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Newcrest Mining has received the final report from the Independent Technical Review Board (ITRB) following the tailings dam embankment slump at its Cadia gold operation in New South Wales last year.
The slump occurred on March 9 in the southern wall of Cadia’s Northern Tailings Storage Facility, causing it to lose containment of the section’s tailings.
It did not result in any injuries or environmental damage as the tailings released were captured in the bordering Southern Tailings Storage Facility (STSF).
The ITRB report found that the main factor determining the location of the slump was the existence of a low-density foundation layer in the slump’s vicinity.
The layer material was found to be relatively weak and highly compressible and brittle once subjected to a significant load.
It was the failure of this weak foundation material when placed under load accumulated over time that resulted in the deformation of the wall.
This then triggered the liquefaction of part of the tailings behind the embankment causing it to slump forward.
Other mitigating factors included the local height of the dam, the prevailing low pore water pressure and the excavation at the toe of the structure in the area of the slump.
The ITRB recommended that Newcrest continue to enhance the level and type of monitoring equipment, particularly in the foundations of the tailings storage facilities.
Newcrest has engaged expert engineering firms to confirm that the STSF remains safe to operate.