imaGeau’s Subsurface Monitoring Device (SMD): Dynamic monitoring of underground pollutants imaGeau’s SMD allow the monitoring in real time and in situ of varying pollutant levels in an aquifer. The method used is based on the detection of an insulating fluid (NAPL) in a conducting formation using the electrical method. This process has already been in use for decades in the oil exploration field. imaGeau’s SMD enables a dynamic monitoring of the LNAPL/water interface (Light NAPL such as hydrocarbon) on the surface of the water table or of the water/DNAPL interface (Dense NAPL such as halogenated solvents) on the top of the substratum. Using an electrical investigation method, imaGeau’s SMD measure the level of resistivity in the formation and more particularly its degree of saturation. The latter can vary greatly when very resistive NAPLs have taken a space formerly filled by water in a porous area. As shown below, the SMD have been designed to measure underground water conductivity in situ. Thanks to numerous captors (200 max) this conductivity can be monitored across the whole width of the aquifer. This is in contrast with the piezometric method that does not differentiate the various fluids mixed in the borehole. Electric and saturation data is logged and transmitted to user for analysis. Through this underground monitoring – in real time and at high frequency – the imaGeau technology contributes to reducing the cost of cleaning operations after pollution on industrial sites: A / Before pollution : « alert/early warning » mode: è detection of the source of pollution è immediate intervention B / Post pollution: « monitoring the impact of cleaning operations » mode: è accurate description of the time and space movements of the various pollutants; è quick response in the focus of the cleaning operations; è improved knowledge of the extraction process. This continuous monitoring is possible even while keeping human intervention and movements to a minimum. NB: Should NAPLs be detected in a sandy clay soil saturated in fresh water, the observatory can detect a change in the level of saturation as low as 0.8% that is 8ml of NAPL per litre of underground water. imaGeau is an innovative start up company created in partnership with the French National Centre for Scientific Research (CNRS) in 2008. Its focus is to develop new technologies in the aquifermonitoring field. The imaGeau SMD is patented in France and Europe (2008).