Monitoring of diesel displacement in the plurimetric pilot (PPM/PRIME) as part of the SPLODGE project. © BRGM – D. Depoorter
First erosion measurement survey at the foot of the Bonifacio cliffs
The General Directorate for Risk Prevention has entrusted BRGM with monitoring the erosion of the Bonifacio cliffs in southern Corsica. The purpose is to specify the rate of erosion of the foot of the cliff. As the calcareous sandstone erodes grain by grain, the researchers use photogrammetric analysis at a resolution of less than a millimetre. A field assignment took place from 6 to 10 June 2022. Six monitoring plots (areas of 10-15 m² precisely delimited and located for experimental research) were set up in areas with different erosion contexts, with twelve targets per plot to measure the changes on a quarterly basis and after each storm. A second assignment is planned for 2023 to install oceanographic and hydromechanical sensors to finely characterise the wave regime near the cliff and measure the impacts on the wall.
TURNkey, a multi-sensor platform to characterise seismic risks in real time
BRGM participated in the European TURNkey project that uses a multi-sensor platform to characterise seismic risks in real time: during the occurrence of an earthquake for early warning or just afterwards for rapid response purposes. The sensors used were accelerometers, GPS receivers, low-cost RaspberryShake seismic sensors, feedback from citizens, etc. The group of researchers concentrated on improving the rapid response procedures by developing a system to update seismic movement maps (ShakeMaps) and to predict damage and losses on the basis of feedback from the field immediately after an earthquake. The Bagnères-de-Luchon region served as a pilot site, notably through the deployment of a dozen RaspberryShake-4D seismic sensors in strategic buildings and on road infrastructures.
SPLODGE, characterising the distribution of hydrocarbons in the groundl
Petrol, diesel, engine oil, etc.
Improving the diagnosis of hydrocarbon-polluted soils and groundwater is a major environmental challenge. The purpose of the SPLODGE project, abbreviated from SPiLl mODeling Geophysic hydrocarbon dEtection, is to better characterise the distribution of hydrocarbons in the ground to improve diagnosis and remediation through non-intrusive and general geophysical methods coupled with multiphase modelling. The experiments took place in the MultiMetric Pilot (Pilote PluriMétrique or PPM) of the BRGM PRIME platform. The project brought together and was funded by the Centre-Val de Loire Region, the AnteaGroup and BRGM.
SPASE, a flood and erosion forecasting and warning system
How can the consequences of a forecast storm be anticipated in just a few days in terms of flooding and eventual erosion? The Pôle métropolitain de la Côte d’Opale (Côte d’Opale Conurbation Unit) has asked BRGM to study the feasibility of a flood and erosion forecasting and warning system for the Hauts-de-France coastline. The challenge addressed by the SPASE project is to assess the most innovative methods for meeting this type of operational need according to the objectives of the partners: decision-making support for local authorities, State services and other potential users. How? In particular, by studying the possible technical solutions, the implications in terms of governance and responsibility and the appropriate economic models. Currently being adapted for the Joint Seine-Maritime Coastal Association (Syndicat mixte du littoral de la Seine-Maritime) in this département, the modular approach proposed by BRGM should lead in the medium term to the operational use of such a tool in northern France.
Cap Gris-Nez is a typical study area for warning of the risk of erosion and submersion. © BRGM
GUYACLIMAT, the impact of climate change on French Guiana
With GuyaClimat, BRGM and Météo-France are seeking to characterise the impact of climate change on French Guiana with regard to various physical parameters: sea level, temperature, precipitation, wind and waves. Projections of future developments have been made on the basis of global models from the IPCC (Intergovernmental Panel on Climate Change). The results include a possible sea level rise of about 0.84 m in 2100 compared to the mean for the period from 1986 to 2005, with consequent chronic coastal flooding hazards. The low-lying areas at risk have been mapped for three municipalities for 2050 and 2100.
Example of a map of low-lying areas potentially exposed to chronic submergence, produced here for Cayenne and the RCP4.5 scenario for 2100. © BRGM
New Caledonia: BRGM is studying the impact of nickel and cobalt mining on water resources
In 2021, BRGM was asked by Prony Resources New Caledonia (PRNC) to carry out expert assessments to answer several questions posed by the New Caledonian Department of Industry, Mines and Energy (DIMENC) on the consequences of PRNC’s mining activities in terms of water pollution. The stakes are very high for these studies: they are part of a conflict resolution process with part of the local population. The three reports produced by BRGM led in particular to recommendations on improving and implementing measures to limit the impact of nickel and cobalt mining on water resources. The objectivity and quality of the work carried out, presented on site by three of the BRGM experts involved, was such as to reassure the local populations.
Summary of a hydrogeological assessment to measure the risk of groundwater disturbance linked to PRONY’s mining operations, particularly on the Goro tribe and Plaine des Lacs. © BRGM
FAMOUS project: foam injection for blocking aquifers to treat heterogeneous groundwater
In partnership with the universities of Bordeaux and Franche-Comté, Solvay France, Serpol and Ademe and as part of the GESIPOL/FAMOUS project, BRGM has experimentally and numerically studied the injection of foam to divert the flow of groundwater upstream from a contaminated area in order to carry out effective in situ treatment downstream. Restricting the flow increases the contact time between the injected reagents and the pollutant in highly permeable mediums with often high flow rates. The overall results (in the form of six A-ranked papers) show that the use of foam as a blocking fluid in high-permeability soil remediation is highly promising.
Sample preparation for foam testing. © BRGM – C. Boucley
Post-mining / Renewal of the contract delegating responsibility for the management of safety engineering work in abandoned mine sites to BRGM/DPSM.
BRGM’s mission as the State’s delegated project manager for safety work on former mining sites was extended for six years by the French Ministry of Ecological Transition and Territorial Cohesion, which is responsible for these issues (Decree No. 2022-977 of 1 July 2022, published in the Official Journal on 3 July 2022). The DPSM, BRGM’s Mine Safety and Risk Prevention Department, has been carrying out this mission since 2006. The renewal of this contract by the Ministry shows its confidence in DPSM as the long-standing public operator in the field of post-mining operations.
Post-mining / Use of satellite interferometry for post-mining
Satellite-based interferometric Synthetic Aperture Radar (InSAR) is a tool that complements (or can even be used as an alternative to) traditional techniques used to monitor land movements through contour-mapping. This approach was applied by BRGM in order to quantify vertical movements in the Nord-Pas de Calais and Provence coalfields. It detects ground movements of just a few millimetres a year.
Map of vertical ground movement velocities - Nord-Pas de Calais coalfield - period 2015-2018 (Sentinel-1 data). © BRGM
Post-mining / Securing the Moïse mine shaft in Rive-de-Gier
The Moïse shaft is 180 metres deep and the structure dates back to the coal mining era in the Gier valley (Loire). Located close to a hangar, the pit head was beginning to collapse. Securing the structure involved creating a self-supporting cap. A permanent formwork system was put in place by divers at a depth of 12.5 metres, and a concrete cap was poured in, over several stages. The site was duly restored and a sign was put in place informing people of the existence of the old structure.
Diver descending into the Moïse shaft in Rive-de-Gier (Loire). © BRGM
Post-mining / Work on the Sainte-Barbe shaft in Bézenet
The Sainte-Barbe mine shaft in Bézenet (Allier département) – a former coal mine with a depth of more than 400 metres – had already undergone initial safety work to fit a conical concrete cap on the pit-head. After problems appeared around the infill area, the old cap was removed and a self-supporting friction cap (twenty metres high) was put in place. A special feature of this work was that, in order to avoid exposing personnel to the highly unstable walls of the shaft, the concrete cap was set on a high-capacity inflatable plug.
Post-mining / Rehabilitation of the Saumoduc (brine pipeline) in the Alsace potash basin
During mining operations in the potash deposit in the north-western sector of Mulhouse, mine tailings were stored on the surface and some of the salt contained in these tailings dissolved and infiltrated into the soil. To prevent it from spreading into the water table, the salt water is pumped out and then discharged into the Rhine, where dilution reduces the environmental impact. The brine passes along an overhead concrete canal some twenty kilometres long: the Saumoduc. The canal underwent rehabilitation work from 2019 to 2022 to ensure its watertightness. The main work carried out involved repairing the concrete structure and installing a geomembrane sealing system.
Installation of the water-tight geomembrane in the Saumoduc d’Alsace pipeline (Haut Rhin). © BRGM