Some of the land that will be disturbed and excavated during construction has been contaminated by previous uses, such as waste disposal. Some of the contamination is at a level which could, during construction, pose a potential risk to humans and the environment. Material identified as being contaminated will therefore be carefully managed in accordance with environmental and health and safety requirements.

Strict health and safety procedures will be employed to prevent workers coming into contact with such material. Measures will also be taken to avoid the release of contaminants off-site through, for example, dust emissions.

Contaminated material encountered within the construction area would be dealt with either on-site or disposed of off-site at a suitably licensed site. Contaminated material that can remain on-site would be deposited under waste licensing legislation strictly controlled by the Environment Agency, determined during detailed design. Any surplus material disposed of on-site would be deposited within carefully designed and constructed 'cells' that would not allow pollutants to escape.

The contaminated material could not, therefore, pose a risk to humans or areas of new landscaping. With contaminated material effectively sealed below the site once the new tunnel becomes operational, the scheme would not pose any long term ground contamination risk.