Remediation works involving the E-Clay stabilisation of contaminated soil arising to enable reuse back onsite as fill during the enabling works for 4 new wind turbines at the Port of Tilbury
Site Background & History
The Port of Tilbury as part of their “continued drive to achieve sustainable clean environmental solutions ” planned to install four new wind turbines in 2013 at the Port of Tilbury.
The new 2.3MW, 80 metre turbines will operate continuously and provide up to 60% of the ports electricity needs for the Port.
The Port of Tilbury installed four wind turbines in 2013. These 2.3MW, 80 metre turbines operate continuously and provide up to 60% of the ports electricity needs.
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 Materials Management Plan for the enabling works indicated a net surplus of soils (generated by the need to install the piled foundations for the turbine bases / pads within the made ground).
A waste assessment indicated it was shown that the soils were a mixture of inert, non-hazardous and hazardous (H14 ecotoxic). The identified contaminants of concern were heavy metals (particularly copper, lead and zinc, polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPH).
The original proposal for the enabling works was for offsite disposal of all surplus soils and import of clean infill materials around the foundation. However based envisaged costs associated with the offsite disposal of hazardous soils, Balfour Beatty implemented a more cost-effective and sustainable remediation solution. The agreed remediation strategy involved the treatment of surplus soils to enable reuse on-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 E-Clay Stabilisation. This was designed to treat both heavy metal and organic PAH / TPH contamination within the made ground as previously identified.
The contaminated soils were treated ex-situ utilising the designated E-Clay Stabilisation formulation. The soils were treated in batches utilising a mixing bin. The treatment process involved mixing the soils with the designated E-Clay formulation in slurry form and cementitious materials. The soils were mixed with the treatment materials to produce a homogeneous mass.
Representative composite samples of treated soils were leach tested and compared with the derived leachate target criteria. A total of six samples were tested and all leachate values were compliant with the designated remediation criteria. The treated material was therefore
considered suitable for reuse on site as a substitute for imported fill.