Cardiff's geology is shaped by glacial till overlying Mercia Mudstone and the Wentloog Formation, creating variable groundwater conditions across the city. In areas like the Cardiff Bay basin, the water table sits less than 2 metres below ground, while the elevated northern suburbs see deeper levels and perched aquifers. Effective geotechnical drainage design must account for these contrasts: high plasticity clays can trap water, reducing bearing capacity, while granular deposits in the Taff valley risk piping erosion. Before any drainage system is sized, we run field permeability tests and install standpipes to map phreatic surfaces. This data feeds directly into our stability analysis for retaining walls, ensuring that hydrostatic pressures are fully controlled in cut slopes and basement excavations across Cardiff.
High plasticity clays in Cardiff can trap water for weeks after rainfall, so drainage design must account for transient pore pressures, not just static water tables.