Mine’s leaky dam blamed on heavy rain

by Michael Mosher on July 10, 2012

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Heavy rainfall and a sinkhole contributed to the partial failure of an earthen dam in the Kootenay region, say local officials.

The dam on the site of an old Hudson’s Bay lead-zinc mine south of Salmo, B.C., is part of the retaining wall for the mine’s tailings pond.

Community officials declared a local state of emergency last week after the dam began to leak.

“The sinkhole in combination with heavy rains, caused the slough, the failure, and then the subsequent seepage,” said Bill Macpherson, a spokesman for the regional district.

Mr. Macpherson said officials found the sinkhole on the inside of the dam, near the centre of the structure, after draining down the pond.

The sinkhole was found about 1.8 metres below the normal high water mark, and regular inspections would not have revealed it because of its location and depth, said a statement from the district.

Mr. Macpherson said the leaks have now been stopped, and officials are building up the face of the dam with rock, earth and fill.

“The whole area’s drying up, so it’s certainly improved from what it was,” he said.

Meantime, in the community of Valemount, to the northeast, high water in a creek triggered an evacuation order.

The order covers residents of four homes and was issued after rushing water eroded the banks of Swift Creek.

Residents were urged to leave their homes immediately and register with village emergency officials.

All other evacuation orders issued in B.C. because of flooding last month have since been rescinded, although some evacuation alerts remain in place, particularly in the Shuswap region east of Kamloops, including Sicamous.

The worst of the flooding in the province occurred in Sicamous and at one time forced about 300 people from their homes.

Full article…here

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