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Understanding the Challenge of Soil Contamination Investigation

Soil contamination investigation requires more than locating a single abnormal point. Environmental teams often need to understand subsurface structure, identify areas that merit further verification, and determine where to prioritize drilling, soil sampling, or groundwater sampling.

Boreholes and laboratory analysis remain essential for confirming contaminant type and concentration. However, borehole data is point-based, while subsurface conditions can vary significantly between sampling locations. Electrical Resistivity Tomography (ERT) can complement direct investigation methods by mapping variations in subsurface electrical resistivity across continuous survey lines.

ERT does not independently identify a contaminant or confirm a pollution boundary. Instead, it provides geophysical evidence that should be interpreted together with site history, geological and hydrogeological information, sampling data, and engineering judgment.

GD-20 for Multi-Channel Resistivity Surveys

Geomative’s GD-20 Electrical Resistivity System is designed for resistivity, induced polarization, and self-potential survey applications. The system uses an independent 5/12-channel design. In ERT mode, it supports up to 10-channel data acquisition; in VES mode, it can test up to 12 sets of sounding points simultaneously.

Compared with single-channel equipment, the GD-20 is described as delivering an average field testing-efficiency increase of 2–3 times under comparable survey conditions. Actual productivity depends on survey design, electrode layout, terrain, contact resistance, power conditions, and field logistics.

Depending on the selected configuration and cabling layout, the GD-20 can support 2D resistivity or IP profiling, as well as 3D survey workflows. These capabilities can help investigation teams collect electrical-resistivity data across larger or more complex sites before selecting priority locations for direct verification.

Oil Pollution Investigation at a Chemical Factory Site

In a documented chemical-factory oil-pollution investigation, Geomative used a Wenner-Schlumberger ERT array to investigate the distribution of subsurface electrical anomalies associated with suspected oil pollution.

The project covered an approximately 4,000 m² survey area and used six ERT survey lines with 1 m electrode spacing. According to the reported interpretation, the average depth of the pollution-related anomaly was approximately 3–7 m; the deepest interpreted anomaly was approximately 12 m, while the most severe interpreted zone was approximately 4–6 m deep. The reported pollution-distribution area was approximately 1,287 m².

These findings provided a spatial reference for subsequent environmental investigation. As with other ERT applications, the interpreted anomaly should be verified through appropriate drilling, sampling, laboratory testing, and site-specific technical assessment.

From Periodic Surveys to Long-Term Data Observation

A one-time ERT survey provides a snapshot of subsurface electrical conditions. Some contaminated sites, landfill facilities, dams, and environmental remediation projects may also require repeated surveys or ongoing observation of selected indicators.

According to Geomative’s latest product information, the Geomative Online Monitoring System combines on-site monitoring equipment, cloud data transmission, and data-analysis functions. It supports real-time online monitoring, data inversion and display, configurable alarm thresholds, and alerts through channels such as SMS, WeChat, email, and sound-light devices.

Its published application directions include landfill leakage monitoring, tailings pond or dam safety monitoring, and groundwater-migration monitoring at contaminated sites. Site-specific system design, sensor selection, power supply, communications, maintenance, manual inspection, and verification procedures remain necessary for any long-term monitoring project.

A Practical Investigation Workflow

A soil-contamination investigation can follow a staged workflow:

1. Review site history, production records, pipe and tank layouts, geological information, and existing sampling data.

2. Conduct a site walkover and identify areas requiring priority investigation.

3. Use ERT and other suitable geophysical methods to map subsurface electrical or structural anomalies.

4. Combine geophysical interpretation with soil and groundwater sampling plans.

5. Verify priority anomalies through drilling, sampling, laboratory testing, and engineering assessment.

6. Establish repeat-survey or online-monitoring plans where long-term risk management is required.

7. Maintain traceable records of field data, survey layouts, interpretation results, verification outcomes, and follow-up actions.

Conclusion

ERT can provide valuable spatial context for soil contamination investigation by helping teams identify and prioritize subsurface electrical anomalies. Geomative’s GD-20 multi-channel system can support efficient field acquisition for resistivity and IP survey workflows, while the Geomative Online Monitoring System can support continuous data observation in suitable long-term monitoring scenarios.

For environmental projects, the strongest decisions come from combining geophysical survey results with direct sampling, laboratory analysis, geological interpretation, and site-specific risk management.

https://www.geomative.com
Geomative Co., Ltd.

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