‘Plunge pool’ under construction at Earl Pumping Station

Summer may be over, but a special ‘plunge pool’ has been created at Earl Pumping Station – although flipflops and swimwear are not on the agenda.

The 50 metre-deep shaft at Earl will connect the existing sewer network into the under-construction Greenwich Connection Tunnel, which will transfer sewage into the main super sewer at Chambers Wharf.

The shaft at Earl Pumping Station is an ‘online shaft’ – meaning it will drop directly into the Greenwich Connection Tunnel, instead of via a connection tunnel.

To facilitate the arrival of the Greenwich Connection Tunnel TBM Annie in the next few weeks, the shaft has been fully excavated and a base slab installed, before being partially backfilled with a temporary cement material into which the TBM will tunnel. Above this, the shaft has been filled with water to match the external water pressure of five bar.

Brooke Knight, project manager at Earl Pumping Station, said: “This is part of our preparation to welcome TBM Annie to Earl Pumping Station, as she digs the Greenwich Connection Tunnel. The 40 metre-deep pool of water will balance the ground pressure when TBM Annie tunnels underneath, allowing us to tunnel straight into the shaft.”

She added: “At tunnelling depth, the ground conditions in this part of London can be challenging because of the large flints and possible fissures in the chalk, so tunnelling and shaft excavation had required a huge amount of preparation.”

Earl Pumping Station is part of an existing Thames Water Pumping Station that has been in use for many years and will remain operational throughout our works.