An aging dam containing mining tailings is threatening to break and disgorge contaminants into the Salmo River near Nelson as a double onslaught of heavy rainfall and melting snow has forced officials to declare a local state of emergency.

“The worst-case scenario would be that the dam would fail and you’d get downstream impact,” said Bill Macpherson of the regional district’s emergency operations centre. “There could be a discharge of contaminants into the Salmo River.”

This is unlikely because the weather forecast is favourable, he said, and it was the rising water levels that caused the dam, which holds mine tailings from an old lead-zinc mine, to begin to leak. The area got about 30 mm in four hours on Tuesday, he said.

Emergency workers are doing overtime to ensure the river won’t be contaminated.

The water flow from the pond is travelling at about four cubic meters a minute, Mr. Macpherson said.

Three pumps were already working to lower the pond’s water levels on Wednesday afternoon, he said. A larger, fourth pump was expected to arrive on Wednesday evening.

Geo-technicians were at the site all day, but the conditions up to Wednesday evening made it too difficult to place equipment safely to do any remediation work, he said. The technicians hope they will be able to put the equipment in place in the next 24 hours and begin to move rock and other material to stop the seepage.

Environmental monitoring is also under way, he said. The quality of the water coming thro ugh the pumps and seeping out is being checked for mineral levels. On Wednesday evening, there was little to no contamination, he said.

While only a rental property is in the vicinity, a highway runs below the site. So far, no private or public property has been damaged, but all residents have been warned of the local state of emergency, he said.

Other land instability issues are popping up across the district. Officials are monitoring road conditions, and debris threatened one bridge. Officials issued evacuation alerts to 32 residences in one area and recommended four be evacuated in another. One resident voluntarily complied with the suggestion.

The district is warning residents that the rain and snow melt have raised dams and reservoirs on the Columbia-Kootenay river system to nearly their maximum. Some areas of Kootenay Lake have reached 40-year high water levels, and the lake could rise slightly higher depending on the weather.

Photo: High water levels in lakes and waterways like the Salmo River put the Kootenay region under a flood warning.