Purpose
Scottish Power Renewables’ East Anglia ONE (EA ONE) offshore windfarm is designed to provide 714 megawatts of generating capacity, powering over half a million homes. It was the first of four major offshore windfarms to be constructed 45km from the Anglian coast.
Landside works involved connecting six underground cables, from Bawdsey on the Suffolk coast to a new transformer at Burstall inland substation, which connects the offshore wind farm to the national grid.
Safely and sustainably crossing the many obstacles along the 37km cable route was key to the success of the £2.5 billion project. Iberdrola partnered with our specialist business, VolkerTrenchless Solutions to overcome these challenging obstacles using horizontal directional drilling (HDD) and auger boring techniques.
What we did
The cable route crossed the River Deben, two railway lines, the A12, A14, and other roads, as well as protected ancient woodlands. Our team prioritised environmental management and sustainability, whilst working in extremely challenging and fluctuating conditions.
Our in-house construction experts helped to optimise drilling methods and select the best plant and equipment based on decades of HDD experience. Key members of our team were involved from the tender, through feasibility studies, and on into construction. During the six-month feasibility period, they developed a thorough understanding of the project requirements and challenges. They surveyed all 21 locations and developed the optimum design for each site, taking into consideration the specific constraints, ground conditions, environment and topography.
Delays in pre-construction, when the scope changed 60 times to account for archaeological and environmental constraints, ramped up the pressure on our teams to meet our client’s programme. Our seven days a week, six-month production period was the most intensive ever known in the HDD sector in Europe. We installed 50,000m of duct within 148 crossings. We used drilling rigs ranging from 17t to 450t to undertake HDD drills, from less than 100m to over 1km.
We achieved industry-leading productivity, by selecting the correct drilling tools and ancillary equipment for the varying ground conditions - glacial till, sands and gravel, stiff clay and silty clay. We used live monitoring to feed ground condition and drilling progress data back into our system, compared output with estimates, and continually improve the tooling design for the next drill.
We carefully planned site logistics, so the right rig could get to the right site at the right time. By programming the drilling locations so that different sized rigs could work simultaneously, and by optimising time between rig maintenance periods, we drastically cut downtime. Similarly, we reduced lost time by siting our compounds in locations that minimised travel to site.
Project successes
ScottishPower Renewables completed the installation and commissioning of the £2.5 billion East Anglia ONE offshore windfarm project on time thanks to the work of our team and others. East Anglia ONE will now play a major part in contributing to the UK’s target of meeting Net Zero by 2050.
We helped keep the overall project on track by using Europe’s biggest fleet of rigs and the above efficiencies to save 40 weeks on our construction programme. We maximised productivity by using the full capacity of our trenchless fleet with up to eight HDD and Auger Bore rigs working at same time.
We worked two million hours with no reportable accidents, despite the challenges of a large team of over 100 people working across a 37km linear site.
We developed a system of 6ft x 2ft metal plates which slotted together to form an instant hardstanding area, more resilient than traditional trackway, eliminating delays due to poor site access. We own 30,000 of these plates and a dedicated truck could lay 400m per day.
By using bespoke heated containers, we welded the HDPE pipes more quickly than in the open air. This meant we could push our drilling rig deployment to the maximum. We delivered 4000 welds on the HDPE, with zero defects.
The UK Society for Trenchless Technology (UKSTT) recognised our work as award-winning. The UKSTT is the only UK Society dedicated to promoting the use of trenchless technologies for the installation and repair of underground utilities. In September 2019 they presented our project team with the award for ‘Best New Installation Project—Energy and Communications.’