A realistic resaturation of the seal is an essential element of the "proof of concept" of the "engineered gas transport system" (EGTS). The combination of the geological/hydrogeological conditions at the GTS, the technical infrastructure and the possibility to establish hydraulic/gas pressures similar to those in a future L/ILW repository provides ideal conditions for the GAST experiment. Particularly important for a realistic simulation of the resaturation process is the high water injection pressure of more than 5 MPa. While this can be implemented at the GTS, it could not, for example, be applied at the Mont Terri rock laboratory without impairing the integrity of the surrounding rock.
Several potential sites at the GTS fulfill the requirement of having practically no excavation induced fracturing of the tunnel walls. Eventually, the rock conditions in the WT tunnel section were found to be most favourable.
Map of the GTS tunnel system with the GAST experiment site at the end of the WT tunnel
360 view of Gast in Grimsel. Drag to rotate image.
The GTS underground facilities are also available to interested 3rd parties for underground testing and research. The GTS offers cost-effective access to a fully developed, well characterised underground research facility with round the year logistical support - please contact Dr. Ingo Blechschmidt, Head of the Grimsel Test Site, for further details.