Advantage Geomatics were recently called upon to assist with a large infrastructure job on the Suffolk coast.
Located about 27km off the Suffolk coast the Galloper Offshore Wind Farm project has been under construction for nearly three years with 56 wind turbines being installed as part of the UK’s drive to produce 20% of its energy through renewable methods by 2020.
Figure 1 Topcon Hiper SR GNSS
Working as part of the team led by VBMS, Advantage Geomatics were commissioned to assist with the cable laying operation where the cable delivering the generated power makes landfall and crosses the beach.
The operation took place over a weekend in June to coincide with the spring tides, giving the lowest tides and longest window to work on the beach. The work entailed firstly locating the cable from where it had previously been buried at a shallow depth, exposing it and then laying it to the required depth, measuring its position and re-burying it.
Working with the tides, time was at a premium so we had to work quickly and efficiently to ensure the job was completed within the two nights otherwise the next opportunity would have been the next spring tide, a month later.
Figure 2 Not your usual QHSE signage!
Working with the tides, time was at a premium so we had to work quickly and efficiently to ensure the job was completed within the two nights otherwise the next opportunity would have been the next spring tide, a month later.
We managed to push the amount of cable exposed and re-buried to a greater depth to the maximum thanks to the efficiency and speed of the excavator operators. Digging large amounts of sand and gravel feels a bit like 2 steps forward and 1 back but the cable was exposed and measured using the Topcon Hiper SR GNSS equipment, it’s not often that you see a negative height on your equipment but this was observed for almost every point.
Figure 3 VBMS Landfall crew hard at work
Once the tide reached the lowest point it was pretty much operation over as every wave from then on will encroach back into the exposed hole and you cannot fight a rising tide, many have tried but asKing Canute demonstrated there are some forces that won’t be stopped. At that point we had achieved all we could, the excavator operators built up a bund to protect the Coffer Dam and we were able to download and process the data, using AiC n4ce software, in the beach site office and show the client a section drawing showing the comparison between the previous cable depth and the new, lower depth.
See the photographs below to illustrate the operation.
Figure 4 Bund protecting the Coffer Dam
Figure 5 Site of the Cable Landfall site, in the shadow of Sizewell Power Station
Figure 6 Excavators chasing the outgoing tide
