The Membrane Interface Probe (MIP) and the Hydraulic Profiling Tool (HPT) are both powerful geotechnical site investigation tools in their own right. With the introduction of the MiHpt system (combined MIP-HPT probe), production rates double as the two systems become one. Numac Drilling Services has just commenced operation of the new MiHpt data collection system, and clients have been impressed with the effective correlation of VOC and hydraulic inputs.

The probe is robust and percussion drivable (hammerable) with Geoprobe® direct push machines. Daily production rates exceed standard sampling techniques, ensuring site assessments are completed in shorter time frames than conventional drilling surveys.

The MiHpt system effectively detects volatile contaminants with the MIP, measures soil electrical conductivity with a standard MIP dipole array, and measures HPT injection pressure using the same down-hole transducer as the Geoprobe® stand-alone HPT system.

In post-processing the log data, users can estimate hydraulic conductivity (K) and water table elevation, and prepare graphical outputs. This high-density data output makes the MiHpt system ideal for use with modelling software and facilitates quick and accurate conceptual site model development in both 2D and 3D.


To conduct effective site environmental site assessments (industrial facilities, petrol stations, landfills, etc.), and then move forward with remediation design plans, drilling contractors must gain comprehensive knowledge of the site’s vertical profile. This is why we use the membrane interface probe, which delivers benefits such as:

  • Fast, continuous, real-time profiling of soil subsurface

  • Effective on volatile organic compounds (VOCs) such as halogenated solvents (PCE, TCE) and petroleum (BTEX) compounds.

  • Real-time data output to all stakeholders

  • Suitable for both saturated and unsaturated conditions

  • Built to hammer with standard Geoprobe® machines

  • Provides a simultaneous log of conductivity with integrated dipole array

  • Parameters are displayed and stored on the laptop computer for future analysis

  • Data can be incorporated into 2D or 3D visualisations in real time for quick decision-making in the field.

MIP technology can be used at virtually any site, under any condition (indoor, outdoor, difficult access, etc.), such as:

  • Brownfields sites

  • Petrol/fuel retail stations and petroleum depots

  • Manufacturing facilities, warehouses, and other industrial sites

  • Railroads

  • Defence sites

  • Landfills

  • Environmental pre-remediation and post-remediation assessments.

Data is collected in real time at a rate of 65 readings per metre (with no vertical data gaps) to accurately identify zones of contamination and pinpoint natural and manmade preferential pathways in the subsurface. This data can then be incorporated into 2D and 3D graphics for real-time visualisation of subsurface contaminant plumes.


MIP GC 2000

MIP GC 2000

As a continuous VOC sampling system which heats the soil, water, and vapour matrix as it’s driven into the subsurface, the membrane interface probe maps contaminants within the groundwater and surrounding soil. The VOC mass (extracted across a semipermeable membrane) is carried to the surface by an inert purge gas via small diameter inert tubing. After reaching the surface, the compounds are analysed by a suite of three laboratory grade detectors. This innovative and technologically advanced sensor detection system includes:

  • Photo Ionization Detector (PID)

  • Flame Ionization Detector (FID)

  • Halogen Specific Detector (XSD)

The three detectors combine to deliver a range of sensitivities that discriminates between different compound classes — anything from chlorinated solvents to gasoline hydrocarbons to methane soil gas — with the use of multiple detectors important for separating different types of contamination. The complementary performance range of the different detectors enables the MIP system to function from low contaminant levels to near NAPL levels.

Additionally, the inclusion of the Electrical Conductivity (EC) probe indicates general soil particle size which helps to identify sand, silt and clay zones. Using the EC logs, site assessors can define lower conductivity zones which allow contaminants into the subsurface.