What matters most
Wenner stations should represent proposed grounding facilities, route segments, changes in soil or terrain, cut-and-fill zones, drainage settings, and accessible native ground. The plan also needs enough straight-line distance for the required spacings and backup directions when utilities, pavement, fences, or operations block the intended array.
Key takeaways
- Start from the project layout and data use.
- Represent distinct grading, geology, drainage, and facility zones.
- Preserve open distance for the largest spacing.
- Document relocations instead of hiding field changes.
Overlay the test plan on the proposed facility
Mark the ground grid, equipment pads, collector system, transmission structures, buried utility route, pipeline, or investigation area. Then identify the areas whose earth behavior could change the design or interpretation.
A single station outside the disturbance area may not represent imported fill, a retention basin, a cut slope, a river crossing, or a large facility extending across several mapped units.
Use available subsurface information before mobilization
Review borings, geologic mapping, grading plans, historical aerials, utility plans, groundwater observations, and soil descriptions. These do not replace measurements, but they help place stations where the survey can test meaningful contrasts.
Avoid blending every difference into one composite answer. Label stations by project zone so the receiving engineer can decide whether separate models are needed.
Plan controlled field adjustments
Access changes, crops, wet ground, rock, traffic, equipment, new utilities, or restricted areas may prevent the planned line. Establish acceptable move distances, alternate directions, and the person authorized to approve major changes.
Record the actual coordinates, line orientation, reason for relocation, and what the revised station represents. Good field judgment is valuable only when it is traceable.
Send CAD or PDF plans with the proposed facilities, property limits, existing utilities, and requested spacings. Layout review before travel often prevents an unusable station.
This page provides general educational information, not a grounding-system design, cathodic-protection design, installed-system acceptance test, or parcel-wide resistivity conclusion. A Wenner result is apparent soil electrical resistivity for the documented array, spacing, location, orientation, and field condition. The responsible grounding or corrosion engineer must evaluate the complete dataset, earth model, asset geometry, governing documents, and uncertainty.
Frequently asked
Questions about this topic
How many stations does a project need?+
There is no universal count. It depends on facility size, variability, target model, consequence, available information, and governing criteria.
Can testing be done before final grading?+
Yes, but the report should distinguish existing native ground from future cut, fill, imported material, and finished-grade conditions.
Should stations be placed only inside the future grid?+
Not always. The grounding engineer may need representative lines within, beside, or beyond the facility depending on layout and available clear distance.
Primary references and further reading
- ASTM International — ASTM G57-20 Official record for the Wenner four-electrode field and four-electrode soil-box method.
- IEEE Standards Association — IEEE 81-2025 Current IEEE guide for measuring earth resistivity, grounding-system impedance, and earth-surface potentials.
- Soil Tests Laboratory — Wenner Four-Pin Testing Calicore Engineering’s testing division and field-service information.