INNOVATION March-April 2014

f ea t u r e s

Sustainable Groundwater Management Strategies Remediating Metal Contamination Using Permeable Reactive Barriers

Michael Choi; Ben Lin, P.Eng.; and Gabriel Viehweger, P.Geo.

T remendously flexible, permeable reactive barriers (PRBs) are a sustainable biological and chemical treatment approach in which subsurface “walls” are installed to intercept and passively treat contaminants in groundwater, thereby reducing risks to the receiving environment and downstream receptors. Thanks to their flexible attributes and adaptation to site-specific conditions, PRBs are designed to treat a variety of inorganic and organic contaminants in groundwater through their destruction or adsorption. For instance, PRBs have been successfully applied to mitigate groundwater impacts from metal leaching and acid rock drainage (ML/ARD) in numerous sites across the US and Canada where groundwater has been adversely impacted by mining-related operations. PRBs intercept contaminated groundwater in situ using a reactive media, which then responds to or adsorbs contaminants such as copper, zinc, chromium, selenium and uranium as the groundwater flows under natural or induced gradients. Several installed PRBs have demonstrated typical metal removal rates greater than 99%. Different reactive materials can be used in PRBs to treat a wide variety of metal contaminants, as shown in the following table.

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