Knowledge of the subsurface needs to be refined and updated

Geo-Energie Jura SA is embarking on a new phase of its geophysical survey campaign in Haute-Sorne. The aim is to refine and supplement the existing data acquired as part of earlier projects. The data collected will assist with detailed drilling planning and help to ensure the safety of the project.

Geo-Energie Jura SA needs to refine its understanding of the subsurface to ensure the optimal implementation of its deep geothermal project in Glovelier. Whilst data from previous work – notably exploratory drilling carried out at Buix a century ago and at Grandfontaine in 2018, seismic surveys conducted between 1970 and 1980, the construction of the Transjurane tunnels and observations of rock outcrops – provide a good understanding of the region’s geology, it is necessary to supplement this data, validate the current geological model and examine in detail the rock layers traversed by the geothermal borehole. The results of the surveys will help with the detailed planning of the exploratory drilling and contribute to the safety of the project.

Technical resources and information gathered

During the week of 24 July, high-resolution seismic reflection surveys will be carried out in the region. These will provide information on the subsurface structure to a depth of several hundred metres, such as the presence of faults or karst formations. Further survey campaigns will be organised this autumn and winter to provide additional information on greater depths.

A van fitted with a drop-weight device comprising a 250 kg hammer striking an 80 cm high steel plate (identical to the one already used in February 2023) will travel along two perpendicular lines with a total length of approximately 4 km. A drop-weight test will be carried out every 6 metres to send waves into the subsoil. Geophones spaced 2 metres apart and connected by cables will be positioned at the roadside. These geophones will record the waves reflected by the rock layers, providing an image of the subsurface structure in much the same way as an ultrasound scan.

Route and road traffic

The van fitted with the drop-weight device will travel from east to west along the farm track between the Saint-Hubert level crossing in Bassecourt and the Route de la Transjurane in Glovelier. From north to south, it will follow a route between the A16 motorway to the north and the village of Berlincourt to the south.

The works are expected to take four days. They will be carried out by GeoExpert AG of Zurich during normal working hours. The impact on road traffic will be minimal and comparable to the disruption caused by road marking campaigns.

Start of crack surveys as part of the evidence-gathering process

From mid-July, the contractors commissioned by Geo-Energie Jura SA to carry out the crack surveys as part of the evidence-gathering process will be in the testing phase. Property owners who have signed and returned the agreement will be contacted directly by email before the surveys begin. Property owners who have not yet returned the agreement still have until the end of the month to do so.

Furthermore, Geo-Energie Jura is aware that criticism has been voiced in recent weeks regarding the procedures for the crack surveys. The purpose of the crack surveys is not to provide an exhaustive inventory of all the region’s built heritage, but to facilitate the procedures for property owners in the event of damage. We would also like to remind you that numerous precautionary measures are being implemented as part of the geothermal project to ensure that such damage does not occur.

The issue of evidence gathering was addressed during the meetings of the Monitoring and Information Committee (CSI) for the Haute-Sorne project. The documents from these meetings are available online on the CSI website.

Contacts for further information:

Olivier Zingg, Director of Geo-Energie Jura SA, T +41 79 321 43 20 (E+F), [email protected]

Peter Meier, CEO Geo-Energie Suisse AG, T +41 79 248 48 65 (E+D), [email protected]