Geotechnical study in La Unión

In the municipality of La Unión, deposits of compact gravels and sands predominate—materials that give the subsoil an excellent bearing capacity for buildings and civil engineering works. These highly permeable soils form part of extensive and productive aquifers, which implies rapid drainage and minimisation of risks due to water accumulation in contact with the foundations. For construction projects, compact gravels and sands represent a favourable setting for shallow foundation, allowing solutions both at surface and at depth depending on structural requirements.

The record of 200 seismic events over 30 years, although with a moderate maximum magnitude of Mmax 3.7, indicates a high level of seismic activity that must be included in the safety calculations for any project. While there are subordinate expansive clays, their limited presence—and, if they do occur, they would be associated with climatic zones where the risk is notably reduced. Thus, the main geotechnical constraint for La Unión lies in seismicity, making it a priority to incorporate anti-seismic criteria into the designs.