TAILINGS OVERVIEW
Phu Bia Mining operate two Tailings Storage Facilities (TSFs), Phu Kham TSF and Ban Houayxai TSF. TSFs are structures used to safely store waste by-product (tailings) material from the processing plant. Tailings dams are different to hydroelectric dams. The main difference is hydroelectric dams are typically completed to their final elevation during initial construction, whereas tailings dams are incrementally raised (typically annually or bi-annually) in ‘stages’ over the life of the mining operation in line with the rate of tailings produced. The staging of the facilities is based on tailings production rates and must consider seasonal (weather) and construction practicalities.
Both of Phu Bia Mining’s (PBM) TSFs comprise an earth/rock fill cross valley main embankment, saddle dams and spillways. The embankments are earth/rock fill embankments which include a low permeability zone, internal filter zone and downstream coarse structural zone. PBM’s TSFs are constructed using the downstream method of construction which are generally recognised by the mining industry as the safest form of embankment construction when compared to centreline or upstream construction. The three construction methods are shown schematically below:
Both Phu Kham (PKM) and Ban Houayxai (BHX) TSFs have engineered spillway structures designed to safely pass the Probable Maximum Flood (PMF) which is equivalent to a 1:10,000-year recurrence flood event. Appropriate treatment and environmental monitoring are in place to show any discharged water is in compliance with industry regulations.
The TSFs are designed, constructed and operated to the international standards of the International Commission on Large Dams (ICOLD) and the Australian National Committee on Large Dams Incorporated (ANCOLD).
The key characteristics of the two TSFs are presented in the table below:
| Characteristics | PKM TSF | BHX TSF |
|---|---|---|
| Status | Active | Active |
| Years in Operation | 16 (2008) | 12 (2012) |
| Height: Current/Final | Main Embankment: 185m/185m | |
| Western Saddle Dam: 20m/20m | Main Embankment: 91m/99m | |
| Spillway Saddle Dam: 34m/34m | Saddle Dam: 39m/37m | |
| Eastern Saddle Dam: 10m/10m | ||
| Design Storage | 240 Mt | 84 Mt |
| Tailings Production Rate | 10 Mtpa | 5 Mtpa |
PHU BIA MINING APPROACH
Phu Bia Mining is committed to environmentally and socially responsible tailings management to minimise health and safety impacts to people and the environment.
A comprehensive Tailings Management System is in place that includes the PanAust Tailings Governance Standard, Tailings Review Committee Charter and Phu Bia Mining Operations, Maintenance and Surveillance Manuals. The Governance Standard clearly defines accountabilities and responsibilities, principles and standards, and encourages continuous improvement as progressive advancements are envisaged to enhance long term safety and environmental performance. PanAust Tailings Governance Standard is based on international guidelines, including MAC, CDA, ICOLD, ANCOLD and GISTM.
PanAust has appointed roles that align with the Global Industry Standard on Tailings Management (GISTM). The General Manager of Technical Services and Studies is the appointed Accountable Executive and is accountable for the safety of the tailings facilities. The appointed Responsible Tailings Facility Engineer (RTFE) is the Tailings and Geotechnical Manager. The RTFE is accountable for the integrity of the tailings facilities and is familiar with the design basis, design report and the construction and performance of the tailings facility.
A Tailings Review Committee (TRC) is utilised at PanAust to co-ordinate Governance and Management of the TSFs to ensure that strategy and decision making can be practically implemented. The TRC objectives include informing the Executive Chairman about material risks, overseeing actions related to material risks and providing the necessary support and resources, and agreeing strategic decisions pertaining to the TSF. The TRC is an internal function and the members include the General Manager of Technical Services and Studies, General Manager of Operations, Tailing and Geotechnical Manager, Risk Manager, PanAust Group Manager of Risk and Sustainability and TSF Superintendent.
An experienced Engineer of Record (EoR) has been appointed from reputable engineering firm. The EoR overseas the design and construction of the Tailings Storage Facilities and is responsible for engineering inspections and associated reports. The EoR provides ongoing support to the Phu Bia Mining Tailings team and has regular contact with Phu Bia Mining Engineers, including weekly meetings. The EoR performs three inspections annually, including the Annual Dam Safety Review (ADSR). Independent reviews are also undertaken annually by the Tailings Independent Review Panel (TIRP), experts in the field of tailings management, and a third-party Comprehensive Dam Safety Review is completed by a reputable engineering firm every three to five years.
To align with GISTM disclosure requirements PanAust publish a disclosure report meeting the GISTM Requirement 15.1 B for the Phu Bia Mining tailings facilities. The latest disclosure reports can be downloaded from the following links:
