Subsurface Methods

Our Methods

Practical ground investigation methods spanning geophysics, drilling, sampling and utility surveying. Helping teams better understand subsurface conditions.

Close-up of field equipment used in geophysical methods, including survey spikes and cable for non-invasive subsurface characterization and data collection supporting geophysical investigations and mapping.

Geophysical Methods

Geophysical methods measure variations in physical properties such as electrical resistivity, magnetism, seismic velocity, and electromagnetic response. These non-invasive technologies image subsurface conditions, helping engineers, environmental professionals, and mine operators understand geology, groundwater systems, and hidden infrastructure before drilling or excavation begins.

Electrical Resistivity

Electrical resistivity imaging maps variations in subsurface conductivity, revealing changes in geology, groundwater, moisture, and buried features.

Induced Polarization

Induced polarization surveys measure chargeability and resistivity, helping identify variations in subsurface materials and geologic conditions.

Ground Penetrating Radar (GPR)

Ground penetrating radar measures reflected electromagnetic signals from subsurface materials, helping map buried utilities, structural features, and shallow subsurface conditions.

Electromagnetic Induction

Electromagnetic induction measures conductivity responses in subsurface materials, helping map geologic variations, buried infrastructure, and groundwater conditions.

Magnetotellurics (AMT)

Magnetotellurics measures natural variations in the Earth’s electromagnetic field, helping map deep geologic structures and regional subsurface conductivity.

Nuclear magnetic resonance (NMR)

Nuclear magnetic resonance measures hydrogen responses in groundwater, helping map aquifer properties, water content, and subsurface permeability.

Technician using hammer source and geophone cable during seismic methods survey to measure wave travel through subsurface materials for characterization of structure, stiffness, and depth variations across rugged terrain.

Seismic & Acoustic Methods

Seismic and acoustic methods measure how energy waves travel through the subsurface. Variations in wave speed and response reveal differences in soil, rock, and structural conditions, helping map subsurface layering, material properties, and geologic features important for engineering, infrastructure, and geotechnical investigations.

Seismic Refraction

Seismic refraction measures changes in seismic wave velocity, helping map subsurface layering, bedrock depth, and variations in soil and rock properties.

Seismic Reflection

Seismic reflection measures returning seismic wave energy from subsurface boundaries, helping map geologic layering, structure, and subsurface conditions.

Multichannel analysis of surface waves

Multichannel analysis of surface waves measures surface wave dispersion, helping map shear wave velocity and variations in soil and rock properties.

Person hiking on rocky terrain with hiking poles under a clear blue sky.

Potential Field Methods

Potential field methods measure natural variations in the Earth’s gravitational and magnetic fields. These passive geophysical techniques help map subsurface density and magnetic property contrasts, supporting regional geologic mapping, mineral exploration, and identification of buried structures and geologic features.

Magnetic surveys

Magnetic surveys measure changes in subsurface magnetic properties, helping map geologic structure, buried infrastructure, and variations in rock composition.

Gravity surveys

Gravity surveys measure subtle changes in gravitational acceleration, helping map variations in subsurface density, geology, and structural features.

Worker in safety gear checks underground utilities with equipment on a grassy area by a sidewalk.

Direct Investigation Methods

Direct investigation methods provide field verification of underground conditions through visual inspection, locating tools, and controlled excavation. These techniques help confirm utility locations, map underground infrastructure, and document subsurface conditions, supporting safer excavation planning, improved coordination, and reliable documentation of buried assets.

CCTV Inspection

CCTV inspection uses camera systems inside pipelines, helping identify pipe condition, structural defects, blockages, and underground infrastructure connections.

Sonde locating

Sonde locating uses an electromagnetic transmitter inserted into pipelines, helping map underground pipe routes and infrastructure connections.

Potholing / vacuum excavation

Potholing uses vacuum excavation to safely expose buried utilities, helping confirm utility location, depth, and type before construction.

Utility Survey & Mapping

Utility surveys use locating tools and field measurements, helping map underground infrastructure and document buried utility networks.

Workers in safety gear operate equipment at a construction site.

Drilling Methods

Drilling methods provide direct access to subsurface conditions for sampling, monitoring, and geotechnical investigation. Techniques such as auger, rotary, hammer, core, and direct push drilling allow teams to collect soil, rock, and groundwater data needed to support engineering, environmental, and site characterization projects.

Auger

Auger drilling uses rotating helical blades to advance boreholes, helping collect soil samples and characterize shallow subsurface conditions.

Rotary

Rotary drilling uses a rotating drill bit and circulating fluids, helping advance boreholes through soil and rock for subsurface investigation.

Hammer

Hammer drilling uses percussive impacts with a rotating bit, helping advance boreholes through hard rock and fractured formations.

Core

Core drilling cuts cylindrical rock samples from boreholes, helping analyze rock properties, geologic structure, and subsurface conditions.

Direct Push

Direct push uses hydraulic force to advance sampling tools into soil, helping collect subsurface samples and evaluate environmental conditions.

Worker in high-visibility gear carries coiled cables in a rocky, dry landscape with sparse trees.

Sampling Methods

Sampling methods collect soil, rock, and groundwater materials directly from the subsurface for laboratory analysis. These techniques support environmental studies, geotechnical investigations, and site characterization by providing physical samples that help engineers and scientists evaluate material properties, contamination, and subsurface conditions.

Soil sampling

Soil sampling collects subsurface soil materials from boreholes, helping evaluate soil properties, stratigraphy, contamination, and site conditions.

Rock core sampling

Rock core sampling extracts cylindrical rock cores from boreholes, helping evaluate lithology, rock structure, and subsurface geologic conditions.

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