No impact to surrounding area expected after mine water spill at Giant Mine

Approximately 30,000 to 40,000 litres of arsenic-impacted mine water that spilled on Sept. 3 at Giant Mine in Yellowknife is currently being investigated according to a recent spill report. 

Chris MacInnis, the director of the Giant Mine Remediation Project, said in a statement no impacts to the surrounding area have been found or are anticipated.

"While this is a large volume, the spilled mine water infiltrated the gravel pad and is expected to return to the underground mine pool where it will eventually be treated as part of the remediation efforts," MacInnis stated.

Parsons Inc, the main construction management company for the site, shared the report with involved parties including the Mackenzie Valley Land and Water Board on Sept. 4. It stated the water spill was due to a malfunctioning valve used to release trapped air from a pump system.

"Although the potential impacts of the spill are still being assessed," no water pooling or run-off was found, according to MacInnis. He added that the project team is working with the federal land-use inspector to determine if there could be impacts to the gravel pit and ground underneath.

Mackenzie Valley Land and Water Board executive director Kathy Racher said as per protocol a more detailed report will be submitted to the board and inspector within 30 days. She said the report will go into detail on what caused the spill and how it'll be prevented in the future.

"In this case, there will also probably be some information on anything that might've been impacted in the environment and if they need to do follow up remediation or monitoring," she said.

The report said the deep well pump that transports underground mine water was scheduled to automatically begin running between 4:30 a.m. and 5:30 a.m. The valve releases excess air from the system. However, last week, the report said it instead released water for four hours. It was shut off when found. An investigation into the exact cause of the malfunction is currently ongoing. The report also mentioned that there is a wetland about 45 m east and south from the spill site and Shot Lake is 450 m to the northeast.

On Sept 6., an inspector for the project, Erika Nissen, responded to the report asking for clarification if the contaminated water reached the nearby wetland or Shot Lake. Nissen's other questions included whether or not the lake is fish-bearing, if there are plans to address any potential soil contamination and if arsenic was the primary contaminant of concern.

She also requested water samples from both the wetland and Shot Lake, photos of the spill site and to be informed of any further developments or reports.

CBC News reached out to the communications office with CIRNAC to find out if Nissens's questions are a part of the investigation or if they had been answered, but did not receive a response in time for publication.

CBC News also reached out to Parsons, the construction management company, however a response was not available at the time of publication.