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NETWORK / 20 / NOVEMBER 2018 PROJECT UPDATE A critical part of Cadent's work to future-proof London's gas infrastructure for the 21st century the Tunnel Under the Thames project has involved three of London's most fa- mous locations: the Royal Hospital Chelsea, Battersea Park and the River Thames. Engineers sunk a 30m deep sha„ at each of the land locations ahead of digging the 330m long tunnel using a micro tunnel boring machine (TBM). The tunnel houses a new gas main running under the River Thames. One of the key challenges for the project team has been stakeholder engagement. They liaised with 15 different organisations and secured almost 20 different permissions before getting the green light. The team also worked closely with Thames Tideway regarding their nearby Chelsea Foreshore works, to ensure both projects could pro - ceed together harmoniously. The project is being delivered by Ca- dent's strategic partner tRIIO, which also includes contractors Skanska, Morrison Util- ity Services and designers Mott Macdonald. "First off, we had to convince stakehold- ers of the need for the works," explains He- jdner. "We as the gas distribution business had a plan of what we wanted to do, how we wanted to reinforce our network and provide gas to our customers. "But because the works were being undertaken on third party land we had to convince the stakeholders to agree with our way of thinking and allow us on to their land to carry out the work." The first high profile stakeholder was the Royal Hospital Chelsea, which is home to the Chelsea pensioners. It's also the site where the Royal Chelsea Flower Show takes place. "The Royal Hospital is a national institu - tion and is home to one of the most famous flower shows in the world," remarked Hejd- ner. "There was a bit of trepidation around approaching the Chelsea Pensioners to tell them we wanted to dig up their grounds and construct a big project in their garden. Initially this was met with some resistance, Talking tunnelling Cadent has almost completed work on its biggest civil engineering project - a 330m long tunnel under the River Thames. Network editor Alec Peachey spoke to project manager Andrew Hejdner. but over the course of several meetings and building relationships with stakeholders, they understood why we needed to do it. We'd taken a measured approach in our feasibility study and identified that the hos- pital was a really good site for us to go from the north of the river, across to the south and into Battersea Park." Cadent also had to convince Wandsworth Council of the need for the works - they look a„er Battersea Park. Major events at the Royal Hospital Chel - sea, most notably the Chelsea Flower Show and arts fair Masterpiece, also had to be factored into the project timetable. More than 100 people have been involved with the project through planning, design and construction. Hejdner admits that there was extra pressure brought about by working at such iconic locations. The project team also had to engage with the Crown Estate who mange the River Thames on behalf of the Queen. "We had to get permission from the Crown for tunnelling and also had to speak to local authorities," notes Hejdner. "There was a big interface with Thames Water because we were working in proximity to some existing Victorian brick sewers. The biggest interface we had was with Thames Tideway. They had safeguarded the zone where they would be tunnelling along the centre of the River Thames. So we had over 12 months of engagement with Tideway to develop our design so that it wouldn't affect their proposed future works." The big breakthrough In November 2017, a Tunnel Boring Machine (TBM) named Amanda completed its tunnel drive under the River Thames. Tunnelling took 24 days to complete with TBM Amanda being controlled remotely by an above ground operator. Around 4,500m 3 of material was exca- vated from the tunnel and sha„s – approxi- mately the same size as 30 double decker buses. TBM Amanda was named a„er Royal Hospital Chelsea Infirmary Business Man - ager Amanda Lord. TIMETABLE OF WORKS November 2016 to April 2017 – north shaft installed at Royal Hospital Chelsea. April 2017 to August 2017 – south shaft installed at Battersea Park. September 2017 to December 2017 – tunnelling from north to south. January 2018 to April 2018 – gas pipe line installed. Demobilise. September 2018 to December 2018 – finish off works. Hejdner said: "We ran a 24/7 operation, which was on a shi„ rotation. Progress towards the end was slower because of the pressures for the hydraulic rams – they're pushing the whole 330m length at the end. This means that there's a lot of weight that has to be pushed so the progress gets slower the further you go along." So what has Hejdner learnt from carry - ing out this project? "The one main thing I've taken away from this project is that an effective stake- holder mapping and managing exercise is crucial to the success of a big project like this. We encountered a number of different stakeholders in various guises. You've got to make sure you have a consistent message. "I'm pleased to say that it all worked out well and the tunnel was completed on time and in budget. The pipeline has been installed and tested and we're about to commission it over the course of the next few weeks. Hejdner is full of praise for the staff that have worked on the project. "This project has been a success purely down to the fact that we have some excel - lent people involved. All the way through from the design stage through to the construction stage. The designers, the en- gineers, construction team, the sub-contrac- tors, everyone pulled together because they understood the nature of these works and the time constraints we were up against." Want to be featured in this section? Contact alecpeachey@fav-house.com