BLOCK 3 BLOCK 2 U e c n France 400000 570000 KP 0 KP 10 KP 20 KP 30 a r F 565000 BLOCK 1 450000 Belgique 0 5 ONGOING 10 15 20 km N 565000 t i n g n i K Nearshore BE Fra m o d ed KP 50 KP 60 KP 70 KP 80 Offshore BE ue lgiq Be e nc United Kingdom 500000 Offshore FR KP 90 KP 110 KP 100 Offshore UK KP 120 570000 Nearshore UK 450000 KP 40 400000 500000 Nemo Link s puxo campaign UXO is unexploded ordnance left on the seabed as a result of historic military and other activities e.g. sea mines or bombs (dropped by planes) from World War I and II. D uring the Nemo subsea cable installation, UXOs could be disturbed or activated. T here is a risk that this could result in an explosion and threaten the safety of the team, cable and other key assets, including robots and vessels. N emo Link undertook a campaign to identify UXOs along the subsea cable route and to neutralize them in order to ensure the installation works could be carried out safely. Nemo Link banners.indd 1
Inspection and disposal I n 2016, we carried out a detailed seabed survey and route engineering analysis. Out of 12,000 detected anomalies, 1,200 were judged to be potential UXOs (puxos) and after further analysis, we created a target list of 985 puxos to be physically inspected. T he physical inspection of the 985 targets has been carried out using diving robots in deep water areas or divers when robots cannot be submerged because of shallow water. A Target Investigate Report is then produced for each target and a Report of Find submitted to the relevant country s Authority. I f an object is confirmed as a UXO in Belgian or French waters, it is disposed of by the relevant Marine Authority depending on its location. I n the UK, the Royal Navy disposes of UXOs if it is considered to pose an imminent threat to the waters. In all other cases, the Nemo Link team works with special contractors to neutralise the UXOs. Nemo Link banners.indd 2
Detonation of the German 1000 kg LMB by Nemo Link German 1000kg LMB/GC parachute mine German GZ/UMA moored contact mine WW II What we found: UXOs and heritage 1,200 puxos were identified along the 130km Nemo Link subsea cable route. Of these, 20 have been confirmed as UXOs so far. Most have now been neutralised. Nemo Link banners.indd 3
What we found: UXOs and heritage The Nemo Link team has also made a number of interesting archaeological finds. Each has been investigated and reported to the relevant Authorities. UK nearshore: A cannon and cannon ball, anchor and aircraft wing. French waters: A shipwreck (14th Century) Nemo Link banners.indd 4
Phasing of the offshore works (UK side) Phase 1 Preparatory works June August Pre-sweeping Before installing the cable, we will pre-sweep or dredge the sand waves along the cable route so we can deploy and operate trenching machines. In the southern North Sea, which is shallow and sandy, a cable could be exposed to the movement of sand waves over time. To minimise the risk of the cable being exposed and ensure the trenching vehicles can work effectively, a corridor will be dredged to a similar level of the toughs of surrounding sand waves. The cable will then be buried below this new mean seabed level using jetting or mechanical trenching equipment. Pre-Lay Grapnel Run (PLGR) route clearance operations A clearance operation called a PLGR will also be carried out to remove debris from the seabed. Phase 2 Load-out August September The HVDC cable has been transported to the Port of Blyth, Northumberland, in the UK, from the JPS factory in Japan on a Submarine Cable Transportation Vessel (SCTV), the Global Arc. The cable will be trans-pooled from the Global Arc to the Cable Lay Vessel (CLV), the Maersk Connector. Cable testing will be carried out before, during and after the loadout is completed by cable contractor. Phase 3 Installation and cable laying September October The Maersk Connector will be used to transport the cable from the Port of Blyth and to lay the cable in deeper waters (circa >10m). A shallow water Cable Laying Barge (CLB), the BoDo Installer, will be used to transfer a portion of the cable at sea and lay and trench the cable from KP 120 to the UK shore. KP 120 to KP 128 Cable laying and burial: Installation and burial of the cable is a combined process using the simultaneous lay and burial technique. The cable is trans-spooled from the Maersk Connector to the BoDo Installer in the near shore area, off Ramsgate. The CLB will then complete the near shore lay and trench. Cable landing and beach pull-in: It is anticipated the CLB can install the cables up to approximately KP 128, where it will ground. The cables will then be spooled off and pulled out in a bight during low tide and laid on cable rollers positioned over the beach. From KP 120 to KP 71 Cable laying: Once the cable has been successfully secured to the beach, the CLV will begin to move and lay the cable. Typically, the vessel will lay bundled cable at 350 meters per hour. Cable burial: All offshore areas will be trenched from the Trenching Support Vessel (TSV), the Havila Phoenix the world s largest trencher. The TSV will follow the CLV and bury the cable to minimise the duration of exposed cable and the use of guard vessels. This process will be completed within two weeks. Nemo Link banners.indd 5
2018 project timeline offshore cable works (UK side) Jun Jul Aug Sep Oct Pre-sweep UK and France Gerardus Mercator Dredger Mobilisation and Commissioning in the Port of Blyth Maersk Connector Load cable at the Port of Blyth Maersk Connector, AHT Forth Jouster and Global Arc PLGR activities BoDo Installer and AHT Barney / Valour Transit from Blyth for cable lay trials and conduct trials Maersk Connector and AHT Forth Jouster BoDo Installer standby in Ramsgate for trans-pooling BoDo Installer Trans-pooling 9km offshore Maersk Connector to BoDo Installer Cable lay and burial from 9km offshore to shore BoDo Installer and AHT Barney / Valour Cable lay KP120 KP71 (49km) Maersk Connector Ramsgate shore preparation and cable pulling works Trenching KP120 KP71 Havila Phoenix Nemo Link banners.indd 6