Mine Pit Lakes in Australia: an International Perspective

Naresh Kumar(MiWER), Clint McCullough (MiWER), Mark Lund (MiWER)

What are the characteristics of Australian pit lakes and how do compare to those of other countries?

The MiWER team were invited to contribute a book chapter on “Mining lakes in Australia” to the book, “Acidic Pit Lakes – legacies of coal and ore mining” published by Springer. The book is a revised version of the now 10 year-old well-recognised publication by the same publishers. Our chapter will highlight knowledge of mine pit lakes in Australia. Main topics that are covered in the chapter are the total number of mine lakes, type of mining, physical, chemical and some biological characteristics, any remediation and rehabilitation approaches planned or already carried out, remediation drivers and the socio-economic aspects of the mine lakes etc. To assist us, we have contacted regulatory agencies in all states as well as a broad range of industry groups and consultants to provide information on pit lakes across the country.


Photo: Australia has many highly acidic and also highly saline lakes as a result of its arid climate. Mine from the Goldfields of Western Australia.


Map: With a mining booming in Australia, mine pits are forming larger and more ubiquitous pit lakes than ever before.

Outputs

Kumar, N. R.; McCullough, C. D. & Lund, M. A. (2012). Pit lakes in Australia.In: Acidic Pit Lakes – Legacies of surface mining on coal and metal ores. (Ed W. Geller & M. Schultze). Springer, Berlin, Germany. 342-361pp.link

Kumar, N. R.; McCullough, C. D. & Lund, M. A. (2009). Water resources in Australian mine pit lakes. Proceedings of AUSIMM Water in Mining 2009Australasian Institute of Mining and Metallurgy (AusIMM), Perth, Australia. pp. 507-511.PDF

Kumar, N. R.; McCullough, C. D. & Lund, M. A. (2009). Water resources in Australian mine pit lakes. Mining Technology. 118: 205-211.link

Geochemical Modelling of Pit Lake Water Chemistry to Support Management Decisions

Mike Mueller (Hydrocomputing, Germany), Katja Eulitz (Hydrocomputing, Germany), Clint McCullough (MiWER), Mark Lund (MiWER)

How does pit lake water quality and depth change under different management scenarios?

Stage 1. Selection of appropriate model

This model will maximise the use of the currently available data for model creation and validation. The current preference is not to focus on a single pit lake and model in detail but develop a simpler model that can be easily applied to cohorts of Collie pit lakes identified by the inventory collection and conceptual modelling. This general model would be less detailed but more suited to the low input knowledge environment of the Collie groundwater region and would support important pit lake and ground water management decisions.

Stage 2: Model parameterisation and testing.

There is no option for detailed validation of the model at this stage, other than through use of existing historic and collection of new data sets arising from Task 1.

Stage 3: Scenario testing.

A series of different scenarios will be run to demonstrate model outputs and to test alternative pit lake management and environmental strategies for the different pit lake cohorts.

 

    

Figure: Important processes in pit lakes


Model: Schematic of model coupling in MODGLUE

Modelling Tools

This project is using the model PITLAKQ which is a coupled model that combines the groundwater model PCGEOFIM, the lake hydrodynamic and water quality model CE-QUAL-W2 and the hydro-geo-chemical model PHREEQC.

PITLAKQ is capable of modelling all processes that are important to pit lake water quality. Fig. 2 shows these processes that include weather induced hydrodynamics with thermal layering, heath and gas exchange with the atmosphere as well as flow, transport and chemical changes in the subsurface. In addition, a wide variety of water quality processes in the lake water such as biological processes including algae growth and nutrient dynamics as well as equilibrium and kinetic chemical reactions can be modelled. Pit lake specific chemical reactions may be defined by means of an extendable hydro-geo-chemical database and rate limited reaction paths.

PITLAKQ has already been applied to a variety of different mining pit lakes under different scenarios, producing results to guide surface and groundwater management.


Video: Model of Lake Kepwari during filling showing temperature changes


Video: Model of Lake Kepwari showing pH changes during filling

Outputs

Müller, M.; Eulitz, K.; McCullough, C. D. & Lund, M. A. (2010). Mine Voids Management Strategy (V): Water Quality Modelling of Collie Basin Pit Lakes. Department of Water Project Report MiWER/Centre for Ecosystem Management Report 2010-10, Edith Cowan University, Perth, Australia. 95pp. Unpublished report to Department of Water. link

McCullough, C. D.; Müller, M.; Eulitz, K. & Lund, M. A. (2011). Modelling a pit lake district to plan for abstraction regime changes. Mine Closure 2011: Proceedings of the Sixth International Conference on Mine Closure. Lake Louise, Canada. Fourie, A. B.; Tibbett, M. & Beersing, A. (eds.), Australian Centre for Geomechanics (ACG), Perth, Australia, 581-592pp. PDF

Müller, M.; Eulitz, K.; McCullough, C. D. & Lund, M. A. (2011). Model-based investigations of acidity sinks and sources of a pit lake in Western Australia. Proceedings of the International Mine Water Association (IMWA) Congress. Aachen, Germany. 41-45pp. PDF

 

Conceptual Modelling of Pit Lake Processes and Ecological Risk

Clint McCullough (MiWER), Mark Lund (MiWER)

Conceptual modelling to better understand ecological risks posed by pit lakes

To ensure greatest scientific robustness of conceptual models we held a site visit and workshop in Collie with an expert panel of scientific researchers and managers from universities and State regulatory staff to best understand how these processes are likely working in different pit lakes. This workshop identified conceptual model needs e.g., a carbon cycling model and an acidity budget model. The intent is to then present the conceptual models as diagrammatic representations highlighting the nature of relationships between parameters and processes. These models will also be used to develop cohorts of similar pit lakes for later empirical modelling.


Photo: How does acidity enter Collie pit lakes? (Lake Kepwari)


Figure: Example conceptual modelling of pit lake chemistry

Funding: Department of Water (Western Australia)

Outputs

McCullough, C. D. & Lund, M. A. (2010). Mine Voids Management Strategy (IV): Conceptual Models of Collie Basin Pit Lakes. Department of Water Project Report MiWER/Centre for Ecosystem Management Report 2010-12, Edith Cowan University, Perth, Australia. 95pp. Unpublished report to Department of Water. link

McCullough, C. D. & Van Etten, E. J. B. (2011). Ecological engineering of a novel lake district: new approaches for new landscapes. Mine Water and the Environment. 30: 313-319.link

Development of Pit Lake Beneficial End Uses

Clint McCullough (MiWER), Douglas Hunt (CUT), Louis Evans (CUT)

What planning and regulatory involvement if required to develop pit lakes into beneficial end uses?

Social licence to mine is encouraging much greater emphasis on sustainability and contribution to the local community of a post-mining landscape than ever before. Development of a pit lake resource into a beneficial end use depends upon input from the mining company involved, the local community and also relevant regulatory agencies. Planning must ideally occur before the first hole is dug, and from then on it should be regularly updated as economic and social climates change.


Photo: Wedge Pit lake in the Goldfields Region provides water for the nearby town of Laverton


Figure: Mine pit lakes relinquishment needs to be considered before beginning and during operational mine life

The most successful pit lake beneficial end uses have arisen when mining companies have engaged the desire and expectations of local communities in a supportive regularly environment to go beyond compliance; instead to leave a very positive mining legacy behind that they can be proud of.

Outputs

McCullough, C. D.; Hunt, D. & Evans, L. H. (2009). Sustainable development of open pit mines: creating beneficial end uses for pit lakes. In, Mine Pit Lakes: Characteristics, Predictive Modelling, and Sustainability. Castendyk, D. & Eary, T. (eds.) Society for Mining, Metallurgy & Exploration (SME), Kentucky, USA, 249-268pp.link

Opportunities for Sustainable Mining by Beneficial Pit Lake End Uses

Clint McCullough (MiWER), Mark Lund (MiWER)

Can Australian pit lakes be used for sustainable enduses for mining companies, communities or the environment?

Being a finite abstraction, “sustainable mining” is something of an oxymoron for what is inherently unsustainable activity. Nevertheless, in an era of increasing recognition of environmental and social damage through an ever-growing scale of mining coupled with increasing corporate social conscience for these activities, the mining industry usually works to reduce operational risk and retain its “social licence to mine” the community resource through a variety of strategies.


Figure: Conceptual beneficial end uses for pit lakes that have already been explored in Australia.


AMD in the Czech Republic; mine pit lakes and their waters are usually considered a liability

For best sustainable management of lease resources for companies, communities and the environment, pit lake management should be more than simply parochial meeting of regulatory criteria to lease relinquishment. Assessing current and potential end uses for pit lakes is an important, yet little-recognised way, in which significant benefits to all three of these stakeholder groups can be made over an indefinite long-period of time, and in a mutually beneficial fashion.

Outputs

McCullough, C. D. & Lund, M. A. (2006). Opportunities for sustainable mining pit lakes in Australia. Mine Water and the Environment. 25(4): 220-226.