Much of the waste created by the works would be 'clean' (i.e. uncontaminated) materials, excavated from the river or from cut and cover excavations but surplus to requirements on the construction contract. It is known, however, that some of the surplus materials could be contaminated. Surplus materials dredged from the immersed tube tunnel trench may be disposed of at sea. This would fall under the strict control of the Department for the Environment, Food and Rural Affairs (DEFRA) from whom licences would need to be obtained. Alternatively, surplus river dredgings could be sent to licenced landfill sites in the region. If a licence were granted by DEFRA, approximately 140 000 m3 of unsuitable materials could be disposed of at sea. There are ongoing consultations between the TWPTA's advisors and DEFRA on this matter.

Approximately 160 000 m3 of sand and gravel would be dredged from the tunnel trench line and other construction areas. This may be temporarily stored adjacent to the river at the current RMC site at the former Mercantile Dockyard. Once the tunnel sections have been put in place approximately 150 000 m3 of sand and gravel would be used to refill the trench. The balance could be deployed elsewhere on the project or made available for sale on the open market.

The re-use of excavated aggregates within the construction project would reduce the need to bring in such construction materials from off-site. The excavation of the cut and cover trenches would also give rise to significant volumes of surplus material. Approximately 332 000 m3 of material would be excavated during these operations. Of this total, 167 000 m3 would be backfilled into the trenches, while the remainder (165 000 m3) would require disposal at a licenced landfill site. Landfill disposal of surplus excavated material would necessitate considerable haulage vehicle movements on the local road network.

General construction waste including concrete and mortar residues, packaging, damaged (unusable) materials and office wastes would be generated. In relation to the surplus excavated materials, the volume of construction waste would be very small. Opportunities for waste avoidance, re-use and recycling would be explored and implemented where practicable. Non-reusable construction waste would be sent off-site for disposal at a licenced landfill.

Contaminated Land

Some of the land that would be disturbed and excavated during construction has been contaminated by previous uses, such as industrial pollution and 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 would therefore be carefully managed in accordance with environmental and health and safety requirements. Strict health and safety procedures would be employed to prevent workers coming into contact with such material. Measures would also be taken to avoid the release of contaminants off-site, for example, through dust emissions. Contaminated material encountered within the construction area would be dealt with either on-site or disposed of off-site at a suitably licenced facility.

Contaminated material that can remain on-site would be deposited under waste licencing 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