Manufactured Gas Plant Site Remediation - Oil, Gas & Refineries

It is estimated that there are over 3,000 former Manufactured Gas Plant (MGP) sites across the United States. Another 4,000 dot the landscape of Canada, the UK, continental Europe and Japan. These sites were built long ago on rivers or harbors, often on the outskirts of towns and cities; locations that are now frequently in close proximity to infrastructure, buildings and residential areas. Many underlie or abut valuable commercial, residential, and municipal properties, posing environmental hazards to ground and surface waters. The urgency of remediation has increased due to a potent blend of community activism, regulatory pressure, high real estate values, and the need to reduce liability in light of the Sarbanes-Oxley Act and other measures.

TerraTherm’s in situ thermal remediation technologies offer you several advantages for the remediation of your MGP sites:

  • Achieve your cleanup goals, even to residential standards;
  • Obtain excellent ROI, eliminate liability and increase your property value;
  • Remove mobile volatile organic compounds, such as benzene and naphthalene that often drive site risk;
  • Permanently stabilize and immobilize the remaining coal tar as non-leachable material resembling asphalt;
  • Prevent migration beyond property boundaries, and protect water bodies;
  • Allow ongoing commercial activities on site;
  • Applicable beneath buildings and near structures such as roads and bridges, and where other physical features cannot be disturbed;
  • Work above and below the water table;
  • Applicable to many soils including silty clay layers and heterogeneous soils with wide variations in permeability and water content, and in fractured rock; and
  • Significantly reduce long-term operations and maintenance costs of traditional pump and treat systems.

The ISTS Process
Terra Therm's approach to the remediation of MGP sites includes In Situ Thermochemical Solidification (ISTS) of coal tar. ISTS works by:

  • Raising the subsurface temperature to at or slightly above the boiling point of water;
  • Distilling off volatile organic compounds (benzene, naphthalene) for vapor recovery; and,
  • Leaving residual coal tar constituents within a solid, stable mass (resembling asphalt) that will not leach or migrate.

Note that the ubiquitous asphalt in our roads and highways similarly contains PAH compounds, but they are not considered an environmental or human health risk because they are not leachable or mobile.


After ISTS treatment, contaminated residual tar remains in the soil, but has physical properties like asphalt. This transformation eliminates the environmental risk of coal tar migration. It’s a permanent, effective solution.

Before treatment (left), liquid coal tar coats an auger plug. After treatment (right), thermally stabilized coal tar heated to 110ºC has the consistency of asphalt.