A couple of weeks back the two cutting heads that will drill the new super sewer under London were shown off in a public open day.
It was basically a chance to walk around the giant machines and ask questions. The huge shaft next door where they will be dropped down 17 storeys to the bottom was… not part of the open day.
The two cutting heads are also different, as one will be heading through more chalky ground while the other will cut through clay.
Shortly, one cutting head will be lowered down to the drilling level and pushed into a pre-dug tunnel, and then each of the sections needed to power the TBM and its facilities will be lowered down after it.
To put the size into context – the Thames Tideway tunnel diameters will be 7.2 meters, compared to 6.2 metres for the Elizabeth line/Crossrail and an average of 3.6 metres for the London Underground tube tunnels.