The small Middleton gas works site (0.4 hectares), borders the River Irk. The site was contaminated with pollutants including Total Petroleum Hydrocarbons (TPH), Polycyclic Aromatic Hydrocarbons, phenol and ammonium.
The overall remediation strategy was designed to address the contamination source and indirectly the pathway issues, with the intention of protecting both human health and groundwater receptors. The objective was to chemically stabilise the ‘contaminated’ soils using a E-Clay. The Envirotreat E-Clay process was selected based on a number of criteria, most importantly the ability to apply the E-Clay capability using an insitu approach. Logistical constraints prohibited the more conventional ex-situ approach being utilised in all areas across the site, however certain wastes were treated ex-situ.
The remediation strategy for the Middleton site comprised a two stage approach.
The first phase of the project involved the in-situ treatment of an area between the tar tank and one of the gasholders. The area identified was thought to have been impacted by tar leaking from an old storage tank. This stage involved the installation of approximately 200 overlapping soil-mixed columns, drilled to a depth of 8 metres (below ground level) in the contaminated area outside of the tar liquor tank.
The second phase involved more conventional ex-situ treatment of contaminated materials (gas works waste) taken from inside the tank.