina Institute notes there have been several tailings dam failures in Canada, including the 2004 incident that spilled 6,000 cubic metres of waste from a former mercury mine at Pinchi Lake, B.C., and a 2008 breach of a dam at a copper mine near Chapais, Que., which released an unknown amount of tailings.