July 21, 2016
Dan Twitchel, Senior Environmental Specialist at Barrick’s Turquoise Ridge Joint Venture in northern Nevada, checks water quality at a local creek near the mine
Have you ever wondered what the chemical composition of your water is? Claudio Andrade has. Andrade, Barrick’s Manager of Environmental Chemistry, advises Barrick operations all over the world on matters related to water monitoring and geochemistry, the study of the composition of the earth’s materials and their interaction with water.
Andrade helps the company interpret baseline water measurements and environmental conditions around prospective mine sites before a mine is ever built. He also helps develop water-monitoring programs so that mine operators can gauge the impact that their mine is having on the local environment.
Water samples collected at and around a mine site are sent off for analysis by independent third parties to ensure impartiality and transparency.
Water monitoring describes activities carried out to ascertain the quality and quantity of water in a given water system. These activities can be carried out by mining companies, independent contractors, as well as governments and nongovernmental organizations. In the case of a prospective mine, water monitoring begins during an environmental and social impact assessment, a multi-year study undertaken by a mining company to identify a mine’s potential social and environmental impacts—both positive and negative—on the local environment and community. Large volumes of data, including water flow rates, water quality, sediment composition, and aquatic life characterization, are gathered as part of a baseline measurement that factors in natural seasonal variability.
"At the end of the day, water is the chemical signature that expresses conditions in the area, whether natural or man-made," Andrade says. "The baseline is really the snapshot of those conditions before we got there."
An environmental technician gathers data from a water-monitoring station near Las Taguas River, close to Barrick’s Veladero mine in Argentina
Water quality
Many factors affect water quality, but soil and geology in a given area are the primary sources of a water system’s chemical signature, Andrade says.
For example, if a river runs through an area with high levels of naturally occurring salts, the river water will have higher salt concentrations. If the water levels decrease in the river due to drought, this results in the concentration of those naturally occurring salts, much in the same way reducing a sauce in cooking would concentrate the taste of certain flavors and spices. In other words, chemical elements can become naturally concentrated with or without mining activity in a given area.
Soil and geology in a given area are the primary sources of a water system’s chemical signature.
Even so, a mine operator must explain how it will mitigate potential mine impacts as part of the environmental impact assessment. At this stage, an operator would need to determine how the mine would treat water, how it would recycle water and how it would divert water around the site, among other mitigating activities.
The operator must also determine a schedule to sample different water types, such as water that comes into contact with excavated materials or post-processed materials at a mine site and non-contact water that flows around the site. When complete, the assessment is submitted for regulatory review, which typically lasts six months to a year. If the assessment is approved, an environmental permit is issued. The permit outlines environmental commitments and actions that a mine must take, including water monitoring requirements.
How monitoring works
Water sampling can be done manually for a comprehensive suite of water quality parameters or via automated monitoring stations that check for general water quality characteristics such as electrical conductivity, acidity levels and flow rates.
When a mine is in development, water sampling is typically conducted monthly, if not more frequently, depending on the natural complexity of the local water system. Once a mine is operating, sampling may occur daily, weekly or monthly in various locations around a mine site, depending on operational or regulatory requirements. "The environmental and social impact assessment sets out regulatory commitments, but for operational or scientific reasons, we sometimes expand the variables that we’re monitoring in the water to understand geochemical processes better," Andrade says. "We may also volunteer to monitor an area if the community benefits from it or asks us to participate in the monitoring activity."
Treatment and monitoring continues for years after a mine is closed.
Water samples collected at and around the site are sent off for analysis by independent third parties to ensure impartiality and transparency. These labs use specialized equipment to measure parameters such as the concentrations of various metals using international standardized methods. This monitoring data then undergoes quality assurance and quality check processes, is stored in controlled databases, compiled, analyzed and interpreted. In addition, monitoring results are compared regularly against baseline data or regulatory thresholds to ensure a mine is in compliance.
"This is a transparent process," Andrade says. "Once this data is submitted to the government, it’s publicly available."
Regulators conduct inspections of mines to ensure that these sites are in compliance with their permits. During these inspections, the site environmental team may take water samples alongside the regulator as part of the due diligence process. During operations, companies must continue to monitor water quality and quantity, and, if needed, treat water that comes into contact with potentially acid-generating rocks. This treatment and monitoring continues after a mine is closed for years to ensure that the environment around the closure site is not impacted.
"Compliance is a priority and our water quality monitoring programs are integral to maintaining this commitment," Andrade says.