Cardiff sits on a landscape shaped by the last Ice Age, with the River Taff and Ely carving deep valleys through glacial till and alluvial deposits. Around 362,000 people live here, and much of the city centre and Cardiff Bay are built on soft, compressible ground. Organic soils — peat, humic clays, and silty loams — are common in the floodplains and former marshlands. Managing these materials properly is essential before any foundation work. Before you pour concrete, a thorough organic soil management plan should include a [permeability field test](/) to understand drainage behaviour in these low-strength layers.
Peat layers under Cardiff Bay can settle more than 200 mm over a decade if not stabilised before construction.