Electrical Resistance Heating (ERH)
The workhorse of in situ thermal remediation: ERH turns the soil itself into the heater, boiling chlorinated solvents and VOCs out of the ground — even in tight clays where nothing else works.
How ERH Works
Electrodes are installed in a grid across the treatment zone. When electric current flows between them, the natural resistance of the soil converts that energy into heat — exactly like the element of an electric heater, but underground.
As the subsurface approaches the boiling point of water, two things happen: contaminants with low boiling points volatilize, and in situ steam is generated that strips contaminants from soil pores and groundwater. A network of vapor recovery wells captures the steam and contaminant vapors under vacuum, and an on-surface treatment system condenses and destroys the contaminants before clean air is discharged.
The process, step by step
- 1. Wellfield installation — electrodes, vapor recovery wells and temperature monitoring points are drilled on a grid designed by thermal modeling.
- 2. Power application — current is applied in controlled phases; subsurface temperature is tracked in real time at dozens of points.
- 3. Volatilization & steam stripping — contaminants transfer from soil and groundwater into the vapor phase.
- 4. Capture & treatment — vacuum extraction collects vapors for condensation and treatment at the surface.
- 5. Confirmation sampling — soil and groundwater samples verify that cleanup criteria are met before demobilization.
When ERH Is the Right Choice
- Chlorinated solvent source zones — TCE, PCE, TCA, DCE, vinyl chloride
- DNAPL trapped in silts, clays and low-permeability layers
- Contamination beneath operating buildings, where excavation is impossible
- Saturated-zone treatment — ERH heats groundwater and soil together
- Urban and space-constrained sites that need a small surface footprint
Why Project Managers Choose ERH
Works where others fail
Heat conducts through clay just as well as sand — no reliance on injecting or pumping fluids through tight soils.
Predictable schedule
Energy delivered translates directly into temperature and mass removal. Timelines are engineering, not hope.
No excavation
Treatment happens in place, under buildings and infrastructure, while your facility keeps operating.
Verifiable in real time
Continuous temperature and vapor monitoring shows progress week by week — you see the mass coming out.
Fast site closure
Months of heating typically replaces decades of pump-and-treat operating costs and liability.
Combines with other remedies
Low-temperature ERH also accelerates bioremediation and chemical reduction as a polishing step.
ERH — Frequently Asked Questions
How hot does ERH get the subsurface?
Up to the boiling point of water — around 100 °C. That is enough to volatilize chlorinated solvents and other VOCs, which are then captured by the vapor recovery system.
How long does an ERH remediation take?
Most projects reach cleanup goals within months of active heating, depending on treatment volume, contaminant mass and geology — dramatically faster than pump-and-treat or natural attenuation.
Can ERH operate under an active facility?
Yes. Electrodes and recovery wells have a small footprint and can be installed through floors and around operations. Production typically continues throughout treatment.
Is ERH safe?
ERH systems are engineered with strict electrical safety controls, continuous monitoring and automatic interlocks. The technology has decades of safe operating history worldwide.
Have a Chlorinated Solvent Site?
Send us your data and our engineers will tell you — honestly — whether ERH fits, what it would take, and how long it would run.
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