Case Study: Cardiff Waste Water Treatment Works

This project entailed the construction of the largest waste water treatment works and associated infrastructure in Europe. The £180 million scheme provides an additional link in Dwr Cymru’s programme of water treatment services and environmental improvements around the principality. The works themselves include a 10km tunnelled sewerage link connection across the Wentloog Flats, which diverted existing outfalls into the process works. The process of treatment involves a system of SBR [Sequential Batch Reactor] tanks in which sewerage is treated by means of a bacterial process before the treated cleaned water is pumped out to sea and the remaining waste sludge is treated by a centrifuge and drying process before transport off site for use in other industries.

The project was constructed on a heavily contaminated site which involved substantial land reclamation including excavation to suitable level to allow placing of till to raise to formation level for construction and formation of an "elevated" conservation area, using excavated material and removal during excavation of "contaminated fluc dust" (a by-product of the steel industry dumped on the site in previous years). This material required specialist disposal at sites in Swindon and Pontardawe. ChandlerKBS provided a full cost management service from inception through to the settlement of the final account.

The scheme was significant for being the first partnering scheme of the AMP2 period that DCWW embarked on with all ChandlerKBS staff working in an environment that actively discouraged the traditional adversarial approach to cost management.

Financially, the scheme was a significant success with out-turn costs within the £180 million budget.