Prichard’s were appointed as Principal Contractor to carry out the remediation and restoration works of Dow Silicones landfill site in Barry. The project was overseen by CQA engineers AECOM and had a daily site visit from Dow.
The works involved the clearance of site vegetation and the re-profiling of over 25,000m3 of existing works wastes and contaminated material. This material was hydrophobic in nature and very difficult to deal with when wet. The material was highly contaminated and due to the high groundwater levels across the site the team setup a pumping system with silt busters before the water was discharged into Dow’s treatment plant to drain the site.
The material was eventually dried out in windrows across the site before it was able to be mixed with stabilisation materials and worked with to be compacted in place using a GPS dozer system to achieve the formation levels ready for the capping.
Adjacent to the site is a former Timber Pond and ecological habitat monitored by AECOM and Natural resources Wales, to prevent any water or contaminants from entering into the pond a stone bund was constructed at the start of the remediation works and was removed piecemeal as the lining and capping works progressed, this process underwent a watching brief by AECOM to ensure the Timber Pond was kept clean.
The capping works included the import of over 70,000 tonnes of clean capping soils, meeting a strict chemical and geotechnical criteria to be placed in a 300mm thick regulation layer before the GCL Plastic backed liner was laid across the site by Prichard’s with another 300mm layer of regulation soils and 150mm of restoration soils laid across the surface. This soil was carefully placed on the site to ensure there were suitable roadways constructed for the dump trucks to safely travel on above the liner.
The project also included a drainage channel, manhole, several headwalls and a road crossing to catch the surface water from the remediated capping and divert it from the site and through a culverted crossing into Dow’s wetlands and environmental habitat.
A timber edge subbase footpath was constructed along one side of the capping to allow future access to borehole monitoring points and a tarmac apron was constructed around the opposite side as a new footpath for the works personnel.
The project was successfully completed within the clients budget and in line with Natural Resources Wales’ programme and completion dates.