Characterization and monitoring of solid waste disposal sites using geophysical methods: Current applications and novel trends

Landfilling remains the most attractive waste management method for solid waste. Although not the most efficient and environmental-friendly option, landfills offer a cost-efficient solution compared to other alternatives. For any landfill to be successful site selection, construction, operation, and post-closure monitoring is critical. Synergistic use of geophysical methods and traditional point sampling (e.g., borehole sampling) allows for high resolution characterization and monitoring of landfills during all stages of operation; from guided site selection, to construction integrity and waste characterization, to leachate recirculation and leak monitoring. Geophysical methods offer advantages, such as high temporal and spatial resolution, non (or minimally) invasive and cost-efficient operation, rendering them a very powerful tool for characterization, and long-term monitoring of waste disposal sites. Since geophysical methods involve the indirect imaging of the subsurface cautious implementation, including direct sampling, is needed for successful application. Multiple geophysical methods have been shown to be suitable for landfill characterization and monitoring. Electrical (resistivity, induced polarization, and self potential) and electromagnetic (transient electromagnetic methods, ground penetrating) are the common geophysical methods employed in waste management operations due to the increased conductivity of waste and leachate. Seismic methodologies can also be used to describe subsurface geology and possible waste horizons. In certain cases, magnetic measurements can also be used for the monitoring and characterization of landfills. Typically, geophysical methods are used to: • spatially delineate landfills and define landfill geometry, • monitor and characterize the spatial distribution of moisture, gas content, and leachate inside landfills, • identify classes of buried waste based on material composition, • monitor the integrity of the liner, and • identify and monitor leachate leaks, and the associated contamination plumes. With this chapter we aim to introduce common geophysical methods and provide examples for application in landfills. For the geophysical methods of interest the basics principles, along with up to date references are provided, and the advantages and limitations for waste management operations are discussed.