Crowmarsh Gifford, Lister Wilder

The Challenge:

Cognition remediated an agricultural machinery yard in Crowmarsh, Oxfordshire which is to be redeveloped for residential housing. Large areas of the yard was built over foundry sand and clinker deposited on the site to raise the land and protect it from flooding. More than 13,000m3 was processed to remove contaminated waste. More than 60% of the material met the remediation targets and was re-used on site achieving significant cost savings on disposal and import of new materials Backfilling required careful re-profiling of the site to meet flood risk requirements including the creation of landscaped flood compensation areas bordering the River Thames. Cognition was also able to blend site won sand to create topsoil to cover a third of the 1.5 hectare site.

The key elements of these works included:

• Implementation of environmental monitoring plan to ensure minimal impact on site operatives and neighbouring residential developments;
• Demolition of buildings,  asbestos and underground storage tank removal ;
• Assisting Museum of London with archaeological excavations and surveys;
• Bioremediation of hydrocarbon impacted soils;
• Pre-processing (screening and hand-picking) of waste materials and oversize foundry glass and clinker;
• Testing of remaining material to determine residual level of heavy metal contamination and consider the material’s suitability for stabilisation;
• Soil material with higher concentrations of metals was designated to be backfilled beneath roads and hard standing areas under an MMP;
• Removal of Japanese knotweed and blending and production of clean capping soil for gardens within new development.