Review of Good Mining Practices may include Tailings Dams. Vol 120

Introduction

The 2019 disastrous tailings dam failures of Rio Tinto’s Brazilian iron ore mine prompted a global response to review the lot of tailing dams. Indonesia has tailings dams, and also water dams, irrigation dams, flood control dams, earth retaining walls that are all regulated and managed by different, and overlapping ministries.

Perhaps some of Indonesia’ best known tailings dams include the Freeport process tailings in West Papua, and the Sidoarjo mud flow tailings wall in East Java. Many of Indonesia’s tailings dams are smaller, less well known, but still pose risks from nature (high rainfall and earthquake) and from potential inadequate management control. 

The release of the Global Review of Tailing Management is a timely opportunity for this article to take a brief look some aspects of the management tailings dams in Indonesia.

Global Review of Tailings Management.

The “Global Industry Standard on tailings management” was published in August 2020 by the International Council on Mining and Metals (ICMM), the United Nations environment programme, and Principals for Responsible Investment (PRI). The review is some 40 pages (English) with main chapters on Preamble, Global Industry Standard on Tailings Management, Affected Communities, Integrated Knowledge Base, Design, Construction, Operation and Monitoring of the Tailings Facility, Management and Governance, Emergency Response and Long-Term Recovery, Public disclosure and Access to Information, along with some annexes. The nature of this document seems to reflect a committee of expert’s approach, including unrelated quasi political points of view that may be inappropriate for some Indonesian operations.

Many of the report’s fundamentals are incorporated in existing best practices by most mining companies, and the existing Indonesian regulations. This Global Review may encourage some updating of the local best practices or regulations. The report may be of interest to “cherry pick” some points that may be suitable for the management of tailings dam’s in Indonesia. These might include; –

AMDAL – Demonstrate that project-affected people are meaningfully engaged throughout the tailing’s facility lifecycle. Prepare, document and update a detailed site characterisation of the tailings facility site(s) that includes data on climate, geomorphology, geology, geochemistry, hydrology and hydrogeology (surface and groundwater flow and quality), geotechnical, and seismicity. The physical and chemical properties of the tailings shall be characterised and updated regularly to account for variability in ore properties. Periodically review and refine the tailings technologies and design, and management strategies to minimise risk and improve environmental outcomes. Develop and document on the breach analysis for the tailing’s facility.

Design, Operation and Closure. – Develop preliminary designs for the tailing’s facility with external loading design criteria consistent with both the consequence of failure classification selected based on current conditions and higher Consequence Classifications (including ‘Extreme’). The Design Basis Report (DBR) details the design assumptions and criteria, including operating constraints, and that provides the basis for the design of all phases of the tailing’s facility lifecycle. Determine the consequence of failure classification of the tailings facility by assessing the downstream conditions. Undertake a Dam Safety Review (DSR) at least every five years, or sooner if there is a material change in the social, environmental and local economic context. The design should include progressive closure and reclamation. Manage the quality and adequacy of the construction and operation process by implementing Quality Control, Quality Assurance and Construction vs Design Intent Verification (CDIV). Prepare a detailed Construction Records Report (‘as-built’ report). Develop, implement, review annually and update as required an Operations, Maintenance and Surveillance (OMS) Manual that supports effective risk management approach. The Accountable Executive shall take the decisions to adopt a design, for the construction, and management of the tailing’s facility. This design, construction and establishment of a management plan should be subject to a senior independent technical review. 

Monitoring System. – Design, implement and operate a comprehensive and integrated performance monitoring programme for the tailing’s facility and its associated structures. Establish specific and measurable performance objectives, indicators, criteria, and performance parameters and include them in the design of the monitoring programmes that measure performance throughout the tailing’s facility lifecycle. Report the results of each of the monitoring programmes at the frequency required to meet company and regulatory requirements.

Management & Governance. – The Board of Directors shall adopt and publish a policy on or commitment to the safe management of tailings facilities, to emergency preparedness and response, and to recovery after failure. The Accountable Executive(s) shall be responsible for a programme of tailings management training, plus emergency preparedness and response. Appoint a site-specific Responsible Tailings Facility Engineer. Conduct regular reviews and audits to verify consistent implementation of company procedures, guidelines and corporate governance requirements in all aspects of tailings management. Prepare an emergency response plan, and conduct appropriate emergency response training.

An NGO Perspective of the Global Review report.

A report from “Earthworks” titled “Safety First: Guidelines for Responsible Mine Tailings Management” includes 16 recommendations that seem to be directed to the Brazil dam failure case. The review’s core emphasis of the recommendations is on ensuring the safety of communities located near mining operations. Further, the recommendations place legal responsibility for any incidents with corporate boards of directors.  In contrast, industry-generated recommendations from the Global Tailings Review do not place responsibility with the boards. Nor do they require private insurance for tailings dams, which the Earthworks report calls for.

Kepmen 1827 of 2018 about Good Mining Practices

This decree is dated 7 March 2018 and is 370 pages long. The decree mentions mine & process tailings in Article 2 Mine Feasibility Study, b 8 d) on the maps showing waste disposal sites (slag storage, tailings), and storage facility, plus article 8 for transport plans of tailings by pipe to be defined. Guidelines on implementation of environment management for mineral and coal mining, D 5 k mentions that the environmental activities are to include the requirement that tailings dams on land are to include management plans for emergency response and structural failure mitigation plans.  Guidelines 4 on reclamation and mine closure is to include tailings. Other guidelines for gold mines are to review gold content remaining in the tailings (including elevation, depth, location and historical data production of waste processing proceeds and purification of gold), and to make a technical review on the options of reprocessing such tailings.

ESDM revised Mining Law 3/2020 on Tailings

The new Indonesian mining law has very little to say specifically on tailings dams, and the term tailings is absent from within the definitions of Mining, Processing, Environmental Impact Assessment and Reclamation. Articles 6 & 46 announce that the government shall further determine laws and regulations, guidelines and criteria. The main article that approaches the tailings dam aspect seems to be Article 96. In the application of good mining technique principles, Mining Permit holders and Special Mining Permit holders must: b. Mining environmental management and monitoring, including Reclamation and Postmining activities; d. management of the waste of a mine from a Mining Business activity in solid, liquid, or gas form until it meets environmental quality standards before being released to the environmental media.

Ministry of Public Works [principally for water dams].

The dam safety was introduced in 1989 in Dam Safety Guideline issued by Ministry of Public Works which follows the implementation of Water Law No.11 of 1974. Further regulation regarding dam safety was issued in 1997 in Ministerial Regulation No. 72/PRT/1997 which states that dam development should have dam safety license from Ministry of Public Works and Housing and dam safety organization was formed.

Dam safety is comprised by: (1) structural safety, (2) Surveillance, (3) Emergency concept. Dam safety organization was formed to give recommendation to the Ministry of Public Works and Housing for a dam safety licence. Dam safety organization consists of dam safety commission (analyses) and dam safety unit (data collection, analyse and inspect). Structural safety is concerned about structural and operational failure, hydraulic failure, or seepage failure. Surveillance is to be undertaken regularly, with visual weekly checks and monthly instrumental readings or after extraordinary events, such as earthquakes etc. A dam safety organization and emergency plans needs to be in place. Administrative and technical design, operational program, rehabilitation and dam closure documents are to be lodged with the Dam Safety Unit.

The history of the Ministry of Public works includes some recent disaster dam failures. Near Jakarta, the Situ Gintung dam built by the Dutch catastrophically failed early on the morning of March 27, 2009. More than 100 people died and many more went missing. Newspaper reports mentioned some early warning signs were not acted upon, and confusion surrounded responsibility for this accident. Another dam burst in February 2019 that swallowed up thousands of homes and hectares of rice fields across South Sulawesi province, killing about 80 people and affecting more than 13,000 – the worst disaster in at least 15 years. The Makassar dam was completed in 1998 in order to prevent flooding.

Ministry of Environment on Toxic Waste.

Government Regulation 101 of 2014 on Hazardous and Toxic Waste Management follows the law 32 of 2009 on environment protection and management. This regulation has broad definitions for waste, hazardous waste, hazardous waste management, storage, emergency response system, environmental damage that may apply to some mining and processing companies’ tailings dams. Note the broad definition of; Hazardous and Toxic Materials (HTM) is any substance, energy, and or other component which due to its nature, concentration, may endanger the environment, health, and lives of man and other living creatures. The 233-page regulation includes aspects of determination of hazardous waste, hazardous waste storage, management, emergency response, guidance, supervision finance and administration.

Some Indonesia tailings dams

There are a few engineering consultants with expertise in the design and construction of Tailings dams that comply with Indonesian regulations and the miners long term needs. Technology to monitor tailings dam stability is available. Various computer-based data and management monitoring systems advertise Tailings Storage Facilities (TSF) systems for risk mitigation, design criteria and tailings management.

The following are some extracts of public announcements regarding tailings dams in Indonesia.

The Martabe Gold Mine, located approximately 40 km southeast of Sibolga in North Sumatra, Indonesia, is an operating gold mine that currently processes 4.5 Mt of gold ore per year. Co-disposal of waste occurs with all open pit mine waste utilized in the construction of the Tailings Storage Facility (TSF) embankment. The mine also includes a process plant, stockpiles, water treatment plant, sediment control dams, and several other facilities.

Specialist engineering design and construction services were engaged for the expansion of TSF to 60 Mt capacity. This included extensive 3D modelling of the embankment dam using software to assess stability under high seismic loading conditions. The updated tailings dam was re-permitted with the Indonesian regulators. Reports were also provided and presentations given to the Dam Safety Committee to successfully permit an expansion in capacity from 20 to 60 Mt.

PT Freeport Indonesia’s (PT-FI) Grasberg copper – gold mine is a world-class mining complex that is classified as a vital national asset and resource for the people of Indonesia and the Province of Papua. As a contractor to the government, the company is committed to the responsible stewardship and development of this resource, including the management of environmental and social impacts, both during and after the life of the mine. Tailings from this operation are the finely ground mineral rock that remain after the economically valuable minerals have been removed from the ore. The tailings management system involves the controlled riverine transport of tailings (and natural sediments) from the concentrator in the highlands to a large deposition area in the lowlands portion of the project area.

Freeport have published (2016) a 34 page report on “Controlled Riverine Tailings Management” that broadly outlines; • How tailings transport and deposition are managed in a controlled, engineered system; • Why it is the best management option for the physical and environmental setting; • What the impacts of the tailings management system are, and how they are monitored and managed; and • How PT-FI is preparing for eventual mine closure and reclamation of the tailings deposition area.

The Ministry of Environment and Forestry (LHK) issued a decree 175/2018 on the management of Freeport’s tailings on the 9 April 2018. The decree is 19 pages long. This decree updates and replaces the previous decree 431 / 2008 on Freeport’s tailings. The decree is very specific in being applicable to PT. Freeport Indonesia and is in relation to Freeports tailings in the Ajkwa river area. There is a 6-month transition period for the new tailings management system to be in place. The decree sets out technical criteria on the tailings area and its capacity, along with various testing programs on the nature of the tailings. These criteria include a 230Km2 area for the tailings area, with a tailings volume limit of 291,000 dry metric tons per day. The tailings area is divided into 3 zones, with specific requirements for each zone. Test samples are to be taken at 10 locations each with a 50m radius of representativity and tested for suspended solids, heavy metals and potential acid forming characteristics. Testing to be performed in the tailing’s river valley, adjoining sea and nearby water wells. Results to be reported to various director generals of the environmental ministry.

Vale nickel mines have increased its monitoring of dams, looking at ways to discharge less material into tailings dams, reducing the impact on society and environment, as reflected with increasing budget allocation for dam management.  Vale conducts reviews by external and independent companies periodically, to certify the dams’ physical and hydraulic safety conditions. These reviews also aim to meet the legal requirements provided in Brazilian standards and, we may expect Indonesian standards also.

Aneka Tambang Tbk Pongkor gold mine tailing dam research paper (Nov 2019) undertaken by the Diponegoro University. Construction of TSF (Tailing Storage Facility) dam was built to accommodate gold processing waste from UBPE (Gold Mining Business Unit) PT. ANTAM Pongkor. The construction of the TSF dam has been completed, but it still leaves some constraints regarding control, which in turn creates technical obstacles, namely the absence of land to accommodate tailings for the life of mine. The research found that the service level of the main dam is sufficient to accommodate rainfall with a return period of 2 years, but does not meet the development plan that can accommodate up to three years. To extend the service life or level, the authors suggest adding pumps and sludge dredging tailings. There are a number of scholarly articles on the Pongkor tailings dam.

Sebuku coal wash plant tailings design incorporated the installation of thickeners, to reduce the water entering the tailings dams.

Alternative Tailings Systems.

The vast majority of the world’s tailings facilities involve tailings impoundments to store tailings slurry with a solids content of about 25% to 60% depending upon whether any thickening is carried out prior to deposition. These impoundments require construction and maintenance of structural integrity for the retention structures as well as management for what are typically immense quantities of water. Alternative tailings management approaches can include “dry stack storage” options using new technology such as large capacity vacuum and pressure filter technology etc. Guidance documentation and regulations on filtered tailings is virtually non-existent.

Two nickel companies have requested to dispose of mining tailings into the ocean. Good environmental practices usually required deep sea tailings are piped and released at a depth of more than 100m. The feasibility and environmental study often may take considerable time and research.

Conclusion.

The Mines Department has mentioned in various public events its intention in going forward to focus on Good Mining Practices. The recently published “Global Industry Standard on tailings management” may be considered as one of the inputs towards Indonesia developing revised regulations on tailings dams.

There is apparent overlapping, and sometimes confusing, regulations by various ministers on tailings dams. Within Indonesia the concept of an omnibus law on dams is not yet developed.