Taseko Mines Ltd. states it has determined that Natural Resources Canada (NRCan) used the wrong design in its analysis of the proposed New Prosperity Mines tailings storage facility, leading the federal review panel to incorrect findings.
One of Taskeo’s top project engineering consultants, Knight Piesold, advised the mining company last week that NRCan, and subsequently the environmental review panel, used an incorrect design in its analysis of potential seepage rates from the tailings storage.
That design was apparently missing a crucial, low-permeability compact soil liner to restrict seepage losses.
Taseko vice-president of corporate affairs Brian Battison says the government of Canada now has a “flawed finding” in the panel’s report, recently submitted to Environment Minister Leona Aglukkaq.
The panel’s finding that the tailings storage facility would eventually lead to significant seepage into Fish Lake was strongly based on the modelling provided by NRCan, he explains.
“It is clear now that NRCan relied on the wrong design in its analysis, and then the panel relied on this wrong information to draw conclusions in its report.
“The bottom line here is this calls into question the validity of the panel’s findings of significant adverse environmental impacts on fish, fish habitat, wetlands and Aboriginal interests in the Fish Lake area.”
Once the panel released its report, engineers at Knight Piesold and Taseko narrowed their focus to explore particular areas of concern, he explains.
While NRCan’s use of this erroneous information has been confirmed by both companies, Battison says no government or other regulatory body has yet corroborated the evidence.
“It’ll take them some time to examine what happened and who did what.”
Battison says the correct tailings facility design, which includes a vital pond liner to control seepage, is “very similar” to the Mount Polley and Mount Milligan mines.
Without that liner, tailings seepage would readily leak into the ground and fractured bedrock, he explains.
Knight Piesold’s design for Mt. Milligan won the Thompson Creek Metals Company an award of merit from the Association of Consulting Engineering Companies-Canada, the Battison adds.
“So, that design now is being held up by the Ministry of Energy and Mines as the new standard for mines in B.C. … like ‘best practices’.
“Our design [uses] the same principles. We were expecting our conclusions to be confirmed by the panel, and when they weren’t, it was a surprise.”
This is when Taseko realized the panel had “made a mistake,” Battison explains.
“Knight Piesold [engineers] are the ones that discovered this. Like us, they were very puzzled by the results of the panel report, and ‘how did they get this so wrong’. So, then there was a detailed examination by them to try and discover where the mistake was made … and our own engineers confirmed it.”
Taseko president and CEO Russell Hallbauer says the company has advised Aglukkaq it will challenge certain aspects of the panel’s findings, and asked that she receive and consider additional information prior to making any decisions on significant environmental effects.
The liner is a “common and acceptable practice for modern facilities” both in British Columbia and elsewhere in the world, he says, adding Knight Piesold is a preeminent engineering firm among the best in the world.
The Canadian Environmental Assessment Agency, which is the responsible federal authority, replied it will not comment on the panel report at this time.
