Cliffe supplying ballast for Thames Tideway

Brett Aggregates supplying 150,000 tonnes of ballast as dredged for construction of temporary cofferdams

BRETT are to supply 150,000 tonnes of marine-dredged ballast aggregate to the £4.2 billion Thames Tideway Tunnel project through FLO, a joint venture of Ferrovial Agroman UK Ltd and Laing O'Rourke Construction, who are the main contractors for the central section of the project known as Tideway Central.

Thames Tideway Tunnel, the biggest infrastructure project ever undertaken by the UK water industry, aims to upgrade London’s sewerage system to cope with the demands of the city well into the 22nd century.

Victorian sewers, built in the 1860s, still form the backbone of London’s sewerage system today but were not built to cope with the capital’s current population level which, at more than 8 million, has increased four-fold since their construction.

Overflows designed to discharge once or twice a year now do so almost weekly, pouring tens of millions of tonnes of untreated sewage into the river Thames each year causing high levels of pollution.

The project will see a new 25km interception, storage and transfer tunnel, running up to 66m below the Thames, into which overflows will be diverted, taking them away from the river.

Six gigantic tunnel boring machines (TBMs), which will be lowered underground via shafts to be constructed at various sites along the route, will be used to excavate the tunnel.

During 2018, Brett will supply 150,000 tonnes of ballast as dredged (BAD) for the construction of temporary cofferdams at five shaft sites in the Tideway Central section of the project, namely, Blackfriars, Victoria Embankment, Chelsea Embankment, Albert Embankment and Heathwall Pumping Station.

Delivered by barge from the company’s Cliffe site, the aggregate will form the core of the cofferdams to be built in these locations. Each cofferdam will create a watertight enclosure that will be pumped dry so that construction can proceed under normal conditions.

‘Bringing material in by barge has many benefits for both the environment and the community,’ said Tim Smith, commercial director at Brett Aggregates.

‘Our Cliffe site is ideally placed and equipped to supply the required volumes using this low-carbon method of transportation and the aggregate we deliver has been dredged from our licensed sites offshore. Reducing truck movements is particularly important in London where congestion and pollution are significant issues.’

Once the Thames Tideway Tunnel has been completed in around five years’ time, the cofferdams will be deconstructed and the aggregate supplied by Brett will be returned to Cliffe for reprocessing into useable aggregate for re-sale and use in other construction projects.