Review of Cabling Techniques and Environmental Effects Applicable

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Review of Cabling Techniques and Environmental Effects Applicable to the Offshore Wind Farm Industry – Technical Report Figure 3.25: Typical Detail for the Cable Crossing Arrangement using Concrete Mattresses to Provide Separation and Cover Rock dumping Rock dumping is an established methodology for protecting subsea cables both along their installed lengths and also at crossings with existing subsea cables or pipelines. Many of the major offshore rock dumping contractors such as Van Oord, claim the technique is very resistant to both trawling and anchoring activities. However, rock dumping is not generally favoured by fishermen who claim it sets up a potential snagging point for their fishing gear. Furthermore, certain groups see the introduction of substrates which are foreign to the locality as falling into the category of undesirable. However, there is a counter review from other groups who view the introduction of a new rock reef as a potential new habitat for fish and other underwater species to colonise. In shallower waters rock dumping is usually achieved either by the use of side tipping vessels which deposit their cargo in a somewhat crude method that often results in the need for larger volumes of rock to achieve the primary protection method or by using a grab device which is illustrated in Figure 3.26. 60
Figure 3.26: Placement of Rock for Scour Protection Grout bags or sand bags Cable types and installation techniques Grout or sand bags can be regarded as a smaller scale version of the mattressing process. They are usually installed by divers to stabilise or fix in place a cable or a pipeline over short distances. Grout bags can either be deployed as pre-filled bags or for larger applications empty fabric bags are taken to the seabed and a diver coordinates the filling of the grout bag using a grout mix and pumping spread from the host vessel above. Figure 3.27 shows a Grout Bag (in an onshore trial) which has been placed over a pipe section and filled with grout. Figure 3.27: Grout Bag over a Pipe Section and Filled with Grout 61
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REVIEW OF CABLING TECHNIQUES AND EN
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Review of Cabling Techniques and En
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Abbreviations AIS Automatic Identif
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Page 20 and 21: 3 Cable types and 18 installation t
Page 82 and 83: 4 Physical change 4.1 Introduction
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6 Good practice measures This secti
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7 Gaps in understanding Research fo
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References Introduction Sinden, G.
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Appendix A: Standards and codes of
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Printed in UK on recycled paper. De
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