Dams and tailings management

Tailings are the resulting material from finely-ground processed ore bearing rock that has been through several sizing, grinding, and processing steps.

Tailings are discharged as dense slurry into containment areas known as tailings storage facilities (TSF) or through deep sea tailings placement (DSTP) in suitable deep-ocean locations. Modern gold and copper processes seek to maximise the extraction of economic minerals, chemicals and reagents before the tailings are deposited.

Under Newcrest’s World Gold Council membership, Telfer and Lihir are certified to the International Cyanide Management Code, while Red Chris and Cadia do not use cyanide for processing.

Every mine location is unique with tailings facilities designed to account for a range of considering factors including:

• Local topography;
• Climate;
• Geotechnical and geological conditions;
• Potential seismic activity,
• Proximity to people and infrastructure;
• Land rehabilitation and;
• Future land use considerations.

The three main TSF construction methods are:

• Downstream construction involves raising the dam by placing fill on the downstream side of the initial embankment. This construction method requires the embankment to be expanded over previously undisturbed ground and requires the largest amount of fill for a given height increment.
• Centreline construction also requires fill to be placed on the downstream side of the embankment, but the raised crest remains vertically in line with the previous crest. This construction method requires less fill than the downstream method but relies on the support of the upstream tailings to some degree.
• Upstream construction involves embankment construction over previously deposited tailings and relies on the strength of the tailings for the stability of the embankment. This construction method uses the least amount of embankment fill and does not require the footprint to be expanded.

Tailings facility embankments are either continually or incrementally raised in layers or lifts to contain the tailings generated by the operation and to minimise the area of land disturbed by tailings placement.

As of 30 June 2020, Newcrest had 12 terrestrial tailings storage facilities.

• Three tailings facilities in active use;
• Two tailings facilities inactive and under short-term care and maintenance with operations resuming following improvements;
• Seven tailings facilities under long-term care and maintenance;

• One tailings storage facility in operation at Red Chris, contained by two dams, based on centreline design.
• One facility in operation and six smaller facilities no longer in use at Telfer. The operating TSF commenced as downstream design and has had lifts added in an upstream configuration.
• Three facilities at Cadia.
  • Cadia Hill open pit is being utilised to store tailings.
  • Northern Tailings Storage Facility (NTSF) and
  • Southern Tailings Storage Facility (STSF), which both commenced as downstream design, have had lifts added in upstream configurations. Both TSFs are currently inactive. At Blayney near Cadia, there is a historic copper mine and an associated small remnant tailings facility that is currently under care and maintenance.

In Ecuador, Newcrest has an equity interest in Lundin Gold which operates the Fruta Del Norte gold project and its downstream-constructed TSF.

Given a lack of suitable terrestrial tailings storage options, high rainfall and frequent seismicity at Lihir, the Papua New Guinea Government has approved the DSTP method with near offshore ocean slopes leading to a deep ocean basin with an absence of upwelling; conditions that satisfy industry criteria for the application of DSTP.

Where tailings are discharged into TSFs, risk is managed through completion of engineering designs in accordance with leading practice guidelines (e.g., ANCOLD 2019), safety assurance through independent review, and by following Newcrest’s internal risk and change management procedures.

Newcrest’s commitment to safe and responsible tailings facility operations is documented in the Tailings Management Framework and required by Newcrest’s Tailings and Water Storage Standard.

These documents are aligned to the International Council on Mining and Metals (ICMM) Preventing Catastrophic Failure of Tailings Storage Facilities Position Statement and the Global Industry Standard on Tailings Management (GISTM).

Newcrest’s TSF is audited and aligned with industry guidelines, specifically the Australian National Committee on Large Dams (ANCOLD) guidelines.

Following the Samarco event in 2015, all of Newcrest’s operations conduct annual external audits with a series of independent audits commissioned of its TSFs.

Cadia
In response to Cadia’s Northern Tailings slump in 2018, Newcrest accepted the findings of the independent review into the technical root cause of the slump and have conducted extensive TSF reviews.

Extensive investigative drilling completed along containment embankments included a significant number of samples tested and analysed. A detailed review of the geological and geotechnical model design includes engineering work conducted over the tailings life cycle facilities.

In 2019 Newcrest constructed buttresses in two areas of the Southern Tailings Storage Facility (STSF) to enhance embankment stability in these areas. In designing this buttressing, Newcrest and external engineers assumed the potential presence of weak material analogous identified in the area of the Northern Tailings Storage Facility (NTSF) slump and adopted conservative strength parameters. Future raises to the STSF will transition away from upstream construction to centreline construction. This process commenced with the construction of STSF Stage 7 in early 2021 with repair work progressing for the NTSF.

Telfer
Investigations to reconfirm the TSF design began in May 2018 under the supervision of acknowledged industry experts.  As part of this investigation, cone penetrometer tests have been conducted to validate design assumptions with ongoing work planned to ensure the stability of the Telfer TSF, and a second TSF under construction will further improve Telfer’s tailings management.

The Tailings storages with upstream construction and supporting tailings has been assessed for engineering characteristics, with a view to confirm tailings saturation. Several dams have been reinforced with buttresses or subject to panel review recommendations.

Newcrest is working closely with peer companies, industry associations, governments and communities to support and implement the Global Industry Standard on Tailings Management (GISTM) Standard.

The GISTM is dedicated to leading tailings management and committed to making significant steps towards safer and more responsible tailings facility management.

Together with the ICMM, Principles for Responsible Investment (PRI) and the UN Environment Programme, the GISTM was first developed in response to the tailings failure of the Dam at Córrego do Feijão near Brumadinho, Brazil in January 2019.

Newcrest’s role in the GISTM development ensures our Tailings and Water Storage Standard is aligned and the new Tailings Management System is fully compliant, superseding the Tailings Management Framework.

Newcrest publishes its tailings facility details in the Global Tailings Portal database allowing investors and stakeholders to review tailing facilities, the impact of climate change and the extreme weather events on dam stability.

As a responsible mining company and member of the ICMM, Newcrest Mining is committed to implementing GISTM.

The GISTM strives to achieve an ambitious zero harm to people and the environment by requiring operators to prioritise the safety of tailing facilities throughout all phases of the facility’s lifecycle.

The GISTM was launched on 5 August 2020 following a Global Tailings Review – an independent review process co-convened in March 2019 by the United Nations Environment Programme (UNEP), Principles for Responsible Investment (PRI) and the ICMM in response to the tailings failure of Dam I at Córrego do Feijão near Brumadinho, Brazil in January 2019. It aims to prevent catastrophic failure of tailings facilities by providing operators with specified measures and approaches for safe tailings facility management.

Newcrest is determined to play its part in making tailings facilities safer, and is working closely with peer companies, industry associations, governments and communities to support and implement industrywide improvements to tailings facility management.

Newcrest’s implementation of the  GISTM will follow a phased approach.  As part of our commitment, any tailings facilities operated by Newcrest with potential consequences assessed as being “extreme” or “very high” will conform with the Standard GISTM by 5 August, 2023. All other tailings facilities operated by Newcrest, excluding those in a state of safe closure, will conform with the Standard GISTM by 5 August 2025. We are also in the process of updating internal management and governance systems that include standards and guidelines to align with the GISTM.

Newcrest has welcomed the release of the GISTM as a significant step towards strengthening current practices in the mining industry to support safer and more responsible tailings facility management. We are proud to be part of the Standards development and our focus has been on implementing the Standard through our ICMM membership commitment.

For further information on the GISTM, visit the Global Tailings Review.