Purpose
Hornsea 2 is the world’s largest offshore wind farm and the second offshore wind farm within this zone of the North Sea, with a total capacity of 1,386MW capable of supplying clean electricity to 1.3 million UK homes. The wind farm is located 89km off the Yorkshire coast, with an export cable coming ashore near North Cotes in Lincolnshire.
VolkerInfra’s role in the project was to complete all the civils works associated with the 38km onshore cable route. This included installing underground circuits within a 40m-wide construction corridor, consisting of three 220kV export cables and fibre optics. The cables will carry electricity from the newly constructed Hornsea 2 substation to National Grid’s North Killingholme substation.
What we did
A 38km geotextile and geogrid haul road was needed to access the works. Our engineers and temporary works specialists revisited the original plans and managed to reduce the length to 18km, eliminating 52,800 tonnes of 6F5 stone and more than 5,000 wagon movements. Working with our supplier, we devised a safer, more efficient way to lay the geotextile and geogrid. Our ‘sledge’ rolled the material out 40% more quickly whilst eliminating 95% of manual handling and people-plant interfaces – both key safety considerations.
We continuously improved our methodology, laying 360km of cable in total, at a rate of up to 1km/day. Following a review of the retaining walls for ditch crossings, we switched from the dusty operation of stockpiling limestone bulk bags to using prefilled, palletised 1000kg bulk bags. This increased the task’s productivity by 40%.
We also carried out 13.5km of horizontal directional drills across 62 locations, including crossing two railway lines, and designed and constructed 23 triple joint bays. We achieved 100% HV, LV and fibre test pass rates.
Throughout work on the project we met stringent environmental and ecological constraints. The cable route was carefully planned to avoid identified wildlife, such as badger setts, and incorporated newt crossings. We used acoustic barriers and super silent generators to minimise noise disturbance.
Project successes
We completed our cable route and the main contractor, Ørsted, is nearing completion of the huge overall scheme which will soon start generating clean electricity for UK homes and businesses.
We scored an impressive 44/50 on a Considerate Constructors Scheme audit. This evidences the positive social impact we had and the way we minimised disruption to the communities along the 38km construction corridor. We provided all operatives with our bespoke customer care training so that they could handle any ad-hoc enquiries from the public sensitively and direct people to the right point of contact if necessary.
We supported local jobs - two of our largest subcontractors, BNJ and Carnaby, were both located in the area. We donated waste timber generated by the site to Hull prison which makes timber products for donation to local charities. The prison also created planters and other items for a garden in our site compound.
We held several charity coffee and cake mornings, on one occasion raising more than £700 for MacMillan Cancer Support. All remaining cakes were donated to a nearby care home. At the end of the project we organised a community archaeology event as part of a legacy initiative.
On completion of the onshore cable installation element, Luke Bridgman, deputy director for Hornsea 2 at Ørsted, said: “Our teams have persevered relentlessly throughout this pandemic, for which we are deeply thankful. They have maintained a clear focus on collaborative behaviours, ensuring that the works were delivered with the highest standards of safety and within the original project programme.”
David Morgan, senior project lead at Ørsted said: “It has been a difficult year to deliver a project of this scale but VolkerInfra has been a great partner to tackle this challenge with."