Below Ground Tar Tank

Wigan

The Problem

Biogenie Remediation UK Limited were invited by National Grid to remediate a below-ground tar tank that had been uncovered as part of groundworks on a former gasworks site in the northwest of England.

The tank was located between two and six metres below the existing ground level and contained ~1.5 metres of viscous coal tar at its base. The combination of the tank location, a live 24” above-ground gas main, and site boundaries that were in very close proximity to the tank edges, meant that traditional opening and excavation of the tank was not an option.

At the commencement of the remediation, the full extent of the tank was unknown, and the client was concerned it might extend beneath critical infrastructure and adjacent 3rd party property.

The Solution

To gain clarity, we partnered with Nationwide Drones to carry out a LiDAR drone survey (click to view), providing precise data on the tank’s footprint, giving our client much-needed assurance and volumetric estimates of the tar within the tank.

Pilot trials revealed that conventional pumping methods would be ineffective and the Biogenie team designed and delivered a solution applying controlled heating, that reduced the tar’s viscosity making it pumpable.

Using a closed-loop heating system, we successfully raised the temperature of the tar from 11°C up to 38°C, enabling its recovery via specialist pumps.

The Result

242 tonnes of tar safely recovered.
No impact on gas infrastructure or site boundaries.
Final drone survey confirmed the tank’s integrity and allowed safe decommissioning.

Following the tar recovery, the tank was infilled with specialist Cemex Porofoam, a lightweight foamed concrete developed for complex and confined locations where the use of traditional fill materials is impractical. The project will enable a new lease of life for this part of the former gasworks as part of future development.

This project is a great example of Biogenie’s commitment to innovation, safety, and collaboration, combining smart technology, thermal recovery expertise, and precise execution to solve complex environmental challenges.

A big thank you to our project team and partners at Nationwide Drones for their exceptional work.