Geological modelling of Quaternary deposits in West Cumbria, UK to support Low Level Waste Repository environmental safety case.

The Low Level Waste Repository in West Cumbria disposes of low-level radioactive waste within the UK. The site requires, as part of their environmental safety case, a geological model to support hydrogeological modelling and future development of the site. Primarily the geological model must represent the variation in the sub-surface that is applicable to the groundwater, and therefore potential contaminant transport. Of particular importance are the properties and extents of the material, grouped into stratigraphic units. Recent work has been undertaken to produce an updated geological model to support the environmental safety case submission in 2026. This work included a 3D digital geological model that utilises the benefits of the volume of data collected, both legacy and more recent additional data collection, and software developments since the previous safety case submission. Boreholes, multiple geophysical datasets (including reflection, refraction, ERT and passive methods), geomorphology and sections are all interpreted within a stratigraphic framework for geological modelling. The stratigraphy applied groups lithologies of similar hydrogeological parameters, with consideration of the depositional and deformational processes, glacial events and land systems to support prediction of extents and thickness variation. Consideration of these processes supports explicit control of the digital geological model away from available observational data. The work also addresses ongoing debate surrounding the depositional environment of the near surface Quaternary deposits, identified in this work as an Ice Dammed Lake sequence limited in extent to a couple of kilometres of the repository site. The talk will discuss the recent work in more detail, providing a brief overview of the history of the site, data collected, model development, interpretations, and key findings.