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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).