Site Background & History
The Port of Tilbury plans to build four wind turbines on the southern riverfront of the port adjacent to the River Thames. Balfour Beatty was commissioned to undertake the enabling works as part of this development.
The majority of the site area is recovered marshland which has been infilled with imported materials (to enable the site to be suitable for development and to raise site levels). The resulting made ground on the surface is generally 2 – 3m in thickness.
A Soil Management Plan for the enabling works indicated a net surplus of soils (generated by the need to install the foundations for the turbine bases / pads within the made ground).
Based on the assumption that the surplus soils would be removed from site and disposed of at a suitable landfill a Waste Classification Assessment was carried out in 2012 by RSK to determine the likely waste classification of surplus materials generated from each of the four turbine installation areas. It was determined that the soils were a mixture of inert, non-hazardous and hazardous – the hazardous classification was determined on the basis of H14 exotoxicity. The identified contaminants of concern were heavy metals (particularly copper, lead and zinc, polycyclic aromatic hydrocarbons [PAHs] and total petroleum hydrocarbons [TPH].
Balfour Beatty subsequently decided to implement a more cost-effective and sustainable remediation solution for the turbine development project. The agreed remediation strategy was to treat surplus soils classified as hazardous / non-hazardous for reuse on-site and only remove from site soils classified as inert (in accordance with the soil management plan for the site).
The remediation strategy was developed and agreed with the Environment Agency. A Remediation Method Statement was produced by Envirotreat to document the proposed works and remediation objectives.
The treatment technology utilised in the remediation process was Advanced (E-Clay) Stabilisation. This was designed to treat both heavy metal and organic PAH / TPH contamination within the made ground as previously identified.