Accurate detection and characterization of organic soils play a crucial role in ensuring the stability and safety of infrastructure projects, particularly linear constructions such as highways, railways, and pipelines. Due to their high compressibility and variable properties, organic soils pose significant challenges for geotechnical design and foundation engineering. While borehole investigations provide localized data points, they often fail to capture the continuous spatial variability of these soils, leading to potential uncertainties and construction risks. This study demonstrates the advantages of integrating geophysical techniques, with a focus on Electrical Resistivity Tomography (ERT), to achieve detailed mapping of organic soil layers. Through several case studies from Poland’s major infrastructure developments, the paper illustrates how geoelectrical methods complement traditional borehole data to enhance soil profiling accuracy. The combined approach enables early identification of problematic zones, optimizing investigation efforts and reducing unexpected complications during construction. Challenges related to similar resistivity signatures of organic soils and adjacent deposits are addressed by careful interpretation and supplementary methods when necessary. The findings confirm that geophysical surveys are cost-effective, non-invasive tools that significantly improve the reliability of geotechnical models, particularly for extensive linear projects where comprehensive direct testing is impractical. This integrated methodology supports better foundation design choices and mitigates risks associated with weak, organic soil layers.