With a target of 100% reuse of contaminated materials, contractor Land & Water has set the bar high for its remediation of material excavated at a disused shipyard at Brightlingsea, Essex.
Developer Hampstead Homes is to build new apartments, a carpark and a marina around the existing docks.
The £25M scheme involves excavating 20,000m 3 of material, 12,000m 3 of which is contaminated with lead, zinc, copper and fuel. Soil washing is being used so the ground can be reused on site for the creation of inter-tidal marshes to replace those lost to sea level rise and changing land uses. Much of the material will be placed below the high water mark, requiring it to be squeaky clean.
The end product of soil washing is a 'cake' of concentrated contaminants mixed with a small quantity of uncleanable material.
Cement is mixed with the cake to form solid blocks from which the nasties cannot escape. These are being used for landscaping above the high tidemark.
The Environment Agency has insisted that quality assurance analysis is carried out for every 500m 3 of material reused, says Land & Water director James Maclean. 'It's been quite onerous, ' he admits, 'but we have effectively provided complete traceability of all materials throughout the process.'