December 18, 2014
Jeff Jolly (AQ2) was invited to chair the second day of presentations and discussion at The Water in Mining Summit, held in Perth 16-18 September 2014. He has provided a summary of the event.
Mining plays a major role in water use in WA (36% of all water is used by mining companies and 56% of all groundwater used is in mining) and interest in the Summit was good, with about 80 attendees from mining companies (BHPB, Newmont, Rio, Roy Hill, MMG, Anglogold Ashanti and Cameco), government departments (Department of Water WA, Department of Environment and Heritage Protection QLD, Bureau of Meteorology, CSIRO) and a number of consulting groups.
It was clear from the papers presented that water management in the WA mining industry is no longer a simple question of where to find a water supply or how to dewater. We now face the more complex issues of managing cumulative water impacts on downstream users of all kinds, especially groundwater dependant ecosystems. Observations on some of the key papers and themes follow.
Two keynote addresses were presented by government agencies (Paul Brown, DoW and Chris Loveday, DEHP) who gave an update on how Government departments are dealing with the changing mining and water environments. In WA, legislation is being consolidated and made simpler and DoW are encouraging a more consultative approach to project reviews, with Paul Brown emphasizing the need for companies to deal with the department from the very early stages of a project’s development. Chris Loveday explained how the floods in Queensland during 2008 and 2010/11, together with the growth in the coal seam gas (CSG) industry, have required the DEHP to adopt a more flexible approach to help companies improve water management. For example, the use of temporary emission licences (TELs) allowed the government to assist mines in managing the disposal of excess water after the major floods, without impacting on overall downstream water quality or changing overall licence conditions.
Speakers from BHPB and Newmont both spoke of the growing role strategic water management plays in their businesses. Rynhard Kok (Newmont) spoke on developing a global strategy for water management, while Peta Barnes (BHPB) discussed innovative solutions to manage groundwater quality and cumulative impacts. BHPB are assessing a new approach in their water management, moving away from merely complying with conditions in individual water use licences, to a broad catchment based approach of assessing and managing impacts on key environmental receptors. Based on pathways and risks to GDEs that could potentially be impacted, relevant levels of protection are emplaced. This catchment wide approach allows cumulative effect assessment and management. It is clear from the recent EPA statement on cumulative impacts, that regulators in WA are concerned about catchment wide cumulative impacts, but BHPB observed that the cumulative effect management is easier where they are the only mining group within a catchment. Rynhard explained the approach that Newmont has taken in implementing a global water management strategy. The global strategy is seen as the framework for local implementation. Similar to BHPB, a watershed management approach is one of their framework pillars, another being internal collaboration. The internal collaboration has seen water management teams being developed in each of their mines (where applicable) to work together across the numerous fields (engineering, geotech, environment, etc) to develop suitable management measures.
As the industry matures, concerns about the lakes that may form in abandoned pits will only grow. Phil Whittle (Hydrobiology) discussed closure planning linked to open pits, noting there were currently 97 pit lakes in the Pilbara and ~670 open pits which could become future pit lakes. He emphasised the need for advance planning for closure and the site-specific nature of most of the plans. The infilling of open pits is not always the solution. Any double handling or quarrying of waste clearly adds to the project’s cost; moreover, even DMP regulations may prevent backfilling where an abandoned mine still contains ore that has not been mined, only because of current market or technological constraints.
Jon Hall (RPS) presented a paper on the hydrological process related to pit lakes and the simple actions to manage these processes, providing practical closure outcomes. He emphasis simple solutions and a risk based approach to assessing the need for infilling of open pits. During discussions, Jeff Jolly also raised the concern that infilling changes open pits from groundwater sinks (where all contaminants generated around the mine are captured within the pit) to throughflow lakes, where contaminants can move offsite, impacting downstream users.
TSF Water Management
Frans Basson (Newmont) discussed different tailings disposal options (from slurry to dry cake) and the impacts on water requirements and water management. He emphasised the need for clear (sometimes simple) water balance models (continuously updated with actual data) and a tailings water management plan to allow ongoing water management.
David Jones (Bureau of Meteorology) presented some very interesting data on changes in the rainfall and temperature patterns in Australia, and expectations for ongoing changes into the future. It appears highly likely that the northern parts of the country, including the Pilbara, will be getting warmer and will have an increased rainfall, while the south-western parts of WA will become drier and hotter. Thus, the issue of managing seasonal surface water may be an increasing component of mining in the Pilbara.
Tim Bleby (Astron) provided some background on what GDEs are, how to assess whether plants are groundwater-dependant and how they might respond to changes in groundwater conditions. He emphasized the need for monitoring and provided examples of what kind of monitoring can be undertaken, not only of the vegetation, but also the associated environmental conditions (water levels, rainfall, etc). Tim’s take home message related to GDEs was:
- Choose the right tools to investigate GDES and obtain multiple lines of evidence
- Understand how plants respond to change
- Understand the linkages between plants, the unsaturated zone and groundwater and
- Develop a conceptual model of how the system functions.
Pilbara water resource assessments
Don McFarlane (CSIRO) presented the results from one example of the regional assessments of the hydrology of the different catchment areas in the Pilbara that CSIRO have recently completed. The CSIRO studies provide context for more detailed hydrological investigations and help put individual and combined impacts from resource development into a broader context of climate variability and change.
A number of papers were presented related to site-specific aspects of water management, especially the treatment of water. These included:
- James Zhan (Rio Tinto) – hydraulic modelling to improve the efficiencies in water supply systems for examples in the Pilbara
- Neil McIntyre (Queensland Uni) – managing water where supply and demand uncertainty exists
- Veronique Bonnelye (Degremont) – case study on treatment of AMD from a mine in Chile
- Richard Paterson (C3L Innovations) – innovative, commercial opportunities related to management of excess mine water, including agriculture.
- Gary Smith (URS) – case study on treatment of mine slurries from a mine in Indonesia
- Grant Douglas (CSIRO) – using hydrotalcites to treat AMD
- Russell Martin (Australian Groundwater Technologies) – using managed aquifer recharge (MAR) in the mining industry
- Duncan Howie (HDS Australia) – Wastewater treatment approaches at mine camps
Overall, it was clear that water management in the mining industry is no longer a simple question of where to find a water supply or how to dewater. We now face the more complex issues of managing cumulative water impacts on downstream users of all kinds, especially groundwater dependant ecosystems. In WA, the Government is keen to consult at the early stages of all water use aspects of new mining projects. The individual papers on site-specific water management show that in many cases, solving the larger scale issues requires the application of tried and tested solutions to the many smaller issues that contribute to the whole.