Acid Mine Runoff

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Acid mine drainage (AMD), sometimes called acid and metalliferous drainage, occurs when acidic water is released into the environment from active or abandoned mine sites. This lowers the pH and may introduce toxins like heavy metals into the downstream watershed. Monitoring in and around mine sites can help to detect, track the efficacy of mitigating measures, and even prevent AMD by giving advance notice of changing conditions.

Acid Mine Drainage Measurements

Tailings are the waste product from mining operations which often contain sulfide minerals. Oxidation of these minerals acidifies the water of tailings dams and may increase the amount of dissolved metals. Unmitigated outflow of such waters into streams and rivers can have dramatic effects.
Toxic pH levels sometimes as low as 2-4 can cause aquatic life to perish or abandon affected areas, thereby reducing biodiversity.
Heavy metals accumulate in aquatic species and contaminate waters used as drinking water sources.
Abandoned mine sites are particularly problematic since nobody claims responsibility and implements measures to reduce drainage in many cases.
Untreated waters from abandoned sites may continue to be released over long periods of time, leading to the accumulation of toxins over a wide area.
Some rock and soil types naturally contain sulfide minerals which can affect streams and rivers similarly in what is known as acid rock.
Highway construction, building excavations and other earthworks can trigger ARD by disturbing sulfide-rich rock and soil formations.
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Typical Acid Mine Drainage System

Acid mine drainage has the potential to drastically alter downstream waterways. In some cases, this is even visible by changing the color of the water to red or orange hues. However, in many cases, the occurrence and effects of AMD can only be detected in real-time by automated sensor systems. Automated monitoring of factors like rainfall, water levels, pH and conductivity provides both notice of acute events and tracking of long-term water quality changes.

NexSens acid mine drainage monitoring systems typically utilize several sensor types. Rainfall data can be collected with tipping bucket rain gauges, and water level in sources like tailings dams and downstream streams and rivers can be measured with pressure transducers or non-contact level sensors. Various water quality parameters are measured with multisensor sondes such as those from YSI, Hydrolab, Eureka and In-situ. Conductivity and pH are two important water quality factors, but these can additionally measure temperature, dissolved oxygen, turbidity and many other parameters.

Mast-mounted X2 data logger systems record measurements from the various sensors and transmit data wirelessly in near real-time via radio, cellular or satellite communications to the WQData LIVE web datacenter. WQData LIVE has a suite of data management tools and alerts to changing conditions via email or SMS text message.

Water quality sensors are often installed in a perforated deployment pipe securely mounted on the banks of ponds, rivers or streams. Sensors may be secured at a fixed position within the pipe and easily removed from the water for maintenance and calibration. Multiple sensor ports on the X2 logger accommodate situations where several sensors will be mounted at one location.

Contact a NexSens Applications Engineer today to discuss your acid mine drainage monitoring application.

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