FEATURE SPONSOR
MARINE ORDNANCE
RACE BANK FROM MINE FIELD TO ALARP CERTIFICATION
From 40 years’ experience of seabed mapping and detecting various contacts on the seabed, the Swedish marine survey company MMT performed UXO inspections and excavations services of various contacts with option on disposal and removal at Race Bank offshore windfarm for DONG Energy Wind Power (2015). DONG Energy’s Race Bank project is located off England’s East Coast, an area situated in a region known for the presence of UXO.
PROJECT DETAIL
The project includes 91 wind turbine generators, two offshore substations and two export cables. Previous surveys have modelled a number of ferromagnetic and acoustic contacts at discrete locations as potential UXOs, which may impede windfarm component installation and therefore need to be verified and inspected visually for identification. Many of the ferromagnetic contacts were expected to be caused by objects buried by marine sediments.
METHOD
The ROV based inspection method used included electromagnetic pulse induction technology to verify non-ferrous and ferromagnetic contacts, excavation of buried contacts, visual inspection of contacts from side scan sonar, multibeam echo sounder and magnetometers.
After thorough data processing and interpretation by skilled specialists from both MMT and DONG Energy wind power consultants, the contacts that were suspected to pose a higher risk were investigated further. The following identification and classification resulted in 36 confirmed UXOs.
ROUTINE PREPARATORY WORK Eleftheria Melekou, DONG Energy Site Investigations Project Manager, said: “As a routine part of the preparatory work before construction of an offshore windfarm, seabed surveys are carried out to ensure the seabed is clear of obstacles including unexploded ordnance. The number of items discovered was higher than expected and the most we have seen on a DONG Energy project to date.”
UXO DISPOSAL
The next operation phase was disposal of the confirmed UXOs. The 36 confirmed UXOs were disposed by detonation onsite. The concern for wild life in the area was always high and precautions were taken to ensure the least possible environmental impact was caused, e.g. through close cooperation with the Marine Management Organisation and Natural England and using dedicated mammal observers to ensure the negative effects were kept to an absolute minimum.
MMT
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= Click to view video Hydrography & Marine Support
• Surface & Subsea Positioning • Construction Support
• Hydrographic Survey • ROV Inspection
T 44 (0)1208 77033 •
www.insight-marine.com www.windenergynetwork.co.uk 81
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