Field: Damage-reducing technique, Soil characterization
Global Technical function: Managing
Technical Function Unit: Modelling, Software tool

SoilCAM - Geophysical software

The SoilCAM (Soil Contamination: Advanced integrated characterization and time-lapse Monitoring) project is a four-year initiative funded by the Seventh Framework Programme, FP7, a grant funding programme, which will end during 2012. It aims to develop integrated strategies and
damage-reducing techniques to detect temporal and spatial change of chemical and physical properties of the subsoil that can be related to sustainable environmental recovery of polluted sites.

A number of geophysical tools such as the Polares instrument have been developed within the project to study pollution in groundwater and soil and to collect relevant hydrogeological data from specific sites. These instruments generate large amounts of geophysical data for
soil characterization in different types of datasets. Thus, new software and strategies are needed for managing this data.

Based on these needs, a new geophysical software code for modelling and inversion of complex conductivity electrical data has been developed within the framework of the project. It is based on solving the tomographic problem of creating relevant images of the studied sites. The results are 2D or 3D images (depends on the collected data set) of the soil conductivity and polarizability. The new software tool interprets the dataset of soil electrical conductivity and polarizability through a strategy called joint inversion, allowing it to process data from different frequencies simultaneously. The code uses adaptive meshes which are refined close to the electrodes. The inversion schemes are based on a Primal Dual - Interior Point: the approach gives a great flexibility to the user to adopt the best algorithm, allowing a sharper or smoother reconstruction of the tomographic images. The specific conditions of the site to be imaged determine the choice of algorithm. Processing of conductivity data offers the opportunity to adapt the mesh in regards of resolution. The overall approach is implemented in a software package based on the NES-GeoElectric library, allowing reconstruction of 2D and 3D electrical data optimized for speed and for parallel operation on multi-core computing architectures. The intention is to release the software package under a public domain license in the beginning of 2013. The code has been used in a number of test sites in Italy to interpret both data collected from the surface both in cross-hole configuration.  Thus, the technology readiness level of the software is reaching a 9 on the TRL scale.

Some new and innovative strategies have also been developed within the framework of the project. One example, mentioned above, is the new strategy for joint inversion of geophysical data with the capacity to integrate different geophysical datasets in a unique inversion process; this minimises the ambiguities due inherent to inversion procedure of geophysical data and provide more reliable geological and hydrogeological models of the subsoil. For instance, different sets of electrical data and electromagnetical data can both be integrated into a model, to achieve more robust models of the subsoil in terms of hydrogeological behaviour: i.e. improved models that can be used to constraints the numeric or analytical model of groundwater flow and transport of contaminants. Also, there is a new strategy of solving the inversion problem of tomographic dataset based on the staggered grid approach which offers a more flexible interpretation of data, to minimize some differences and include interpretation uncertainties in the results through statistical strategies.