A Victorian era sewer running over the top of Baker Street tube station is currently being repaired even as it still carries away our daily waste.
The Kings Scholar Pond sewer, buried 2.1 metres underneath the junction of Baker Street and Marylebone Road, but on top of the Hammersmith and City line, was found to be in need of repair during a routine inspection.
The £20 million pound project aims to extend the life of the sewer by more 100 years and avoid travel disruption caused by it flooding into the tube station below.
The project requires a stainless steel bridge and liner to be constructed off site, dismantled and then rebuilt inside the sewer, after being lowered underground, a single piece at a time through a narrow manhole.
Asad Hanfi, Thames Water project manager, said: “This is one our most challenging sewer repairs ever. We’re taking the pieces of a giant 3D jigsaw underground through a hole no wider than the wheel of a van, and piecing it all together to reinforce the existing brickwork and improve the resilience of the sewer for more than another century.
All that can be seen from above ground is three small fenced off areas of pavement to allow access through the manhole and store equipment.
Underground, in addition to the steel structure, the team has inserted a reinforced resin liner to strengthen the sewer for around 120 years. The steel structure has been designed to not require maintenance for the duration of that period while the liner can be removed a panel at a time to allow the original Bazalgette brickwork to be inspected as normal.
During the project, which is due to run into early next year, wastewater flows are being carefully managed, with a system of cameras and alarms used to alert teams to evacuate if necessary, as the sewer is used to carry overflows from neighbouring tunnels during periods of heavy rain.