PERMEABLE REACTIVE BARRIERS IN BIOPOLYMER SLURRY TRENCHES - PERFORMANCE STRENGTHS AND INSTALLATION WEAKNESSES

摘要

Permeable reactive barriers (PRBs) consist of a reactive media placed across a groundwater flow zone to treat dissolved compounds in situ. The reactive media is usually some form of granular iron, and the dissolved compounds are often chlorinated solvents. The advantages of PRBs are many, including the generation of small volumes of waste, enhanced protection of receptors, targeting of treatment to source zone flows, and reduced costs per treated mass. While treatment media installation has typically been done through either open excavation or injection, much excitement has been generated by the recent use of biopolymer slurry trenching to excavate deeper and with more certain placement of the treatment media. However, both the design and construction of PRBs in biopolymer slurry trenches must anticipate the full range of installation conditions, so that the very characteristics that maintain the excavation opening do not block the groundwater flow through the media. At a minimum, PRB failure causes incomplete treatment and false confidence. Of greater significance, a PRB failure may also create a redirection of the groundwater flow, changing the course or speed of a release, magnifying the exposure of contaminants to receptors.