Electrical Resistivity Testing (VES) in Melbourne

Q: Can resistivity surveys detect groundwater in Melbourne's aquifers?

Yes, resistivity is sensitive to pore water salinity and saturation. A sharp drop in resistivity with depth often marks the water table. In the Port Phillip basin, the transition from dry silty clay (40–80 ohm·m) to saturated sand (10–30 ohm·m) is clearly identifiable on a 2D pseudo-section. This makes VES a cost-effective tool for hydrogeological assessments before dewatering design.

Melbourne's geology is defined by Quaternary basalts in the west and Silurian mudstones to the east, with the Yarra River floodplain depositing soft alluvial clays and silts up to 30 meters deep in places. These contrasting ground conditions make electrical resistivity / VES surveys particularly valuable for mapping subsurface stratigraphy without drilling. The method identifies changes in resistivity between basalt, clay, sand, and groundwater, providing a continuous profile of the ground. Before committing to boreholes, many project teams run a georradar survey alongside resistivity to correlate shallow anomalies, and a [MASW survey](/masw-vs30/) when shear-wave velocity data is also needed for seismic site classification. In Melbourne, this combined approach reduces uncertainty in early-stage design.

Illustrative image of Electrical resistivity / VES (Vertical Electrical Sounding) in Melbourne

Resistivity surveys in Melbourne's western basalt plains identify buried rock profiles and groundwater pathways without a single drill hole.

Our service areas

Ground improvement

Unsaturated soil analysis ›Stone column design ›Dynamic compaction design ›Deep Soil Mixing (DSM) design ›Geotechnical drainage design ›

VIEW ALL GROUND IMPROVEMENT ›

Slopes & Walls

Soil erosion analysis ›Slope stability analysis ›Slope failure analysis ›Debris flow analysis ›Factor of safety (FS) calculation ›

VIEW ALL SLOPES & WALLS ›

Foundations

Differential settlement analysis ›Settlement analysis ›Bearing capacity analysis ›Foundations on fill (analysis) ›Shallow foundation design ›

VIEW ALL FOUNDATIONS ›

Methodology and scope

Melbourne's rapid suburban expansion since the 1990s has pushed development onto former wetland and basalt plains, where hidden layers of soft clay or fractured rock can compromise foundations. Electrical resistivity / VES surveys map these layers quickly: electrodes are laid in a line, current is injected, and the apparent resistivity measured at increasing electrode spacings produces a vertical pseudo-section. The team processes data using inversion software to generate true resistivity models down to 50 meters depth. For projects in the western suburbs where basalt caprock is common, resistivity helps locate the basalt–clay interface, a critical boundary for pile design. Fieldwork follows AS 1726 ground investigation procedures and typically takes one day for a 200-meter line. The output integrates with borehole logs to build a reliable ground model before detailed design begins.

Technical reference — Melbourne

Local considerations

AS 1726 requires that ground investigation methods be appropriate for the expected ground conditions. Relying solely on boreholes in Melbourne's variable geology can miss thin clay lenses or perched water tables that cause differential settlement. Electrical resistivity / VES surveys reduce this risk by providing continuous lateral coverage, highlighting anomalies between boreholes. The method is particularly relevant on the Mornington Peninsula, where shallow basalt over weathered clay can mask cavities. Combining resistivity with limited borehole control meets the standard's intent for a representative investigation and avoids the cost of unexpected ground conditions during excavation.

Need a geotechnical assessment?

Reply within 24h.

Email: contact@geotechnicalengineering1.vip

Explanatory video

Applicable standards

AS 1726:2017 Geotechnical site investigations, AS 1289 Standard test method for field measurement of soil resistivity, AS/NZS 1170.0:2002 Structural design actions – General principles

Technical parameters

Parameter	Typical value
Array configuration	Wenner, Schlumberger, or dipole-dipole
Maximum depth of investigation	Up to 50 m depending on spread length
Electrode spacing	1 m to 10 m
Measurement points per line	50–120 readings
Data output	1D inversion model (VES) or 2D pseudo-section
Field time per 200 m line	4–6 hours with two technicians

Frequently asked questions

How deep can an electrical resistivity / VES survey reach in Melbourne soils?

With a standard 200-meter spread, VES surveys in Melbourne typically reach 40–50 meters depth. In conductive clay-rich ground such as the Yarra floodplain, depth reduces to around 30 meters due to signal attenuation. Deeper penetration is possible using larger electrode spacings and higher transmitter power, but that requires longer field time and road closures for traffic management.

What is the typical cost range for a resistivity survey in Melbourne?

A standard VES survey for a residential block in Melbourne costs between AU$840 and AU$1,760, depending on the number of soundings and site access. A 2D imaging line over 200 meters typically ranges from AU$1,800 to AU$3,200. These are indicative rates; a formal quote is provided after a site visit to assess access, vegetation, and utility clearance requirements.

How does resistivity data integrate with borehole information?

Resistivity models are calibrated against borehole logs to convert resistivity values into interpreted soil or rock types. For example, in Melbourne's basalt plains, high resistivity (>200 ohm·m) typically corresponds to fresh basalt, while low resistivity (<30 ohm·m) indicates saturated clay. The calibrated model then extends borehole interpretations laterally, reducing the number of boreholes needed for a given site.

Can resistivity surveys detect groundwater in Melbourne's aquifers?

Yes, resistivity is sensitive to pore water salinity and saturation. A sharp drop in resistivity with depth often marks the water table. In the Port Phillip basin, the transition from dry silty clay (40–80 ohm·m) to saturated sand (10–30 ohm·m) is clearly identifiable on a 2D pseudo-section. This makes VES a cost-effective tool for hydrogeological assessments before dewatering design.

Location and service area

We serve projects across Melbourne.

Location and service area