There are many international guidelines, state regulations and technical standards relating to tailings disposal. In addition, the larger mining companies have their own in-house standards and design rules with competent personnel in charge of their operations. Sound embankment design methods can be used by most designers familiar with earth dam design.
The paper gives a listing of many of the current sources of information and guidance available, with some comments by the author on their perceived relevance to the Australian mining industry. Despite the availability of a number of other guidelines at the time, the need for Australian Guidelines was recognised in the mid 1990s and the reasons for the development of the 1999 ANCOLD Tailings Guideline are explained.
Perhaps the best recognition of the need for the original ANCOLD guideline is the degree to which it has been adopted since publishing the 1999 edition. It is in almost universal use in the Australian mining industry and is recognised as providing appropriate and acceptable standards by all state governments. Its use is recognised and sometimes even specified by a number of neighbouring countries and it is also recognised internationally when used by Australian companies with overseas operations.
The reasons for this wide acceptance are described. However, there are some areas where more recent developments have led to the Guidelines becoming dated and improved international guidelines have been published since 1999. The need for a revised ANCOLD guideline and its elevance is then described.
Keywords: Tailings, dams, mining, guidelines
Russell Paton, Peter MacTaggart, Lee Benson
The Nathan Dam project has been identified by the State Government of Queensland as a potential water supply option to facilitate future growth in central Queensland. The proposed storage is located approximately 69 km downstream of the township of Taroom and would have a storage capacity of 1,080,000 ML which would make it Queensland’s fourth largest storage.
The proposed dam arrangement includes a central concrete gated spillway section across the river in order to maximise the storage volume and limit the flood rise upstream such that flood levels at Taroom are not increased during major flood events. A high level fixed crest spillway, to assist in the passage of rare flood events, forms the right abutment portion of the dam wall. It is proposed that the bulk of the concrete sections of the dam be constructed using roller compacted concrete (RCC).
The investigations to progress Nathan Dam are complicated by the existence of the Boggomoss Snail (Adclarkia dawsonensis) within the proposed inundation area. The snail is listed as a critically endangered species under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), and a proportion of the snail’s known population is located on a Boggomoss (the colloquial name for an artesian spring) that will be inundated should the project proceed.
SunWater has engaged Australia’s foremost expert on land snails to design a translocation process aimed at relocating the species to alternative habitat outside the inundation area. The process will seek to not only protect the snail from the dam development, but to increase both its numbers and distribution thereby reducing risks to the currently isolated population from threats such as fire and predation. It is the first time in Australia that such a trial has been attempted, and SunWater is working closely with the Federal Department of Environment, Water, Heritage and the Arts (DEWHA) to ensure that the process is consistent with their policies and guidelines.
The paper will discuss the engineering and environmental challenges of the dam and how the Environmental Impact Study process can influence the delivery of a project.
Keywords: Nathan Dam, Environment, Engineering
Alice Lecocq, David Brett, Mike Rankin
Tailings Dams class amongst the world’s largest man made structures. They are interactive structures that evolve over time, with tailings discharge, water management, embankment raising and finally closure and abandonment. Understanding of the design, the impact of operations and regular, committed surveillance is essential to ensure the safety and performance of a tailings dam. Dam Safety Management Plans should be developed to optimise these parameters. These plans should include Operation, Maintenance and Surveillance (OMS) manuals, emergency response plans and monitoring databases. They should be managed by the mine management and implemented by the operations personnel.
The tailings dam operators are the key to a successful dam safety management program. It is imperative that the tailings dam management and operators appreciate the risks inherent with the facility, their role and their responsibilities. They also need to have an appropriate understanding of the tailings dam design features, failure modes and safety triggers. With training it is expected that personnel will be better able to recognise and act on safety issues arising.
The paper presents case histories of tailings dam failures due to poor operation and management and outlines the operational requirements and risks inherent with tailings dams. The paper discusses the training approach and criteria to be adopted, and describes a training course developed by the authors for mine management and operators. The paper examines the feedback collected from the courses held at several mines. A model to successfully implement a surveillance program with the involvement and leadership of the operators is proposed.
Keywords: TSF failures, surveillance program, OMS manuals, training of personnel.
Dr Azan Khan, Ahmad Nasir, Kumud Kandel, Jaya Kandasamy, Hadi Khabbaz, Mahub Ilahee
Cracking in the clay core of embankment dams is important to dam safety because it can cause seepage through transverse cracks and with excessive seepage cracks may begin to erode the soil on the sides of the crack. If there are no filters to control this erosion, the erosion may progress to form a pipe, eventually leading to breach of the dam. Recent climate change has resulted in long term drought conditions in various parts of Australia, especially west of the Dividing Range. The prolonged drought conditions can lead to the loss of moisture content in the clay core causing cracking of the core material. The current research is investigating a relationship between long term drought condition and loss of moisture content in the clay core. This paper presents the loss of moisture content in the clay core of three dams in Australia due to global warming. A rigorous finite element modelling has been conducted to capture the moisture content changes in a typical large clay core dam.
Keywords: clay core, dams, climate change, moisture content
Jonathon Reid, Chris Kelly, Bob Wark
One of the most important aspects in the construction of an embankment dam is to be confident that the filter materials placed meet the design intent. The design methodology for filters is now well documented.
However, all too often during construction the filter material, as placed, does not comply with the specified requirements and all parties are faced with costly decisions and delays to the works to determine correction measures and whether the work completed meets the design intent. This paper shares the knowledge gained over a number of projects the authors’ have been involved in and the methods used to improve the properties of the placed filters taking into account some of the practicalities of having these materials produced and placed in a commercial environment
Keywords: filters, specifications, manufacturing, construction, quality assurance.
Shane Papworth, Stuart Richardson, David Dreverman, Mel Jackson
A prominent element of the operational environment of a dam is its interaction with the community.The management of public recreational use of irrigation storages is an increasing challenge for Goulburn-Murray Water and the Murray Darling Basin Authority. The upper Murray storages have been significantly affected by the unprecedented low water resource availability which has caused an increasing conflict between the primary use of the dam to supply irrigation water and the secondary benefit of recreation and tourism use by the local communities. Many difficult management issues (media, community relations, political interest) arise from the local community, rather than just from operation of the dam itself.
An increasing awareness of the dire water resource position in recent years has coincided with an ever increasing appreciation of the environmental and social impacts of recreational use. For the storages along the Murray system, effective management is further complicated by complex agency and authority responsibilities, communities and interest groups effectively ‘in competition’ for the water resource.
To better manage these issues, ‘Land and On-Water Management Plans’ have been developed for Lake Mulwala and Lake Hume. Developing the Plans has not been without controversy, but ultimately the Plans have proved to be a simple and successful means of planning for and achieving agreed land and water management outcomes. This in turn is fostering a positive spirit of cooperation and communication with communities currently under considerable stress as a result of prolonged drought.
This paper describes the process, pitfalls and learnings to come out of the development of the Land and On-Water Management Plans.
Key words: Environment, community, irrigation dams, recreational use, planning