Mining activity occurs throughout much of Canada (Figure 15). The metals and minerals sector is largely made up of gold, copper, lead, zinc, iron ore, coal, asbestos, nickel, potash, titanium, aluminum, platinum, diamonds, and uranium.* The NRTEE?s study of water use by the mining sector considered mining and mineral processing at the mine site for metallic and non-metallic mining operations. The description of water use and issues generally apply to hard rock mining (metal mining), soft rock mining (coal), uranium mining, and potash mining.
The mining sector is not a significant user or consumer of water and the mining sector does not see water availability as a major constraint or risk to operations in the future. However, as mines have the potential to significantly impact water quality and surrounding ecosystems, water quality is one of the most important management considerations.
The mining sector is not a significant user or consumer of water, however mining activities can impact water quality and ecosystems if not managed properly.
Climate change impacts may have important consequences for the management and future design of mines across Canada, particularly in the North.
Key issues facing the mining sector include:
- Water management and quality
- Climate change adaptation
The mining industry is an important contributor to Canada?s economy. In 2008 the industry contributed $40 billion to Canada?s GDP which included $9 billion in mineral extraction and $31 billion in mineral processing and manufacturing. Internationally, Canada is one of the world?s leading mining countries and ranks among the largest producers of minerals and metals. The industry accounted for 19% of annual Canadian goods exports in 2008.
Over the long term the mining sector is expected to see modest growth, varying among the subsectors of coal, metals, non-metallic minerals, and mineral fuels. The medium-term projections see improvements largely due to the unprecedented amount of fiscal and monetary stimulus injected into the global economy. Long-term growth is expected for uranium production, diamond production, and potash. On the other hand, coal mining is predicted to have negative growth over the medium and longer terms, notably due to the anticipated shift to cleaner energy producing technologies.
Mining activities can affect water resources during all phases of mining: exploration, planning, development and commissioning, operations, and closure. Important water considerations for a mine site include management of stormwater, mine water, and groundwater inflow; process water (includes recycled and make-up water); tailings pond overflow; and contact water. Water is used or managed in most aspects of the mining life cycle (Table 7). Mine development and Commissioning, Operations and Closure are the most important phases with respect to water resources.
Mine construction may alter both surface and groundwater flows due to development of access corridors (roads), mine site facilities, and discharges from the mine site into the streams/rivers.
The greatest potential for long-term impact to surface water and groundwater flows occur within the local watersheds and to river systems downstream from the mining operation. All water that comes into contact with ore or waste rock requires some treatment before discharge; the risk is higher with sulphide ore mines. All mining activities, such as site preparation, mining of ore and waste rock, mineral processing, tailings management and transport of mineral products, use water but at different levels of intensity (m/tonne of ore).
In most types of mining, relatively little water is used in actual ore excavation/production. Its principal use is for drilling and dust control. A notable exception is potash solution mining found in Saskatchewan.
Most mines process the minerals on site. The mined particle size from typical hard rock mines measures several centimetres up to a metre, thus requiring reduction of particle size so that minerals can be separated from waste and recovered in downstream processing. During particle size reduction in grinding mills, water is added and further mineral recovery is carried out in the aqueous medium. Water is also used for dust control. After the mineral recovery processes the waste (tailings) is usually transported through a pipeline as an aqueous slurry to the tailings storage facility where the solid fraction settles out and as much water as possible is recycled to the processing plant for use as process water.
To the extent possible, mining operations maximize recycling of water in order to minimize both their freshwater make-up requirements from either surface or groundwater sources and water treatment requirements. This is accomplished within constraints imposed by water quality requirements, water availability, and discharge considerations. Surplus water collected from the mine area is discharged (and treated first if necessary) if it is not needed to operate the mine and associated mineral processing systems. During the closure phase, water management is important to ensure no negative long-term impacts result from water coming into contact with potentially acid-generating ore and waste material.
The primary water issue facing the mining industry is the management of water whose quality has been adversely affected by mining operations and the potential release of these waters back into the environment. The key issues for a mine are two-fold: water management and climate change adaptation.
For most mining operations in Canada, the key issue is too much water rather than a scarcity of it (with exception of the Prairies and the North). Therefore, water management and particularly the segregation of clean and ?contact? water by upstream diversion of clean runoff is one of the most important issues from an operational perspective.
The ?site water balance? is an important tool for water management in mining operations, and refers to the need to account for all water in and out of the site. The challenges of a site water balance include extreme events (the result often being large volumes of water entering the mine site), annual snow melt, and the mine site location, requiring the companies to deal with the associated site hydrology.
While the mining sector?s consumptive water use is relatively small, a mine?s water management can have a significant effect on a region?s water quality if contaminated water is released to the surrounding environment (via surface water runoff or wastewater discharge). This in turn can affect downstream water users and the health of the ecosystem. One significant issue related to water and mining is the use of natural lakes for tailings impoundment areas,* an option that is considered by some mines in Canada but rarely allowed by federal regulators.
Water treatment is costly so mines make great efforts to manage the water footprint of a site to both reduce costs of water treatment and to minimize impacts to downstream water quality. As part of this effort, mines segregate clean and used waters in order to reduce the volume of water to be treated.
Important climate change effects relevant for mining operations include changes in the amount of precipitation, changes in the timing of precipitation, and an increase in the frequency of extreme events. As the NRTEE?s True North report on adapting infrastructure to climate change in Northern Canada found, melting permafrost will have a serious impact on the stability of engineered structures.102 This will affect the design of future tailings impoundment facilities to avoid the failure of tailings impoundment dykes, which could result in a release of tailings and impact the environment. In light of potential increased precipitation volatility this issue may become more prevalent in future mining operations. Having a robust and adaptive water management plan will help prepare industry for this uncertainty.
A recent study found that (1) while the effects of climate change are not well understood, the majority of mining operations will be affected by climatic hazards including vulnerabilities in the closure phase, and (2) climate change is a minor concern in this sector and there is limited adaptation planning occurring.103 However, a number of recent initiatives and/or reports take climate change into consideration for mining practices and guidelines.?
The main driver for improving water efficiency by the mining sector is energy costs associated largely with water treatment. A secondary driver for improvement comes from the pressure put on the industry to improve its overall environmental management practices as water quality from mine sites can have a significant impact on the surrounding aquatic ecosystems. There appear to be opportunities for further improvements in water efficiencies in the mine processing phase. Many companies are working toward this goal and identifying corporate targets for improved water efficiency. Some companies are participating in the Global Reporting Initiative. On the whole, the industry is trying to improve upon its sustainable practices and gain greater social licence to operate.
Water availability in Canada is not likely a factor that will limit the sustainability of the mining sector because the sector is not a significant water user. The most important issue facing the mining sector is its potential impacts on the watersheds within which the mines are located. Water quality is, and will continue to be, one of the most critical components of the industry?s operational and strategic goals. While not a significant user of water on a consumptive basis, the sector is very aware of the amount it does use and continues to strive for improved use through both voluntary means and regulatory requirements. Past experience in this sector has shown that there are benefits to be had in pursuing best management practices and innovative solutions.
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* Aggregate mines (e.g., sand and gravel) were not considered in this report.
* Information on the economic state of the mining sector was taken from ?A Report on the State of the Canadian Mining Industry. Facts and Figures 2009.? The Mining Association of Canada. Accessed from http://www.mining.ca/www/media_lib/MAC_Documents/Publications/2009/2009_F_ and_F_English.pdf.
* The use of freshwater lakes in Canada for tailings impoundment areas is allowed under regulation of the federal Fisheries Act.
? Environment Canada?s 2009 Environmental Code of Practice for Metal Mines; the Canadian Dam Association?s Dam Safety Guidelines; the Mining Association of Canada?s Guide to the Management of Tailings Facilities.