Cognition was contracted to carry out remediation works at Kingston Gasworks, prior to the construction of luxury residential apartments and a large basement car park. The site contained three large gas holders, together with associated infrastructure and small buildings. The soils and groundwater were contaminated with hydrocarbons, heavy metals and cyanide. Japanese Knotweed (an invasive, non-native plant) was also present. Cognition was approached at an early stage of development and reviewed the strategy to ensure the remediation approach was cost effective and sustainable.

Cognition carried out demolition of the former gas holders and the installation of deep and shallow sheet piles, to temporarily cut off groundwater and enable excavation for the basement. Cognition also dug out and disposed of soils impacted by Japanese Knotweed. Groundwater was pumped into a treatment plant and the treated water discharged to the sewer under a permit from Thames Water. Cognition developed a materials management plan which enabled contaminated soils to remain on site (encapsulated within clay beneath the basement), thereby substantially minimising disposal costs. Cognition also stabilised site-won soils for the formation of piling mats.