Exploitable results Data processing, calibration, performance evaluation The definition of the most appropriate methods to integrate and calibrate geophysical investigations is essential to obtain a valid and cost effective procedure for the assessment of contaminated sites. Compared to conventional methodologies, an assessment approach based on a limited number of invasive investigations (sampling, boreholes, etc.) plus an extensive use of combined non invasive geophysical surveys is very promising for the reduction of the assessment costs and for the production of more detailed assessment reports. The definition of the performances, limits, applicability conditions and costs of these techniques is also essential to prevent the inappropriate use of geophysical methods and to help the end-users in optimising the decisions related with the financial support of the investigation activities. The result consists of a methodology for calibration and integration of geophysical techniques applicable to brownfield assessment and for cost-effective combination of geophysical techniques with conventional methods. The methodology defines the most convenient approach for deriving from geophysical data qualitative and quantitative indications useful for the assessment of the condition and the contamination of a brownfield. The description of the optimal calibration procedures is organized according to a synthetic template. A calibration template is defined for each geophysical measurement in application to each specific objective where the method can give a positive contribution. Laboratory measurements and field measurements Complete geophysical datasets in some brownfields and polluted sites, laboratory and controlled field measurements have been aimed to: 1) evaluate the time and performances of different geophysical methods 2) create database of physical, geochemical and sedimentological properties of samples from brownfields and contaminated sites and 3) improve the implementation of scaled realistic subsurface models to be used at the test tank facility and in the numerical simulation of geophysical response for data calibration and survey procedure improvement. The selection of the test sites was performed in cooperation with the end-user partners in order to identify situations that are representative of classes of broad and urgent interest in the field of brownfield rehabilitation. Interaction between numerical simulation, laboratory and controlled field measurements were the core activity towards the development of effective procedures for the extraction of quantitative information from non-invasive records and the reconstruction of reliable subsurface models. Sandbox tests were performed to provide datasets and subsurface models for development in the field of processing, modelling and inversion. The subsurface models implemented to date and exploited for data acquisition included PVC and metal pipes, fully or partially filled by different types of liquids (hydrocarbons, water, water contaminated by organic and inorganic compounds) fully or partially filled by different types of liquids (hydrocarbons, water, water contaminated by organic and inorganic compounds) and steel balls or clay blocks. Water was injected and drained by the bottom of the box to simulate a varying water table. Part of the experiments was performed with damaged pipes to simulate leakage conditions common in urban areas and industrial plants. GPR controlled datasets were acquired also in polarization mode, testing the performances for different offset and azimuth. Laboratory analyses (EM properties, radioactivity, chemical analysis, grain size and minerals) were done to implement the database of material properties. All the information were organised in a Database that represents the most complete data source available at the moment. The Database of physical, geochemical and sedimentological properties started from present international bibliography on this argument, which represents the state of art. More than 30 papers concerning acoustic and electric properties of materials were considered. As regards the physical properties of acoustic waves we considered: P or compressional waves velocity, S or shear waves velocity, P waves quality factor Qp, S waves quality factor Qs and density r. For electric properties we collected: the relative dielectric permittivity er, the electrical conductivity s and the magnetic susceptibility c. In addition, sedimentological, electromagnetic, chemical and radioactivity measurements were performed. A database containing the all the acquired geophysical data was developed. It was exploited in the framework of the project for technology development and test of intermediate solutions and final deliverables. A wide range of subsurface conditions, including migration of contaminants, heaps of industrial and urban waste and industrially utilized areas, was thus considered in the test phase. The main problems at the selected sites range from the assessment of volumes of the materials and the characterization of the types of materials to the determination and monitoring of free-phase Non-aqueous liquids (NAPL). Traditional invasive methods (boreholes, trenches) provide localized information at high costs that is difficult to correlate, primarily due to heterogeneity of the materials and associated rapid lateral variations of their characteristics. Determination and monitoring of contamination and associated hazards for groundwater resources are an even more elusive problem that cannot be effectively tackled by conventional and invasive techniques. The goal of the experiments was not only to obtain a comprehensive dataset for the implementation of the database and the test of the technology but also to verify in the field organization, optimisation and limits of the integrated approach. Experiments were completed at the different test-sites to check the applicability of different integrated geophysical techniques. Development of methodological design to define the specifications of the proposed geophysical acquisition and processing system for combined techniques The state-of-art of the application of geophysics for contaminated sites characterization was complete. The first conclusion of this state-of-the-art is that research on geophysics for site investigation is still "under construction". The scientific community is just starting to understand the reality of contaminant-soil interaction and how each geophysical parameter changes with contaminant type, the time it is present in the soil and pore water chemistry. Nevertheless, it is possible to propose a survey methodology. Information related to the site description, the methodology used, etc. was extracted from a representative list of documents and subsequently analysed. The relation between site typologies and geophysical methods was also studied to know more about the applicability of the techniques. First recommendation: a combination of 2 complementary techniques must be applied. Two combinations are useful: - a slow and high resolution technique applied on anomalies detected by a fast but low resolution technique (e.g. electrical tomography with Slingram electromagnetics); - 2 techniques measuring 2 different and not correlated parameters (e.g. seismics and electrical methods). A second general recommendation is that a good site assessment must be carried out by environmental engineers and End users. The site assessment will help geophysicist to decide which technique is the more efficient in this particular context. Thus the Decision Support System (DSS) is a fundamental tool to help this assessment. DSS should focus on a particular problem: the geochemical and physico-chemical environment around the pollutants. It is important to note that for site investigation 5 major problems can be distinguished: - Geological setting - Hydrogeological setting, - Detection of abandoned or working buried utilities or objects (pipes, tanks, ), - Direct detection of dissolved contaminants - Extension of landfill For each problem a number of most promising geophysical methods is proposed, however the selection of the optimal geophysical technique(s) is strongly site and problem dependent. It is proposed to develop new equipment or optimise existing instrumentation that: - has a high resolution and is not sensitive for conductive terrain - works well on hard ground covers (asphalt, concrete) - can look through reinforced concrete - on the one hand are not too sensitive for ground heterogeneities or on the other hand can map the ground hetreogeneities - work well under conditions where physical industrial sources are present (electrical currents, magnetic fields, ground vibrations) - are certified to function in explosive environments. Not all of these conditions are always valid at the same time, but these should be considered as normal industrial conditions. After analysis of the state of the art, the end-user's requirements and in view of the above mentioned problems the HYGEIA Consortium proposes several developments of geophysical methods to overcome the gap between the required specifications and the current possibilities in an effective way. The proposed hardware developments are: - development of a high resolution positioning system that is designed to be used for GPR measurements, for use on industrial sites where GPS can not be applied - development of a portable seismic source for the generation of both P and S waves with sufficient energy that can be used on noisy and difficult accessible industrial sites, - adaptation of the technology of «gimbal geophones» for continuous SASW field measurements on sites with a hard cover, - development of a broad spectrum low frequency radar antenna that is aimed at increasing the penetration of radar waves (especially in conductive and heterogeneous terrains), - adaptation of capacitative electrode techniques for measurement on terrains with a hard cover on industrial sites, - development of impolarisable electrodes for measuring induced and spontaneous polarisation on terrains with a hard cover. The proposed software developments are: - development of GPR data processing algorithms that enhance the signal-to-noise ratio, e.g. coherent noise and reverberation removal - GPR attribute analysis for potential direct detection of polluting materials - development of an algorithm for migration of radar data : 3D migration for a detailed reconnaissance of buried utilities and 2D migration with a dip controlled operator - development of a user friendly interface for the processing and interpretation of SASW data - development of a user friendly interface for the processing and interpretation of self-potential data - the development of more cost-effective bore hole to bore hole geophysical techniques on industrial sites where surface techniques can not be applied. Creation of database of brownfields and contaminated-site characteristics, definition of end-users requirements and definition of the site typologies The analysis of the brownfield typologies has been aimed at collecting the widest range of data that usually are gathered when a site environmental characterization is carried out. A database of brownfields and contaminated sites characteristics has been created to focus the remedial evaluation steps and to plan management and rehabilitation.A set of requirements on qualitative and quantitative information, flexibility and applicability, accessibility constraints and requirements on costs and time of investigations that the geophysical investigations will meet, has been aimed in order to be useful and convenient with respect to conventional investigation methods for environmental assessment. Requirements have been also designed for the application of geophysical measurements to validate the effectiveness of remediation and for post-remedial monitoring programs at regular time interval. Definition of site typologies, that can be used to calibrate the new technologies and to design/test geophysical procedures for the sites assessment, has been also achieved. The selection has been performed according to the following criteria: 1. Diffusion of the typology, to extend experiment opportunities and to favour the impact on the exploitation of the methodological results by end-users; 2. Expected probability of success and expected benefits form integrated geophysical measurements. Decision support system to guide the end-user in the optimal selection of integrated techniques The GDSS, called GeoPASS is prepared using ms-excel. It includes modules for Resistivity Surveying (RS), Ground Penetrating Radar (GPR), High Resolution Seismic Reflection (HRS), Surface Waves Analysis (SASW) and Electrical Resistivity Tomography between boreholes (ERT), Electromagnetic and Time domain Electromagnetic and object detection (magnetometer and metal detector). A technical description is prepared as well; including a definition of all required input data (currently used for proposed Hygeia fieldwork sites), a general decision flow path and decision flow path for the different geophysical techniques. GeoPASS includes a database containing physical properties of various rocks and sediments and of various pollutants. It contains for each lithology the average value and its variation of the physical properties. The database has an advisory role for the user so the GDSS can be used even when not all the parameters in the database are known. The proposed HYGEIA technology may substantially reduce the costs of rehabilitation thanks to complete 3-D non-invasive imaging of the subsurface by means of integrated geophysical techniques. In order to achieve this a good site assessment must be carried out by environmental engineers and end users. The site assessment will help geophysicist to decide which geophysical technique is the more efficient in this particular context. The Decision Support System GeoPASS is a fundamental tool to help this assessment and ensure effective application of the proposed geophysical technologies. Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
