Value: £5.6 million
Basford was chosen by National Grid to trial the first large scale soil washing project in the UK.
Approximately 120,000 tonnes of predominantly granular fills and contaminated sands and gravel were treated by soil washing to produce clean fill material for re-use on site.
The project required the excavation of 150,000m³ of material of which 70,000m³ was contaminated by coal tars and liquors, hydrocarbons, sulphates and cyanide and dealt with by soil washing. Other works undertaken included selective digging, ash recovery, tarmac recycling, crushing, screening, off-site disposal of special wastes and the import of suitable clean material. Ground investigation works and final site validation testing were also undertaken.
Much of the excavation on the 7ha site was undertaken at depths in excess of eight metres below the groundwater table and below geological rock-head. This required the continual pumping and management of considerate quantities of contaminated groundwater to an on-site water treatment plant for decontamination.