Electrical Resistivity Testing & Vertical Electrical Sounding in Gloucester

With a maximum current electrode half-spacing (AB/2) of 200 metres, we typically achieve investigation depths between 40 and 60 metres in Gloucester's alluvial and Lias Clay sequences. The practical limit depends on site access—we need clear runs of 300 to 400 metres for the full spread. For shallower targets, such as mapping the gravel-clay interface at 4 to 8 metres, a smaller array is faster and equally effective.

For a typical Gloucester site investigation, VES and 2D resistivity surveys range from £450 to £930 depending on the number of soundings, line length, and processing requirements. A single VES point with interpretation starts toward the lower end; a full 2D tomography line with topographic correction and report approaches the upper end. We provide fixed-price quotations after reviewing your site plan.

Surface moisture after rain improves electrode contact and reduces contact resistance, which is generally beneficial. However, saturated near-surface conditions can mask deeper resistivity contrasts. We schedule surveys with consideration to recent rainfall and include weather notes in our reports. Winter surveys in Gloucester's clay-rich soils often produce excellent data because the clay matrix holds consistent moisture content.

Yes, and this is one of the most useful applications in Gloucester. Saturated Lias Clay typically registers 15 to 35 ohm-m, while dry to moist River Terrace Gravels range from 80 to over 600 ohm-m. The contrast is sharp enough that the gravel-clay interface appears as a clear inflection in the resistivity-depth curve, allowing us to map the thickness of alluvial cover across a site with confidence.

We routinely recommend calibrating resistivity profiles with at least one or two boreholes or test pits. The geophysics identifies the lateral extent of features; the physical investigation confirms what those features are. For Gloucester sites, we often pair resistivity with CPT soundings for continuous mechanical data, or with laboratory testing of recovered samples to correlate resistivity values with specific lithologies.