Little Barford – St Neots HDD Project

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The requirement was the replacement of the Little Barford 132kV Air Insulated Switchgear (AIS) with new Gas Insulated Switchgear (GIS) at Little Barford and to establish 3rd Super Grid Transformer (SGT) connection with a single 132kV cable route between Little Barford and Eaton Socon with the objectives of...

  • Security of supply at Eaton Socon, Burwell and Sundon GSPs and major settlements including the City of Cambridge, Bedford and St Neots.
  • Reinforce the networks capacity.

The project involved a new cable route from Little Barford Grid to Eaton Socon Grid with a spare set of ducts in a separate parallel circuit for future usage. This required two HDD’s at each to location to install seven 180mm SDR11 electric cable ducts in each.

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A series of long and complex drills

As complex goes, the Little Barford to Eaton Socon project had it all; an important river, a golf course, flood plains, two national trunk roads, and a large industrial estate to cross in addition to pipe string out restrictions. It was even once labelled as a project that ‘could not be built’.

McCormack Drilling undertook the design of the HDD’s which included extensive surveys, calculations, extra ground investigation to complement the existing information through to obtaining approvals from Highways England to cross under the A1 and A428 roads.

Project Information
  • Utility: Electricity
  • Length: 850m x 2 shots, 230m x 2 shots, 750m x 2 shots, 220m x 2 shots
  • Depth: 13 - 25 metres
  • Pipe: 7 x 180mm SDR11 PE100 ECD pipes in 2 circuits
  • Geology: Oxford Clay Formation
  • Challenges
  • Testimonials
Engineering difficulty

With any long range HDD the issues not only involve the execution of the drilling process and all that it entails, but sometimes the viability of the project rests on one simple question, where do we string out the duct? Little Barford had HDD 1 (850m) and HDD 3 (750m), two locations with severely restricted pipe stringing capacity in that there was no continuous straight-line space to weld and layout the ducts for installation.

McCormack Drilling prides itself in finding solutions to these types of situation having encountered a similar scenario on a previous project immediately before Little Barford. The solution was to string the ducts out and hold them in position in a series of s-type bends with fixed point rollers cast in concrete along the radii of the bends to prevent the ducts ‘cheesewiring’. The system worked as per the design and the calculations

Community involvement

“Another impressive achievement for the ED1SON Alliance team as we successfully delivered a series of complex drills to provide a fully ducted cable route between Eaton Socon and Little Barford. The project wasn’t without it’s challenges but through collaborative working with Peter McCormack & Sons and our Alliance Delivery Partners UK Power Networks and Morrison Utility Services we was able to collectively deliver a cable route that had previously been considered not possible. It had a bit of everything with drills under a river, two major roads and a golf course and a vast number of key stakeholders to keep happy. The team should be very proud of what we achieved together”
Liam Bradley Senior Project Manager, Kier Utilities & Rail

“It’s been a challenging project with a series of complex drills under rivers, flood plains and a major arterial road route, but the entire team has risen to meet it. Once again we have delivered an essential HDD scheme on time and budget, allowing UK Power Networks to develop the rest of the impressive Little Barford HVP project."
Shane BarberSenior Operations Manager, Kier Utilities & Rail

“The completion of the HDD works between Little Barford and Eaton Socon was a significant milestone in what is a challenging, long term and complex project. It is the result of a significant amount of dedicated team work and fine engineering to deliver a cable route that “could not be built”. It is a credit to the team that such a significant milestone has been achieved and demonstrates Alliance working at its best."
Geraint Hancock Senior Project Manager – UK Power Networks