Sinclair Knight Merz has been involved in bringing a former steelworks site developable state for some years. The steel works was operational between the 1930’s and 1970’s. The area to be redeveloped included railway sidings, an ore storage area, a by-products plant, a coal stocking area and lagoons.
The site was on a former salt marsh adjacent to the Dee Estuary. The land was infilled with sand during the 1930’s to create land suitable for building on. Then in the 1980s, a reclamation scheme involving the removal of structures, visibly contaminated and unsuitable material was conducted.
The principal technical issues have been minimising the risks from pollution from the former coking by-products plant, which was part of the steelworks but outside the development area. An SKM investigation, using window sampling and on-site FID backed up by laboratory analysis showed that a plume of BTEX contamination straddled the site boundary. However, no agreement could be reached with the adjacent landowner regarding clean-up.
Ground water modelling commissioned by SKM also showed that the plume was unlikely to ingress further into the development site. The site was protected by the installation of a bentonite wall along the boundary between the two sites. Vents were excavated on the adjacent site, while contaminated soils on the development site were excavated and remediated on-site by bio-remediation.
A 650m long stone filled soak-away was also constructed to allow ground water recharge and to vent landfill gas that was being produced from a landfill along one of the site boundaries.