Geotechnical study in Ribera Baja/Erriberabeitia

In Ribera Baja/Erriberabeitia, soils formed by limestones, dolomites and marbles predominate, accounting for 44.51% of the surface area. These rocky materials, together with the occasional presence of sandstones, conglomerates and flysch, generally provide a good bearing capacity for shallow foundations, provided that areas with superficial alteration are not identified. Fine sands and silts, although common, may have a lower bearing capacity and require additional analysis to prevent differential settlements, whereas compact gravel and sands, although uncommon, also form a good foundation stratum. The existence of masses of water and the low-permeability nature of most formations should be considered in relation to potential impacts from the groundwater level or moisture at depth.

With regard to seismicity, Ribera Baja/Erriberabeitia shows very low activity, with only 4 events in the last 30 years and a maximum magnitude of 1.8; therefore, seismic hazard is not relevant for the design of structures. Since the substrate is not clayey, it rules out the risk of expansiveness, simplifying the conditions for selecting the foundation type. In this municipality, the main aspect to control corresponds to the local geotechnical study characterisation of each site and the possible influence of the groundwater level, rather than exceptional geological risks such as expansiveness or karstification.