A year after it first got under way, the first major work for London's Thames Tideway Tunnel "super sewer" project has been completed. A replacement pier at Blackfriars will provide continued access to river transport during work to reinforce the nearby river wall.

To construct the pier, six piles measuring 31-m (102-ft) long and weighing more than 40 tonnes (44 tons) each were transported by sea from Italy. These were lifted using a floating crane and driven up to 23 m (75 ft) into the riverbed. The 84-m (276-ft) long, 700-tonne (772-ton) pier, which was towed by sea from the Netherlands, was then lifted onto the piles.

The whole process, of course, had to be carried out on the Thames itself, meaning the construction team had to deal with the river's challenging conditions, such as the constant ebb and flow of the tide. The completed pier, however, is able to berth two boats at once, rather than just one, allowing for greater passenger capacity than the pier it has replaced. It will be used by over 50,000 people a year.

"The new pier at Blackfriars is the first physical clue of our work to build the Thames Tideway Tunnel in the heart of the City of London," says Tideway delivery manager Andy Alder. "This was a huge task with many challenges, including coordinating the arrival of materials from Holland and Italy by sea, building in the river alongside changing tides and working safely around the weather."

The 25-km (16-mi) long super sewer tunnel is being built to reduce sewage overflow into the Thames and to accommodate the amount of sewage produced by London's growing population. The city's current sewage system is largely Victorian and was not built to handle a population of the its current size or the increased level of rainwater run-off caused by it being increasingly built-up.

When there is heavy rain and the system becomes over capacity, Combined Sewage Overflow (CSO) points discharge excess sewage into the river to avoid streets and homes flooding. Over 39,500,000 cu m (1,400,000,000 cu ft) of sewage is said to be emptied into the River Thames via the CSOs each year, with the Thames Tideway Tunnel aimed at reducing this to around 2,400,000 cu m (84,800,000 cu ft).

The tunnel will link the 34 most polluting CSOs, siphoning away sewage that would otherwise have been directed into the river. The system will also be able to store up to 1,600,000 cu m (56,500,000 cu ft) of sewage until it can be treated.

Construction of the pier began in November last year. The first boat docked at it on the morning of October 31 this year, but it was officially opened on December 1. Tunneling activity is due to begin next year and to be completed by 2021, with the tunnel expected to be fully complete by 2023.

The video below provides an overview of the pier project.

Source: Tideway