5.2.2 Water

Water management is a critical long-term issue for the mining industry for a number of reasons:

  • Water is an important vector for the potential spread of pollution (whether as a result of an immediate incident or the gradual build-up and movement of contaminants over time), making it a critical compliance issue as well as being a risk to the environment and human health if not responsibly managed
  • Mining can require large volumes of water and often takes place in locations that are already waterstressed
  • Poor water management can have significant social and political consequences, where local communities are affected by, for example, water scarcity, high levels of agricultural activity and a lack of sufficient water infrastructure

In this context, Gold Fields remains committed to responsible water stewardship, which enables shared benefits for our stakeholders and security of supply for our operations. Key enabling factors to achieve effective water stewardship include publicly reporting our water usage and material water risks and engaging pro-actively with affected stakeholders.

In addition, Gold Fields adopts a catchment-based water management approach. This means understanding the social, cultural, economic and environmental value of water at the catchment scale to identify material water stewardship risks and provide context for operational water management. At an operational level our mines are tasked with managing operational water inputs (both qualitatively and quantitatively) and maximising resource sustainability to achieve operational flexibility and cost savings.

Water withdrawal across the Group increased sharply to 35,247 Mℓ (2014: 30,207 Mℓ), and water withdrawal per ounce produced was up from 13.16 kℓ in 2014 to 15.77 kℓ in 2015. The main reasons for the increased water withdrawal were:

  • Higher usage at South Deep due to the start-up of the water-intensive re-mining process and less water available from the return dams due to the dry summer period
  • Increased water withdrawal at St Ives due to opening up of the Invincible, Neptune and A5 ore bodies
  • Higher levels of dewatering from the Waroonga pit at Agnew as mining at the operation is progressing deeper and into new areas. Furthermore, the dry hot summer of 2015 increased evaporation rates from the processing circuit
  • Water abstraction at Granny Smith by an outside company

Though more water was drawn into the system, water recycled and re-used improved by 1.64% during 2015.

Water resource management
Each operation implements an Environmental Management System (EMS), through which it assesses, manages, monitors and reports on water use and quality – including discharges, where these occur.

All of Gold Fields' operations are required to have an operational and predictive water balance in place. The water balance is a fundamental tool for understanding current and future water management requirements. Water balances enable decision-making regarding the current and future security of our water supply, as well as other operational and social concerns, such as modelling storm events to determine the impact on dam water levels and the potential risk of unplanned discharges.

Whether mines are water-positive, water-balanced or water-negative depends on a number of dynamic variables. These include climatic variables such as seasonal rainfall and evaporation rates, the volume of water entering underground workings or open pits (e.g. via aquifers and surface run-off respectively) and the type of processing employed (e.g. heap leach or Carbon-in-Leach processing).

Gold Fields applies the following measures to manage the water balance at its mines and to promote water stewardship:

  • Regional application of the Group water management guideline (a summary is available online at www.goldfields.com/sus_guide. php) – including the development and implementation of water management action plans
  • Implementation of physical measures to manage stormwater run-off – and keep clean water and mine water separate
  • Maintenance of water containment capacity (including the containment of inflow surges)
  • Water treatment – including reverse osmosis plants
  • Promote water reuse and recycling and conservation initiatives Group-wide
Group primary water withdrawal per ounce of gold produced
(kℓ/oz)		   Group water withdrawal
(Mℓ)
Group primary water withdrawal per ounce of gold produced   Group water withdrawal
Group water recycled/reused
(Mℓ)		    
Group water recycled/reused    


Water re-use, recycling and conservation
EIdentifying opportunities to enhance water re-use, recycling and conservation practices at all of Gold Fields operations was a Group balanced scorecard objective for 2015 and beyond. Enhancement of these practices can deliver multiple benefits, including cost savings, reduced impact in water scarce areas, improved regulatory compliance, identification and mitigation of water-related risks, reduction of mine closure liabilities and enhancing Gold Fields’ social licence to operate.

Across the Group, 20 initiatives have been identified, of which 16 will be implemented during 2016. The remaining four initiatives require further studies. Some of the most high-profile initiatives include:

  • Use of in-pit tailings storage at our Tarkwa mine instead of building new above-ground tailings storage facilities (TSFs). In-pit tailings storage has a higher potential for recycling and re-use of water than conventional tailings facilities as there is less evaporation and the tailings density is greater. In addition, the capital costs are likely to be less in terms of both construction and associated community relocation costs. In-pit tailings disposal has been in use at our operations in Australia and recently regulatory approval has been received for in-pit tailings disposal at St Ives
  • Treatment of nitrates in the pit water at Damang mine, using floating mats of plants that absorb the nitrates as nutrients
  • Development of a post-closure water management plan at South Deep, taking into consideration our surrounding mines, whose underground water may enter the mine’s underground workings, after they have closed
  • Replacement of the two low-volume underdrainage capture ponds with pumping wells at Cerro Corona, which are more efficient in capturing potential seepage from the TSF
  • Upgrading (where necessary) of all operational water balances to ensure they have dynamic and predictive capabilities by the end of 2016. This is also a Group balanced scorecard objective

Acid mine drainage
Gold Fields implements a range of measures to prevent or contain Acid Drainage (AD)1 at its operations and takes effective remedial action where incidents are identified. There were no material cases of AD reported in 2015.

Nonetheless, in the context of broader historical AD legacy issues in the Gauteng area, South Deep has taken a proactive approach to long-term AD management through its comprehensive water management plan. This involves ongoing water monitoring, containment of any AD generation on the old tailings facilities and water-treatment solutions that purify surplus fissure and process water to a potable standard.

In 2015, additional technical studies were initiated as a solution for managing potential AD generation in the underground workings postclosure. Underground AD generation is well managed during the operational phase by ongoing pumping to the surface of the underground water.

Other key water management initiatives implemented in 2015 at South Deep include:

  • Plume mitigation measures have been piloted at the Doornpoort TSF and groundwater extraction wells at the old TSFs
  • Further revegetation of the mine’s two historic TSFs, which has further reduced the generation of wind-blown dust to well below the legislated airborne dust level limits
  • The removal of the old South Shaft waste rock dump, which was a potential source of AD and other contamination, is almost complete. Rehabilitation of the footprint area commenced in 2015

Cerro Corona’s tailings and waste rock facilities were designed to avoid and mitigate the risks of AD. In addition, the mines closure plan contains various strategies, which are updated at least every two years as new technical information becomes available. A more detailed post-closure water management plan will be developed during 2016 to add to the existing body of technical work.

AD issues have also been identified at the Damang mine, however these are confined to one pit. Additional technical studies have been commissioned in 2016 to better manage the AD at mine closure.

Although Gold Fields has commissioned various technical studies to identify the steps required to prevent or mitigate the potentially material AD impacts at its Cerro Corona and South Deep operations, none of these studies has allowed Gold Fields to generate a reliable estimate of the total potential impact on the Group.

Immaterial levels of AD have been identified at the Tarkwa and St Ives mines

1 AMD or acid rock drainage (ARD), collectively called acid drainage (AD) is formed when certain sulphide minerals in rocks are exposed to oxidising conditions, such as the presence of oxygen, combined with water. AD can occur under natural conditions or as a result of the sulphide minerals that are encountered and exposed to oxidation during mining or during storage in waste rock dumps, ore stockpiles or tailings dams. The acidic water that forms, usually contains iron and other metals if they are contained in the host rock

Regional water initiatives

Americas region
Water security poses a significant long-term challenge at Cerro Corona as the mine operates in a national context of poorly developed water infrastructure, water quality degradation and serious water-related activism at both a local and regional level. Although Cerro Corona has not as yet been materially affected by such activism – this has had a serious impact on other operators in the Cajamarca region. As such, Cerro Corona has proactively implemented a range of responsible water management initiatives, including:

  • Rainwater storage and reuse: Rainwater is stored at Cerro Corona’s TSF within a closed-circuit water system, treated and reused by the operation. This enhances the mine’s water supply, while minimising both the amount of water discharged and the amount of local groundwater abstracted
  • Community water supplies: Cerro Corona has committed to providing local communities with additional, potable water during the dry season and has completed a number of projects focused on water provision to nearby communities as well as improving existing municipal water systems (p119)
  • Water monitoring: Cerro Corona works closely with community-elected representatives to monitor water quality and quantity at the Las Tomas spring and authorised discharge points around the operation

Such approaches have – in combination with effective community engagement practices and the generation of shared local value – played a key role in protecting Cerro Corona from the kinds of social tensions affecting other nearby mining operations.

Australia region
Water security poses a potentially significant challenge for the region’s mines – all of which are based in arid areas of Western Australia. During 2015, Gold Fields Australia proactively ensured that existing supply agreements have been extended to all its operations. This work will continue into 2016.

At St Ives, legal proceedings were commenced in 2014 against Nickel West, operated by BHP Billiton, relating to the continued supply of potable water to the St Ives operations. In early 2015, agreement was reached to settle all outstanding disputes. St Ives has also entered into secondary water supply agreements with other parties (including the Western Australian Water Corporation) to meet its ongoing requirements.

South Africa region
Water management is a sensitive public issue in South Africa, particular in the Gauteng area (where South Deep is situated), which suffers from the historical environmental legacy of more than a century of intensive, deep-level gold mining. This legacy means that there are high levels of AD in and around Johannesburg – most of it caused by now-defunct companies and operations.

Whilst not contributing to local AD, there are concerns that South Deep’s long life will mean that the mine is the ‘last man standing’ as Gauteng’s AD issues become more acute and social and regulatory pressure to act on the issue grows.

South Africa currently finds itself in a drought cycle that is one of the worst in 40 years and which, some experts indicate, could continue for between three to five years. The implementation of water re-use, recycling and conservation practices is therefore particularly critical at the mine.

South Deep compiled a risk-based water scarcity management plan in Q4 2015, which evaluates the key drought related risks and proposes a variety of solutions to ensure that the mine continues to obtain a secure supply of water for its employees and production purposes, while minimising the impact of its water use on the environment and other water users in the catchment. In the short-term these measures include:

  • Considering options to obtain water supplies from neighbouring mines
  • Further improving storage and distribution of recycled water within the South Deep water system
  • Investigating the potential of withdrawing underground water from old workings behind South Deep plugs, that minimise the inflows of water from interconnected mines

The drought has also had an adverse impact on the three reverse osmosis (RO) plants installed at South Deep over the past two years to treat process water and reduce the intake of Rand Water supply. The plants have not been operational since October 2015, due to water shortages.

Before the stoppage, the three plants had treated about 2 – 4 Mℓ/day, thereby of processed water thereby cutting the mine’s water purchase costs by an estimated R120,000 to R150,000/month. The RO plants also have the benefit of increasing the overall supply of water for other local users as well as reducing the overall amount of water in the mine’s system and the risk of dam overflows during periods of heavy rains. South Deep is currently engaging neighbouring mines to secure more process water to reactivate the RO plants and reduce intake from the regional water utility.

In 2015, South Deep completed the first phase of its stormwater management plan. This included the construction of concrete channels to separate clean stormwater in the surrounding catchment from water running off the backfill plant area and surrounding areas. This has helped to minimise the risk of unplanned, off-footprint water discharges from the old return water dams during the rainy season due to the diversion of clean stormwater away from the dams. The next phase of the project – the upgrade and lining of the return water dam at the old TSFs – is scheduled to commence in 2017.

South Deep has signed a memorandum of understanding with a US-based technology company to pilot an in-line continuous water monitoring system in 2016 that can provide real-time data on heavy metals and other contaminants. The technology will allow for significantly enhanced response times to any water quality related issues, through an early warning detection system.

West Africa region
Gold Fields’ Ghanaian operations – and Tarkwa in particular – face some challenges on water management, including intense periods of precipitation, particularly during southern Ghana’s two rainy seasons, and the significant footprint of the Tarkwa mine, meaning that there is a large watershed to manage.

This footprint includes the extensive surface area of Tarkwa’s North and South Heap Leach facilities. While both facilities were closed in 2014, a significant amount of interaction continues to take place between rainwater and the stacked ore. During 2015, stored contaminated water was being recycled on the South Heap Leach pads temporarily to improve water quality, through the absorption of ions by the vegetative cover (plants) on the heaps.

A second response by the mine was the construction of pipes and the transportation of contaminated water from the South ponds to the North Reverse RO plant, since the South RO plant had been decommissioned to save costs. The rinsing of the North heaps with process water continued. Excess water from the North heaps is treated at the North RO plant and discharged.

The operation of the RO plant, which was established at the behest of Ghana’s Environmental Protection Agency, produces concentrated brine, which is being temporarily stored on site in the TSFs. As part of the investigation into the permanent elimination of brine through plant absorption, a 13 hectare test plot of rubber trees (one of the major tree species cultivated in the region) was established at the North Heap Leach facility in Q4 2015, and is being irrigated with brine. This will be monitored in terms of its suitability as a long-term solution for brine management.

In late 2014, Tarkwa submitted its long term decommissioning plan of the North and South heap leach facilities to the regulator (EPA). Subsequent to the submission, the regulator requested technical studies on the end use of the heaps. These studies were completed in 2015 and submitted to the EPA. We are awaiting a formal response.