On the Triton-Knoll project, Murphy provided full EPCI of the onshore cable system from the Landfall at Anderby Creek to the new Triton Knoll substation at Bicker Fen. This comprised installing two 220kV AC cable circuits across 58km of predominantly rich arable farmland. Murphy employed over 200 people on the project plus key Supply Chain Partners providing cable, drainage and HDD works. Murphy also designed and constructed the Transition Joint Bay (TJB) compound as part of the landfall HDD.

Murphy was responsible for the design of the full works, including the cable system design and all civils and temporary works along the route. This crossed 483 obstacles (425 ditches, 52 roads, 3 rail, 2 rivers and 1 NG pipeline) using horizontal directional drilling, making it one of the largest HDD projects ever completed in the UK, with 146 HDD crossings of various obstructions along the route. It was also our responsibility to manage the third-party interfaces with both the substation and offshore works contractors, along with ensuring the Onshore Export Cable system complied with TKOWLs overall system design and technical requirements. The cable was procured by Murphy and supplied by Nexans, who also provided Design Verification, Cable Manufacture / FATs / Delivery and Cable Jointing services.

The project included:

  • 146 HDD crossings undertaken by three specialist HDD Supply Chain Partners, with up to 9 HDD’s being undertaken concurrently.
  • 3 rail-crossings managed by Murphy’s specialist teams who liaised with NR on a daily basis as part of our Transport division.
  • 425 ditch crossings, including 183 flumed crossings and 3 bailey bridge crossings

On the project, our design reduced the number of cable sections and optimised the system design via a direct bonded system, negating the need for 28 link boxes. This provided a substantial saving and will reduce access/maintenance costs over the 25-year lifespan of the project.

Our design specified two circuits with 4 trench configurations We undertook a phased installation, excavating trenches, duct install and backfill in adjacent sections whilst maintaining 1km working space between the teams working on each circuit. Informed by our GI investigations and temporary works designs, we designed and manufactured bespoke V-buckets to cut a uniform angle of batter into the trench walls. We also deployed our in-house prototyped and developed duct laying trailer system and CBS/Sand Dispenser to negate the requirement for operatives to enter the cable trench, thereby minimising resource risk exposure. Our cable sections ranged in length from 800m to 1600m. We designed 100 joint bays (50 joint bay locations, 1 for each circuit). Our optimised cable system design required us to install link boxes at 11 of the 50 joint bay locations. The link boxes utilised a bespoke design that eased installation and reduced overall cost, with the chambers cast in the main yard to reduce the need for cast in situ concrete works at the link box locations