Project: Remediation of Coal Tar in a Manufactured Gas Plant Gasholder


North Adams, MA


Coal tar, naphthalene, benzene, and TPH


2,200 cy


Reduce concentrations of VOC, SVOCs, and TPH below MCP UCL limits

Number of Heaters


Mass Removed

139,877 lbs.

Important Project Details

Approach: Prior to the site being heated, coal tar DNAPL had resisted recovery. After dewatering, TCH was applied in a step-wise fashion, without excavation. To our knowledge, this is the first site where a multi-level in situ heating approach was ever applied. We utilized three levels of heating (Levels 1, 2, and 3) sequentially, achieving low (80°C), moderate (100°C), and higher (325°C) soil temperatures, respectively.

Challenges: A total of approximately 140,000 lbs of mass was removed from the relatively small gasholder, and as a result of the material removal, the soil in the holder subsided. The subsidence damaged the insulated vapor cover constructed over the treatment zone.

Results: Guaranteed performance contract was signed to achieve a permanent solution in accordance with the Massachusetts Contingency Plan (MCP), by eliminating DNAPL within the holder and reducing concentrations of VOCs, SVOCs, and TPH below MCP upper concentration limits so that residual risk is minimized. All remedial goals were met.

What Makes this Project Unique

On Site, an abandoned gasholder contained approximately 2,200 cy of soil and debris contaminated with coal tar. The 62 ft diameter by 18 ft deep gasholder had brick walls and a bottom believed to be constructed of concrete. TerraTherm used our high temperature TCH approach to perform a multi-level in situ heating approach.

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