Effluent from a mine at Rosebery has leaked into the Stitt River following a problem with a new dam.
MMG Rosebery discovered on October 10 water was leaking from a screening bund at its six-month-old tailings storage facility on the Murchison Highway near Gepp Street.
An MMG spokesperson said the company became aware “of a minor discharge into the Stitt River following recent rainfall”.
“On learning this, we immediately notified the regulator and we are seeking independent advice to identify the source and determine the appropriate management action,” the MMG spokesperson said.
“We have also implemented a temporary water diversion to redirect the discharge water back to the treatment plant.”
MMG said in a letter to Rosebery residents that the water diversion was installed to “redirect the discharge water back to the treatment plant and to reduce discharge to the Stitt River”.
“A more permanent solution is currently being designed,” MMG wrote in its letter.
The company said it had also undertaken environmental testing, groundwater modeling and a technical investigation “to determine the cause of the discharge and develop a permanent mitigation strategy”.
“To date, the water diversion has significantly reduced the amount of discharge and this will continue to reduce over the coming days,” MMG wrote.
“Our technical teams are advancing the actions outlined above in consultation with relevant authorities.
MMG is committed to managing the environmental risks and impacts of our operations.
The MMG spokesperson said the company took environmental management “extremely seriously” and had been working with the West Coast Council.
It has also contacted the Environmental Protection Authority and has continued to provide it with environmental sampling and reports.
An EPA spokesperson said the government agency had spoken to MMG last week “after rain may have contributed to some possible seepage from a tailings dam on site”.
“The company has advised the EPA that it has put in place a number of measures to address the seepage and investigate it further,” the EPA spokesperson said.
“The EPA will continue to liaise with the company as it addresses the issue.’’
MMG commissioned its new tailings storage facility at Rosebery in April 2018.
The company said it had established a “comprehensive environmental monitoring network” and carried out “regular monitoring is carried out in line with regulatory requirements”.