Con Mine discharge gets green light
Owner doubts treated water will reach Great Slave Lake due to dry conditions in tailings ponds
Meagan Leonard
Northern News Services
Wednesday, August 26, 2015
SOMBA K'E/YELLOWKNIFE
Owners of defunct Con Mine are ready to release a flood of treated groundwater from underneath the mine into Great Slave Lake but are doubtful it will reach it this year as the tailings ponds leading to the lake have almost completely dried up.
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Until now only surface water has been discharged from the site every four years. With completion of a new water treatment plant in July, the once contaminated groundwater can now be released. The groundwater filling up the old underground mine chambers will need to be drained every four years to keep the mine from flooding.
Treated water from the mine site drains into a small channel and then flows through the Meg/Keg/Peg lake system before emptying into Great Slave Lake. However, much of the system has dried up due to limited precipitation this summer.
In a letter to Environment Canada, Con Mine owner Miramar Northern Mining Ltd. stated water levels in the Keg/Meg/Peg lake water system were much lower than previous years and as a result it will be impossible to take samples from the planned monitoring location.
Originally, the plan was to collect samples from the Meg Lake exposure area but testing will now be done at Keg Lake.
"As of July this year, Meg Lake appears to be completely dry. This appears to be a natural phenomenon as regional water levels are very low," wrote environment manager Dwight Grabke. "(Miramar) could attempt to sample Meg Lake in August 2015 once effluent discharge commences; it is anticipated, however, that dry water conditions will persist and no water will be present."
He said it is unlikely the water will leave the system and reach Great Slave Lake this year.
"Keg Lake has low water levels and substantial portions of its shoreline are dry. Peg Lake contains some water although it is not flowing into Jackfish Bay (Great Slave Lake)," he said.
"Thus, residual water and/or treated effluent from the Meg/Keg/Peg chain of lakes is not currently flowing into Great Slave Lake."
Environment Canada spokesperson Danny Kingsberry stated in an e-mail standards ensure the release will be safe regardless of water levels.
"Lower water levels limit the availability of the effluent to be diluted by the receiving water body," he said.
"That is the reason why the effluent standards are set to be as protective of the receiving water as technically achievable."
He said there is no limit on how much water the mine can release, only the percentage of toxic contents.
Yellowknifer couldn't determine by press time whether the water discharged from Con Mine is treated enough to be drinkable.
Previous studies found the ninespine stickleback developed larger organs, including larger gonads, during periods of discharge from the mine.
Kingsberry said he could not comment on whether this is still a concern.
"It is not possible to predict the results of the biological monitoring study beforehand," he said, adding information on the effect of effluent on fish, fish habitat and fish use will be collected.
Some are not so sure the release will be completely harmless.
Weledeh MLA Bob Bromley, whose background is in biology, told Yellowknifer current environmental monitoring methods should be updated to account for the effects of climate change.
"These things were set up under completely different conditions than what we face today," he said.
He said although the water is treated, with no receiving body to dilute the contents, nutrients could become a hazard to wildlife.
"The contaminants could end up stranded on the surface and available to wildlife which of course are going to forage on the exposed lake bottom," he said.
Zabey Nevitt, executive director of the Mackenzie Valley Land and Water Board, said the board takes low water levels into consideration when determining its criteria for discharge quality.
The board is responsible for issuing the water licence to the company, which in this case, it did.
"Overall low water levels may mean less dilution in the receiving environment," he said.
"However, (criteria) are set conservatively to be protective and take into account the range of possible water levels, including low water levels."
Nevitt said although it's not anticipated, if abnormal data was returned during an environmental effects study, criteria could be changed.
"If the board saw impacts that were not expected, then the option would be available to change (criteria) if necessary," he explained.
Beginning operation in 1938, Con Mine is the city's oldest gold producing site. Production concluded in 2003 and treatment of water from tailings ponds is expected to continue for up to 25 years.
