Commercial development had taken place over the infrastructure remaining from a former gas works site, remnant coal tar contamination was present in underground gas holder bases. Extensive stakeholder engagement established project parameters and constraints, including the requirement to maintain safe access at all times. The remediation design incorporated de-watering of gas holder bases with waters treated via a sludge reactor to reduce ammonia concentrations. NAPLs were recovered by multi-phase extraction, with stabilisation / solidification applied to the remaining contents. The project subsequently won an extensive suite of awards.
Site validation criteria included the removal of mobile contaminants in the form of LNAPLs and DNAPLs; removal of shallow tarry materials, spent oxide, foul lime and carbon black; and stabilisation solidification of wastes within gas holder bases to meet site specific criteria for a wide range of coal tar related compounds.