A scheduled dam inspection Tuesday gave the Regional District of Central Kootenay officials a lucky break when they happened to discover a damaged retaining wall seeping water from a mine tailings pond.
Undetected, it could have spilled toxins into the Salmo River.
"It was just part of a regular inspection that happens monthly," said Bill Macpherson of the regional district's emergency operations centre.
"They go and look at it, and make sure that it's as it should be."
These monthly checkups are voluntary on the part of the regional district, which owns the former HB Mine property and uses it for its central landfill area.
The district is only required to submit an HB dam site inspection report once a year, wrote Jake Jacobs, a Ministry of Energy and Mines spokesman, in an e-mail to The Globe and Mail. Additionally, water-quality test results must be sent to the Ministry of Environment every month, he wrote.
An independent geotechnician conducts the dam's more thorough annual inspection, Mr. Macpherson said, and an environmental technologist has been inspecting the site monthly since 2009 – while obtaining the required water samples.
If the retaining wall damage had not been detected and the rain continued for two or three more days, the problem could have been much worse, he said.
"You quite conceivably could have had complete failure of that structure," he said.
In 2010, a breached dam caused a mudslide in Oliver and devastated orchards, vineyards and some houses. In response, the government launched an investigation. The final report noted mine tailings dams, such as this one, were not monitored by the province's Dam Safety Program. The author recommended these dams should have licensing and standards approaches consistent with those of structures monitored by the Ministry of Environment.
All dams under B.C.'s dam safety program have an annual formal inspection. Additional site surveillance must occur at least four times a year, but may be more frequent depending on how dangerous the dam would be to the public if it failed.
The Ministry of Energy, Mines and Petroleum Resources is responsible for monitoring mine tailings dams through an agreement with the Ministry of Environment, according to the report. The amount of times the former HB dam must be monitored has not changed since the report was released, Mr. Jacobs wrote.
Emergency workers have been on site since the breach was discovered during the monthly inspection and are trying to rein in the damage, Mr. Macpherson said.
"They've had some good success with reducing the [water] pressure through pumping overnight," he said.
Four pumps are removing excess water from the pond and redirecting it through a drainage ditch and into the Salmo River, he said. The water is not contaminated since the tailings do not dissolve in water and sit at the bottom of the pond, he said.