Licensed to drill: Feeder 9 update
With planning approved by the Secretary of State and the site establishment works proceeding at pace, National Grid’s ground-breaking Feeder 9 pipeline replacement project is ready to kick off its major works. Project Manager Steve Ellison drills out the latest developments
Licensed to drill: Feeder 9 update
"With innovation at its heart, the project is capturing the imagination of the tunnelling and pipeline industries, as well as our customers and stakeholders"
Steve Ellison, Project Manager, National Grid.
48 acres of topsoil was cleared from the site in just three weeks.
Source: National Grid.
As an engineer, there’s nothing more rewarding or exhilarating than working on a project that’s genuinely cutting-edge. I’m lucky enough to be leading one such project, our Feeder 9 pipeline replacement, which will see us bore a 5km tunnel beneath the River Humber and create Europe’s longest pipeline tunnel river crossing.
The project is all about delivering the safest, most sustainable and cost-effective solution for replacing a section of gas pipeline that’s become exposed over time in the Humber with a brand new one.
The really innovative bit is that we’re doing this by tunnelling under the estuary for a full year and inserting 5km of pipe into the tunnel. With innovation at its heart, the project is capturing the imagination of the tunnelling and pipeline industries, as well as our customers and stakeholders.
In our previous update here on Connecting, we explained the early work we’d been carrying out, including preparing the site for excavation, the long process for obtaining national planning (through a Development Consent Order – or DCO), and our crucial search for first-rate contractors.
Since then, the project has moved on considerably. Planning has been agreed by the Secretary of State, we’ve carried out most of the work necessary to get the site ready for tunnelling, we’ve chosen a trio of outstanding contractors to deliver the work, and we’ve selected a £7m tunnel boring machine (TBM), which is currently being built.
Establishing the site
Our recent focus has been on preparing the site for the major tunnelling works that lie ahead. So we’ve been clearing access routes on to site, removing topsoil and laying hard-standing, putting in welfare facilities for workers, fencing and draining the site. By carrying out these enabling works when we did, we gave ourselves a head start, so that when we received the DCO, we’d be ready to go.
One of our biggest successes so far was clearing 48 acres of topsoil from the site in just three weeks. It’s vital that we strip back the topsoil, because it’s those few inches that are the farmer’s main resource. So we need to take it off and store it safely to protect the landowner’s livelihood.
If you imagine how you might lift a carpet at home and roll it into one corner, that’s effectively what we did with the topsoil, but on a much larger scale. We started at the top of the field, with a large number of excavators and bulldozers in place, and then worked together to push all the topsoil up to one edge. It will remain there until the project’s finished and we’ll then spread it back out across the field.
Achieving this in three weeks was a massive challenge. We had to mobilise large numbers of machines onto the site quickly and effectively, ensuring those contractors – who may never have worked with us before – understood the high standards National Grid adheres to, and that the whole process was managed safely and effectively.
If you’ve ever seen the TV show Time Team, you’ll understand some of the work we had to do in terms of archeology at the site. As we lifted the topsoil, we uncovered all kinds of relics, from Roman and Iron Age pottery, to Iron Age roundhouses. As part of our requirements for the project we had to ensure that all historical finds were recorded. So just like the aforementioned show, experts were called in to make full records of the finds before we could progress.
As well as being mindful of archeology, we had an obligation – as well as a desire – not to harm any wildlife. We’re working in an incredibly biodiverse area with all sorts of protected species, such as water voles, badgers and rare birds.
Our protection work included relocating water voles from ditches that would be affected by building access points, reducing the number of badger sets on site, and creating work exclusion zones so we don’t disturb a rare bird called the Marsh Harrier or its young. All this work, which was licensed by environmental bodies such as Natural England, required careful preparation and management as we’ve strived to limit our impact on the local environment.
Managing traffic was another key area for focus. The fact is that we’re working in quite a rural area. We’ll need to increase the number of vehicles coming to site, so we need to manage this in a way that means local people don’t get delayed. Our solution, based on feedback from the nearby community, has been to build a dedicated temporary bypass for work traffic, which is now in progress.
Planning comes together
Our DCO was recently granted – and this provides us with the green light to proceed. The DCO is a process you need to go through if you’re proposing a nationally significant project. While it’s been a lengthy process, we now have a really thorough, prescriptive approval document that sets the benchmark for what we have to deliver on site throughout the project.
Another benefit is that all stakeholders in the area have been consulted and certain conditions, based on their input, are set into the DCO. What that means is that we can go ahead knowing that the planning application itself has the buy-in of local people and stakeholders. So we’re good to go.
The main works will begin at the start of December and our first task will be to build the TBM’s launch shaft, a 15m deep pit from which it will start to tunnel. Building the pit will take until June, after which the TBM will start its 12-month tunnelling trek across the Humber.
A common question we get asked is how we know what the TBM will encounter when it starts turning. The answer is that we don’t exactly, but we do have lots of intelligence based on significant ground investigations, including drilling 30 bore holes along the tunnel alignment. From this we know that the TBM will tunnel mostly through chalk – and that actually formed the basis for the type of TBM we ordered.
Once built, our Feeder 9 replacement will be an incredible feat of engineering that reinforces the safety of our network long into the future. While there’s a huge amount of work to do and challenges to overcome, it’s an incredible journey to be a part of.
Meet the contractors
Selecting the right partners for the project was paramount for National Grid and the business opted for a joint venture (JV) – made up of three businesses – to carry out the main work. The JV is called Pipe9JV, and comprises Skanska, a renowned engineering management company with vast experience building big projects; A.Hak, a European pipeline organisation with lots of experience; and PORR, a renowned Austrian tunnelling organisation with significant experience in operating the type of TBM that will be used. “We’ve got a really balanced team here, with world-class engineering, tunnelling and pipeline expertise,” said Steve. “The combination of skills really is the perfect fit.”
In a previous Feeder 9 update Phil Croft explains the earlier work that was carried out, including preparing the site for excavation, the long process for obtaining national planning (through a Development Consent Order – or DCO), and the crucial search for first-rate contractors.