A meticulous maritime operation on the Thames has signalled the start of construction work for the £4.2 billion Thames Tideway Tunnel.

Two boats - 'Shake Dog' and 'Bull Dog' – have now pushed a barge supporting a crane into position near Blackfriars Bridge, to allow work to start on a new pier in preparation for construction of the long-awaited super sewer.

The 25km tunnel is intended to tackle pollution of the tens of millions of tonnes of sewage overflowing into the tidal River Thames every year.

Andy Alder, Central Project Delivery Manager for Tideway, said:

"Getting the barge into place was no mean feat. The 20m wide barge had to be carefully threaded under seven bridges and through the traffic on one of the busiest working rivers in the world. Alongside the man-made challenges, the crane also needed perfect tidal water levels and good weather before the movement could go ahead.

"This crane will give us the capability that we need to prepare the Blackfriars site for our vital work to upgrade London's sewerage system.

"This work is taking place directly next to one of Sir Joseph Bazalgette's famous interceptor sewers in the embankment, so it’s a fitting place to start our work."

The new pier for Thames Clippers users will be built to the eastern side of Blackfriars Railway Bridge, and is due to come into use later next year.

The work, which is being undertaken by VolkerStevin for Tideway, will also include building a new staircase and lift connecting the Embankment and Blackfriars Bridge.

During construction, Tideway is aiming to transport 90% of spoil from the main tunnel by river, drastically cutting down on the number of lorry trips that would otherwise be needed.

Two weeks ago Tideway received three certificates from BSI, the business standards company, for its business management system.

Following an audit in October, BSI has awarded certification to Tideway's management systems in accordance with Quality Management (ISO 9001), Environmental Management (ISO 14001) and Occupational Health and Safety (OHSAS 18001).

The certificates were awarded following an independent assessment of Tideway's Programme Integrated Management Systems (PIMS), which defines the processes and systems in place to deliver the Thames Tideway Tunnel.

Mark Sneesby, Tideway's Chief Operating Officer, said:

"This is a huge achievement for Tideway and reflective of the effort put in by employees across the company. It demonstrates our dedication to making sure we do things properly at Tideway, and being a leading example of how infrastructure projects should operate.

"We are setting an example to our supply chain by gaining and maintaining certification to all three standards. It is a requirement for our Main Works Contractors and System Integrator to also gain management system certification."