GEOTECHNICALENGINEERING
RICHMOND HILL
HomeGeophysicsElectrical resistivity / VES (Vertical Electrical Sounding)

Vertical Electrical Sounding (VES) in Richmond Hill, Ontario

Evidence-based design. Reliable delivery.

LEARN MORE

The subsurface conditions between the Oak Ridges Moraine and the flatter lands south of Major Mackenzie Drive can vary dramatically over a few hundred metres in Richmond Hill. One site might sit on dense Halton Till with a water table at six metres, while another lies over interbedded glaciolacustrine silts and sands where perched aquifers complicate any excavation plan. Before placing a foundation or designing a stormwater infiltration system, understanding this vertical succession of resistivity contrasts is the fastest way to reduce uncertainty. Vertical Electrical Sounding (VES) provides a continuous resistivity profile by expanding electrode spacing stepwise, resolving layer thicknesses and groundwater boundaries without a single borehole. For deeper targets or areas where till thickness is unknown, we integrate VES results with seismic refraction to cross-check bedrock depth and rippability, giving the design team a multi-method picture of what lies beneath the surface.

In Richmond Hill’s moraine landscape, a VES survey often reveals a perched water table within sandy interbeds that borehole logs alone miss—critical information for dewatering design.

Our service areas

Methodology and scope

Richmond Hill’s glacial stratigraphy—dominantly Newmarket Till overlying a complex sequence of Thorncliffe Formation sands and Sunnybrook Drift—produces resistivity signatures that range from 20 Ωm in saturated clay-rich tills to over 200 Ωm in dry sandy lenses. Our field crews deploy a Wenner or Schlumberger array depending on target depth; for typical building investigations we expand AB/2 spacing to 100 metres, achieving penetration beyond 20 metres where the signal-to-noise ratio permits. The method is non-invasive, requires no drilling permits, and generates a one-dimensional resistivity model that identifies low-resistivity clay layers likely to govern settlement, high-resistivity granular zones suitable for infiltration galleries, and the sharp resistivity increase marking the contact with the Paleozoic shale bedrock. All resistivity data are acquired with a Syscal Pro instrument and processed using Res2DInv for quality control, ensuring the interpreted layer boundaries meet the resolution required for geotechnical parameterisation.
Vertical Electrical Sounding (VES) in Richmond Hill, Ontario
Technical reference — Richmond Hill

Local geotechnical context

A recurring mistake on Richmond Hill sites is interpreting a single borehole log as representative of the entire property when buried channels or inter-till sand lenses create lateral heterogeneity that a point investigation cannot capture. We have seen projects south of Elgin Mills where a five-metre-wide sand-filled depression in the till—invisible from the surface and missed by widely spaced boreholes—caused differential settlement that cracked foundation walls within the first year. VES acts as a screening tool that spans tens of metres horizontally, flagging these low-resistivity or high-resistivity anomalies before the drilling program is finalised. Skipping the geophysical step means the geotechnical model relies on interpolation between sparse points, and in Richmond Hill’s subglacial landscape that interpolation is frequently wrong. The cost of a supplementary VES line is negligible compared with the delay and remedial underpinning required when an undetected soft zone compromises a footing.

Need a geotechnical assessment?

Reply within 24h.

Email: info@geotechnicalengineering.co

Applicable standards

ASTM D6431-18 Standard Guide for Using the Direct Current Resistivity Method for Subsurface Site Characterization, Ontario Building Code (OBC) Part 4 — Structural Design, referencing geotechnical investigation requirements, CSA A23.3-19 Design of Concrete Structures — foundation bearing requirements relying on subsurface data, MTO Laboratory Testing Manual LS-600 series (applicable to Ontario infrastructure projects)

Reference parameters

ParameterTypical value
Typical investigation depth (Schlumberger array)1–100 m, depending on AB/2 expansion
Resistivity range resolved1 Ωm (clay) to > 500 Ωm (dry sand, bedrock)
Electrode configurationWenner, Schlumberger, dipole-dipole (per target geometry)
Minimum survey line lengthTwice the target depth (e.g., 40 m line for 20 m penetration)
Data acquisition systemSyscal Pro (10-channel) with stainless-steel electrodes
Data processing softwareRes2DInv / IPI2Win for 1D layered inversion
Reporting standardASTM D6431-18 for resistivity imaging methods

Common questions

How much does a VES survey cost for a standard residential lot in Richmond Hill?

For a typical residential lot requiring two to three sounding locations with AB/2 expansion to 60–80 metres, the cost ranges from CA$810 to CA$1,440. The final figure depends on site accessibility, surface conditions, and the number of soundings required to achieve adequate spatial coverage.

Can VES distinguish between dense till and shale bedrock?

In Richmond Hill, the Newmarket Till often exhibits resistivity values between 30 and 60 Ωm when saturated, whereas the underlying Georgian Bay Formation shale typically falls below 20 Ωm due to its higher clay-mineral content. The resistivity contrast is generally sufficient for a clear interpretation, though we verify with at least one borehole or seismic refraction line on critical projects.

Is electrical resistivity affected by buried utilities or reinforced concrete?

Yes, metallic pipes, reinforced concrete structures, and overhead power lines can introduce noise or distort the apparent resistivity readings. Our field protocol includes a utility-clearance review before layout, and we offset soundings by a minimum of five metres from known metallic infrastructure. Where interference is unavoidable, we apply notch filters during processing and document the potential influence in the interpretation report.

What is the minimum site area needed for a VES sounding?

A single Schlumberger sounding to 30 metres depth requires a clear line of approximately 60 metres in one direction. On smaller urban lots where full expansion is not possible, we can use a Wenner array with shorter lines or combine VES with complementary methods such as test pitting or SPT drilling to constrain the shallow stratigraphy.

How long does field acquisition and reporting take?

Field acquisition for three VES soundings on an accessible Richmond Hill site typically takes one full working day. Data processing, inversion modelling, and report preparation require an additional three to four business days. We deliver a signed, stamped report including resistivity curves, interpreted layer models, and correlation with available borehole logs or geological mapping.

Location and service area

We serve projects in Richmond Hill and surrounding areas.

View larger map