Construction and Performance Monitoring of In Situ Reactive Barriers

In situ reactive barriers have been constructed by a variety of means and with a range of reactive materials. Zero valent iron reactive permeable barriers have been installed to remediate chlorinated solvent contaminated groundwater by abiotic degradation of the halogenated volatile organic compounds into harmless daughter products. Alternative reactive materials are used for precipitation, sorption or biodegradation of various groundwater contaminants. The conventional means of installing such reactive barriers in a funnel and gate configuration is by braced gate excavation, and for continuous permeable barriers by slurry wall, augering, trenching, jet grouting and hydraulic fracturing techniques. This paper addresses those monitoring activities necessary to ensure a reactive barrier is constructed as envisaged, and that the barrier performs as designed. Construction monitoring activities involve quantifying barrier geometry and in situ properties, and impact of the barrier on the surrounding groundwater flow regimes. Performance monitoring activities involve groundwater chemistry data, up and down gradient of the barrier, tracer and hydrogeological tests, and field sampling and analysis of barrier in situ materials. Field case studies are used to elaborate on what monitoring activities are essential for performance monitoring of reactive barriers.