Posted: 4 August 2016
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Going underground

National Grid is busy laying the groundwork for the longest pipeline river crossing in a tunnel anywhere in the world. Senior Project Manager Phil Croft shares the latest on the pioneering Feeder 9 replacement project.

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Going underground

Going underground

The project sets out to replace an ageing section of gas pipeline that’s buried deep in the River Humber with a brand new one, by tunnelling under the estuary and inserting 5km of pipe into the tunnel.

“Tunnelling itself won’t begin until August next year, but we’re doing a huge amount of groundwork before the boring machine begins to turn.”

Phil Croft, Senior Project Manager.

Insight:

We have awarded the £100m contract to Pipe9JV, who will be responsible for completing the tunnel’s detailed design and then construction.

Source: National Grid.

A crucial few months on our Feeder 9 Humber Crossing Replacement Project have been awash with early challenges and successes as we take a bold and innovative step forward to counteract risk on our network.

If you don’t already know the background, the project sets out to replace an ageing section of gas pipeline that’s buried deep in the River Humber with a brand new one. The exciting innovation is that we’re doing this by tunnelling under the estuary, almost at the same point as the existing pipeline, and inserting 5km of pipe into the tunnel. It’ll be the longest pipeline river crossing in a tunnel anywhere in the world and, from an environmental and cost perspective, is the best solution.

Tunnelling itself won’t begin until August next year, but there’s a huge amount of groundwork to be done before the boring machine can start to run.

Project progress

In the past few months we’ve been carrying out all sorts of advanced works to prepare the site for excavation. While it’s still relatively early days for us, we’ve already faced some significant challenges which, through careful and disciplined project management, we’ve been able to overcome.

The most significant of these was negotiating a lease with the owners of the Humber to put our tunnel underneath it. The land is owned by the Queen – or the Crown – so we had to deal with the body that looks after the land on her behalf, the Association of British Ports. They’re responsible for everything from the surface of the water right through to the core of the earth. If you cross that vertical line, you have to get a lease to put your equipment there. So we needed to have that in place before we could continue. The conversation was challenging, but we managed to answer all their questions and progress the project from there.

We’re also delighted with our selection of the contractor to complete the tunnel’s detailed design and then construct it. The contract is worth around £100m, and we always wanted to award to a single entity for the complete works. In the end we awarded the contract to Pipe9JV. It’s made up of three businesses, construction company Skanska, pipeline specialists A.Hak and tunneling specialists PORR. It’s a major success to have so much experience onboard to meet the unique challenges of the project. We signed the contract in April, so we’re off and running and can really pick up the pace now.

National interest

A key piece of the project jigsaw was obtaining planning permission and consent. This requires something called a Development Consent Order (DCO), which has been a 15 month process and will conclude at the end of August. We’re still awaiting the final decision, but we believe we’ve done everything required and have confidence that it’s progressing well.

Because we knew the DCO process would be lengthy, we identified early on that running local planning permission alongside it would allow us to progress a number of preliminary activities this summer – and reduce the duration of the project by a year.

Much of this critical enabling work – such as site surveys for ecology, agriculture and archeology – can only be done in certain months of the year. So if we’d waited for the DCO decision, we’d have put ourselves back considerably. So we’ve basically assessed the risk of progressing immediately and built a programme that reinforces our network as soon as possible.

By obtaining this local planning permission, we’ve been able to carry out the following work:

– Protecting water voles
Water voles are a protected species, so we had to make sure the area that we’re planning to work in was clear of them. If we found any, we’d need to obtain a licence to relocate them. This relocation could only happen before April, so we had to survey the area, strim river banks and look for burrows all before that date. This is now progressing and we can move things forward confident that the local water vole population hasn’t been affected.

– Protecting nesting birds
Certain species of bird like to nest in hedges, rather than trees. As our project involves removing some hedges, we had to make sure we weren’t disturbing any nests. This involved carrying out surveys of birds’ movements to make sure that where we plan to build wouldn’t affect the birds’ habitat.

– Protecting archeology
We also had to make sure there was no valuable archeology buried in the land that we intend to excavate. Proving this involved checking historical records and digging trial trenches, which were then inspected by archeologists to check we wouldn’t disturb valuable relics. We have made some minor discoveries (pictured below) that we intend to share with the authorities and local communities.archaeology_720x480

The next crucial milestone is the selection of the tunnel boring machine (TBM) itself, which will take on the tough job of tunneling for a full year! This decision will be made by the contractor, but they’ll have to prove their selection meets our requirements on safety, reliability and cost. It’s a big decision and one they simply can’t get wrong. A choice needs to be made this month in order to give the manufacturer sufficient time to build the machine for our scheduled start date. It’s an enormously expensive, but critical moment for the project.

The focus now is to get all our enabling works finished and the site established by the end of summer, so we can work through the winter and be ready to start excavation for the TBM’s launch shaft in January.

Everything so far is progressing to plan and we’re thrilled to be working on an innovation that will help safeguard security of supply and deliver a project that will be the envy of the world.

And finally…

Sustainability is at the heart of the Feeder 9 replacement and we’re committed to cutting waste and carbon throughout the journey of the project. We’re keen to share this message with the local community and have been developing a sustainability game. We’ll take the game into schools to enhance pupils’ learning about National Grid, our commitment to sustainability and the incredible innovation on Feeder 9.

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