Summary

An electrical resistivity survey showed that the foundation conditions were more complicated than indicated by preliminary borehole information. The results of resistivity traversing, which was completed in a few days at comparatively little cost, clearly indicated that a sand and gravel layer, which had been proved at each borehole, was absent from at least one third of the site. Also, resistivity depth probes enabled the thickness of peat and soft clay, overlying the sand and gravel layer, to be calculated with remarkable accuracy. The problems of determining the thickness of the sand and gravel with suitable accuracy and of distinguishing silt from sand and gravel were unfortunately not resolved by these geoelectrical methods.