Sustainability

Dams and tailings management

Newcrest recognises that good environmental practice is critical to good operational performance and to building community trust and acceptance. 

Waste rock and tailings management are paramount considerations in our safety and risk reviews, project development assessments, and land rehabilitation and mine closure planning and implementation.

Background

Tailings are the resulting material from finely-ground processed ores that have been through a number of sizing, grinding, and processing steps. 

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

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

Tailings Storage Design

Every location of our mines is unique and, as such, our tailings facilities are designed to take into account a range of factors including the local topography and climate, the geotechnical, geological and seismic activity, its proximity to people and infrastructure, land rehabilitation, and future land use considerations.

There are three main tailings construction methods:

  • Downstream design continues the construction of the embankment wall on the external side of the compound with the batter extending on to what we call natural surface (or land that previously has not been disturbed), by depositing more support rock and bunding against the previously built tailings wall, thereby expanding the footprint, width and height of the initial embankment wall.
  • Centreline design involves the continuation of the embankment construction on the external side of the compound however, does rely on the deposited tailings adjacent to the top of the initial embankment wall to support the raises.
  • Upstream design allows the embankment wall to be constructed on the inner side of the compound and relies on the strength of the deposited tailings to support the structural material for each lift of the embankment. This method allows for smaller quantities of earth and rock fill to be built on top of the tailings and therefore does not expand the footprint of the facility.

Over a number of years each new tailings wall moves upwards creating a layered or contoured hill for all methods. The tailings wall needs to lift to allow the facility to contain the design capacity of tailings being generated by the operation, and to reduce the overall land disturbance of tailings placement.

NEWCREST TAILINGS FACILITIES

As of 30 June 2020, Newcrest had 12 terrestrial tailings storage facilities. Three of these were in active use; two are inactive and under short-term care and maintenance and will resume operations following improvements;

and seven are under long-term care and maintenance.

  • Red Chris has one tailings storage facility in operation, contained by two dams, based on centreline design.
  • Telfer, in Australia, has one facility in operation with six small facilities no longer in use. The operating TSF commenced as downstream design and has had lifts added in an upstream configuration.
  • Cadia, in Australia, has three facilities. The Cadia Hill open pit is being utilised as a tailings facility. The 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 dams 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 TSF.

Lihir in Papua New Guinea (PNG) uses the DSTP method, approved by the PNG Government, given a lack of suitable terrestrial tailings storage options due to high rainfall, frequent seismicity, and use of land for farming. Lihir has nearshore slopes leading to a deep ocean basin with an absence of upwelling; this meets industry criteria for the application of DSTP.

Newcrest’s Sustainability Report provides more detail on the Company’s tailings management approach and program, as well as data on extraction rates and the tonnage of waste rock and tailings generated at each site during mine production.

Tailings Management System

Tailings are managed within engineered tailing storages. Risk is managed through completion of engineering designs in accordance with leading practice guidelines (e.g., ANCOLD 2012), safety assurance through independent review, and 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. This Framework is aligned to the International Council on Mining and Metals (ICMM) Position Statement on Preventing Catastrophic Failure of Tailings Storage Facilities.

The Tailings Management Framework has been implemented at operations by undertaking a mapping exercise and identifying required improvements, which are being progressively addressed.

REVIEWS AND INSPECTION

Newcrest’s tailings storage facilities are audited against criteria that aligns with industry guidelines and specifically against the Australian National Committee on Large Dams (ANCOLD) guidelines.

All of Newcrest’s operations have a program of annual external audits. Like most major mining companies, Newcrest commissioned a series of independent audits of its tailings storage facilities following the Samarco event in 2015. 

In response to Cadia’s Northern Tailings slump in 2018 Newcrest is conducting even more extensive reviews on all its tailings storage facilities.  Read the findings of the independent review into the technical root cause of the slump, which have all been accepted by Newcrest.

At Cadia we have conducted investigative drilling near tailings storage facility walls with a significant number of samples tested and analysed. There has been a detailed review of the geological mapping. Engineering work conducted over life of tailings wall has also been reviewed. 

In 2018 Newcrest commenced construction of buttresses in two areas of the Southern Tailings Storage Facility (STSF), which have now been completed. In designing this buttressing, Newcrest and its external engineers have assumed the potential presence of weak material analogous to that in the area of the Northern Tailings Storage Facility (NTSF) slump and adopted conservative strength parameters.

We are also concluding the design of future STSF raises to progressively move from upstream to centreline. Construction is planned to begin in late 2020. Meanwhile, our work is progressing on the repair plans for the NTSF.

Investigations to reconfirm the TSF design at Telfer began in May 2018, under the supervision of acknowledged industry experts.  As part of this investigation, cone penetrometer tests have been conducted on the TSF to validate design assumptions. Work is ongoing in relation to ensuring the stability of the Telfer TSF.

Tailings storages with upstream construction have been subject to analyses to confirm the engineering characteristics of the tailings and with a view to confirming tailings saturation. Several dams have been reinforced with buttresses or are now subject to panel review where such has been recommended.

Our strong commitment to the safety of people and care for the environment underpins our approach to managing our tailings facilities. There is nothing more important to Newcrest than everyone going home safe every day, the safety of our local communities and the environment.

Global Cooperation

Newcrest is a member of the ICMM which is taking an industry leadership role on tailings management.

In February 2019 the ICMM, the Principles for Responsible Investment (PRI) and the UN Environment Programme began developing the Global Industry Standard on Tailings Management. The standard, launched on 5 August 2020, was developed through an independent expert panel that reviewed current mining industry global best practices for designing, managing and operating tailings storage facilities.

As a member of ICMM, we participated in the development of the standard with other stakeholders. Newcrest is working to align the Newcrest Tailings Management Framework with the Global Industry Standard on Tailings Management and implement changes at our operations as required.

Newcrest has published its tailings facilities details in the Global Tailings Portal ensuing from the Investor Mining and Tailings Safety Initiative. This database allows investors to find information submitted by mining companies about tailing facilities and the impact of climate change and extreme weather events on dam stability. We support the increased transparency this database provides to our stakeholders.