The Thames Tideway Tunnel Scheme is a 25km long tunnel underneath the River Thames running from East to West London. London relies on a 150 years old sewage system built for a population currently half its size, as a result millions of tons of raw sewage spills untreated into the River Thames every year. Active Tunnelling are sinking 2no shafts on a very tight site to help create this legacy for future generations.
The shafts are constructed using 3 different forms of shaft sinking, Caisson, underpinned and Spray concrete lining. The large shaft is new CSO 17.5m ID and will be sunk to a depth of 54m BGL, the smaller shaft is an Interception shaft 11.5m ID sunk to a depth of 24m BGL. The interception shaft will capture the sewage before it discharges into the Thames and transfer it via a 2.4m ID tunnel into the new CSO prior to discharging through a 4m ID connection tunnel that will connect to the main tunnel below the River. The biggest challenge to the scheme is getting deliveries into site due to its Central London location, with large plant not allowed within the M25 before 7pm the logistics are proving to be the biggest challenge of the scheme. With both shafts positioned on a very tight site with close proximity to the River and surrounding high rise apartments the scheme has to be carefully managed to prevent disruption to residents. The muck from the shafts is being transferred via River barge to reduce the carbon footprint of the works and is proving to be a very cost effective and efficient form of transportation.
Active Tunnelling are very pleased to be part of such an immense civil engineering project and the legacy of leaving a clean river for future generations to enjoy is one we are very proud of.