The site included three large gas holders and extensive legacy infrastructure, bringing with it significant risks to groundwater, human health and the surrounding environment. Our role was to safely dismantle, remediate, and prepare the land for residential redevelopment while maximising sustainability and material reuse.

Here’s what our team delivered:

• Excavation, screening and segregation of 85,000m3 of soil
• Ex-situ bioremediation and chemical oxidation of 30,000m3 hydrocarbon contaminated soil
• Demolition of remnant gas holder structures and bases (above and below ground)
• Dewatering and sludge removal
• Installation of temporary sheet piles and monitoring boreholes
• Pumping and treatment of groundwater using extraction wells and disposal of treated effluent to sewer
• Use of sump pumps and localised well pointing to control groundwater
• Oxygenating chemicals injected into soils beneath site
• Flooding of shallow trenches around the edge of the gasholders using biomix to treat hydrocarbon contaminated soils in situ (6-8 weeks before excavating the material and processing it prior to off-site disposal)
• Groundwater treatment to remove NAPL
• Stabilisation and formation of piling mats
• Environmental monitoring to ensure minimum impact from vibration, odours and dust
• Validation reporting to regulators

The site was transformed safely, sustainably and efficiently paving the way for Berkeley Homes to deliver the Queenshurst apartment community now thriving in Kingston-upon-Thames.

At Cognition, we specialise in turning complex environmental challenges into development opportunities and removing risk in the ground for our clients. If you’re looking for a partner to help unlock contaminated or constrained land, please get in touch.