Mammoet’s Planning & Preparartion Aids Thames Tideway Project
Featured Title photograph Transportation of the TBM
Mammoet has safely lowered a 690 metric ton tunnel boring machine (TBM) down a 35- meter shaft in west London for the Thames Tideway Tunnel project. The ground-breaking project that aims to create a new ‘super sewer’ underneath the city of London is currently underway, with an expansive 25-kilometer network of tunnels under construction.
The new tunnels are designed to relieve pressure on the 150-year-old Victorian infrastructure that currently supports the city’s eight million citizens. When completed in 2024, the new system will prevent tens of millions of tonnes of pollution from entering the river Thames every year.
Mammoet devised a customized solution which allowed the project to be executed within the confines of inner-city London, where minor delays can cause major disruption. Overcoming complex regulatory constraints surrounding operator’s licenses for projects in central London and space restrictions that further complicated mobilization, Mammoet successfully lowered the TBM in half the average time – completing the lift in only one shift – ensuring drilling could commence on the scheduled date.
Situated within a highly congested and compact site in west London, lowering the TBM needed to be executed within the limited space available and with minimal disturbance to the surrounding area. Project Manager Maurice Janssen explains: “Working within a dense urban environment like this makes designing and mobilizing a suitable engineering solution more challenging. Given the populous surroundings, the project had to be completed within an acoustic shed, a metal structure designed to minimize noise pollution. So, Mammoet designed a tailor-made solution that would fit within these restricted dimensions while managing the limited ground bearing pressures. The final structure fit with only 250 millimeters clearing space to spare.”
Maurice continues: “With significant projects in busy cities like this, the level of disruption is high when something doesn’t go as planned. So, avoiding delays was of utmost importance to the client. We removed the risk of setbacks through a series of tests and detailed plans. The key equipment was pre-tested at our yard in Schiedam before it began its journey to London, to ensure there would be no unexpected problems when on site. The engineers were provided with an exceptionally detailed mobilization plan that factored in all possible risks of delays, making sure back up equipment was on standby throughout. This plan utilized Mammoet UK’s knowledge and experience of working in London, where safety procedures and regulations are some of the most stringent in all of Europe.”
This level of preparation combined with Mammoet UK’s local knowledge meant that, despite the challenges posed by a compact site in a dense urban setting, Mammoet could successfully mobilize and complete the build of the lowering system in just three weeks. Once this was in place, the TBM was lowered to the bottom of the 35-meter shaft in one ten-hour shift, keeping the project on schedule.
Mammoet has also been contracted to complete the lowering of two TBMs at Tideway East, the third and final phase of the project. The company is currently completing planning and securing permissions to prepare the transport route through central London. Work is set to begin in December 2019.
Lowering the 690t TBM into the shaft