Hammersmith excavation complete

Excavation work on the interception chamber at Hammersmith Pumping Station site for London's super sewer has been finished successfully.  

Excavating a 20 metre deep chamber, 25 metre by 15 metre in any circumstances can be challenging at the best of times. But when that excavation is directly alongside an existing asset through which over two million tonnes of stormwater flows every year, it complicates things even further.

That was the challenge facing the team at Hammersmith when they were tasked with creating a new interception chamber. The existing inlet channel was built in the 1960s, and its design was smaller than would be desirable on a project of this scale. Extreme caution was required to safeguard it during the excavation works, and much planning was required to ensure the ideal outcome.

In fact, prior to excavation commencing, project workers spent over 18 months carrying out analysis to ascertain the likely effects of the dig.

Works started in August 2017, and the final bucket of London Clay was removed in September of this year. 

Alongside the works on the interception chamber, a tunnel the length of three football pitches has also been dug under Hammersmith to help tackle sewage pollution in the River Thames.

The 300m-long connection tunnel between Hammersmith Pumping Station and the middle of the River Thames will eventually connect into the 25km Thames Tideway Tunnel, under construction to tackle sewage overflows from London’s Victorian sewers.

Hammersmith Pumping Station currently spills around a million tonnes of untreated sewage into the Thames each year on average, making it one of the most polluting overflow points along the River Thames.