Beatrice Wind Farm CASE STUDY-BEATRICE WIND FARM Located 13km off the Cathiness coast, Beatrice is the UK’s largest wind farm. The farm is made up of 84 turbines each equipped with three 75m blades. At capacity it will be able to provide the power for 450,000 homes. The electricity generated is sent via subsea cables to landfall west of Portgordon, a distance of 60km. From Portgordon the electricity is sent a further 20km via buried cables to the Beatrice substation at Blackhillock. After delays caused by contracting challenges, Nicol was awarded a contract by Murphy Group to drill two critical boreholes under the A95 and A96. Scottish and Southern Energy is the majority shareholder in Beatrice Offshore Windfarm Ltd (BOWL). BOWL appointed French cabling and connectivity experts, Nexans, to manage cable installation and they, in turn, appointed Murphy Group for onshore civils work. The project involved two circuits with each circuit consisting of four elements: three 225mm power cables and a 125mm fibre optic cable. The borehole was reamed to a bore of 610mm (24”). The combined heat generated by the cables and the subsoil meant that a separation of at least 12m had to be maintained. An open cut element of the project is shown below: Overview of the Beatrice wind farm cabling and directional drilling requirements Both trenching and directional drilling techniques were used on the project Time was of the essence on the project and there were substantial potential fines for the supply chain for every day after the agreed completion date. The project had already been delayed due to snow, earlier contracting issues, and delays in receiving permissions from Network Rail to drill under the rail line close to the A95. Boring under the rail line was exceptionally challenging due to the specifications demanded by the Network Rail engineering team, and the substrate on which the railway was built. Network Rail’s specification stated that the borehole must be a minimum of 9m below the surface, but that the depth could not exceed 9.7m. This provided a tolerance on the drill path of 100mm. Site investigations had identified that the railway was built on what was, effectively, an old 3,500t waste tip. The volatility of this substrate meant that prisms were used to monitor potential changes in ground levels. Bore plans were agreed with Network Rail and a Network Rail engineer was on site throughout this element of the project which was completed successfully. The drill paths for the two elements of the project were as follows: A95: road – field – railway – burn – exit A96: road – field – burn – road – exit Two Ditch Witch all-terrain rigs were used on the project – JT60 and JT100 – although only one needed to be equipped with tricone drilling heads to drill through rock. KEY BENEFITS Innovation There were no specific innovations on this project. The key feature of the project was Nicol’s ability to use incredibly powerful all-terrain rigs within exceptionally tight tolerances. Environment The two drill paths took the cable under burns in an area where water quality is high profile due to the proliferation of distilleries. Community impact and customer care The use of directional drilling, and in particular the success of the drill path under the railway, ensured that disruption to transport routes was minimised. Project management Close co-operation with all stakeholders and, in particular, with Network Rail was key to the successful completion of this project. Legislative compliance Project Beatrice complied with all relevant health and safety legislation, including CDM. We worked closely with the prime contractor, Murphy Group, to ensure that there was no diminution of best safety practices on site whilst under sever time pressures. The Nicol difference Nicol successfully delivered this technically challenging project within tight time constraints. The close working relationship built up with the Network Rail engineering team was critical to allaying their understandable concerns regarding the use of directional drilling within such tight tolerances.