The joint venture of Costain, VINCI Construction Grands Projets and Bachy Soletanche, which is working on the east section of the Thames Tideway Tunnel, has been awarded the Brownfield Redevelopment Project of the Year trophy at the Ground Engineering Awards 2019.
At the Earl Pumping Station in Lewisham, the project required an innovative solution to successfully deliver the ground engineering element. One of the significant risks associated with the construction works at this site is the presence of in-ground hydrocarbon contamination. To facilitate construction of the 60-m deep diaphragm wall shaft, the joint venture opted to utilize cutter soil mixing technology to mitigate the risk of identified contaminants entering the chalk aquifer via the diaphragm walling process.
The innovative aspect of this work was the use of the cutter soil mixing to form a safe zone through which to telescope the diaphragm wall shaft, similar to the approach a ground improvement contractor would adopt if undertaking ‘clean drilling’ methods. This is the first time such a method has been successfully used on a UK construction site.
In addition to the technical complexities, working within the contaminated ground required a significant consenting process under the Development Consent Order to get the remediation strategy in place, through engagement with the Environment Agency and the Local Authority.
Commenting on the success, Tideway’s Deputy Delivery Manager, Maurice Gallagher, said: “When the joint venture tendered for this project back in 2014 the extent of the contamination and the risk of drawing this down to the underlying aquifer on the Earl Pumping Station site was a key challenge for us at Tideway. It is fantastic to report, some four years later, that the shaft diaphragm walling has been completed without issue on this highly constrained site under intense scrutiny. The team fully deserve recognition for the skill, professionalism and care that they have demonstrated in undertaking these complex works.”
Martin Stanley, Geotechnical Manager added: “It is a privilege for our project to be recognized with this award. The collaborative approach between the joint venture and its partners ensured the project was successfully delivered ahead of schedule, whilst mitigating the risk of contamination.”
In winning the award, the Costain, VINCI Construction Grands Projets and Bachy Soletanche JV acknowledges the support from a number of other parties in the successful delivery of these works, including PMC Soil Solutions, Atkins, Soiltech Belgium and RSK RemedX.