Refined geological and hydrogeological models to resolve surface and underground impacts of the Einstein Telescope facility in the Euregio–Meuse Rhine (EMR) region

The Einstein Telescope is a proposed underground facility that will serve as a third-generation gravitational waves observatory. The Euregio – Meuse Rhine (EMR) bid proposes the construction of a triangular array with 30 km of tunnels and caverns at depths between 250 and 400 meters below ground surface. A large underground facility such as this can cause significant environmental impacts as groundwater would drain into the tunnels and caverns and would need to be removed. Previous regional modelling estimated that drawdowns in the shallow aquifer could be up to 20 meters.
The EMR area is located in the border region between Belgium, the Netherlands and Germany and the subsurface of the area is complex, containing faulted, fractured and folded sedimenraty rocks. Heterogeneity in hydraulic parameters spans widely within the same stratigraphic units. Based on first regional simulations, initial drainage estimates range from 380 to 48,500 m3/day. To address this uncertainty, refined models have been built based on newly acquired geological and hydrogeological data.
Local refined hydrogeological and geological models are built in concert with each other and regional ones[PO2.1], advancing the hydrogeological interpretation of the subsurface while refining the FEFLOW model discretization to handle calculation of pore pressure and tunnel inflow and subsequent impacts on hydraulic head in all aquifers. It has been developed through detailed interpretations of new and existing data obtained from public sources and within the Einstein Telescope project. Additionally, the mesh for the tunnel and the facility [PO3.1]have been enhanced, improving the solution at the boundary condition and increasing the ability of the model to handle different parameters. Mitigations including grouting around the tunnels and Managed Aquifer Recharge (MAR) are tested in our model to address impacts contributing to feasibility of the project bid.