Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
Review of Cabling Techniques and Environmental Effects Applicable
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<strong>Review</strong> <strong>of</strong> <strong>Cabling</strong> <strong>Techniques</strong> <strong>and</strong> <strong>Environmental</strong> <strong>Effects</strong> <strong>Applicable</strong> to the Offshore Wind<br />
Farm Industry – Technical Report<br />
3.7.8 CURRENT BURIAL TARGETS FOR THE OFFSHORE WIND FARM<br />
INDUSTRY<br />
The <strong>of</strong>fshore wind farm industry has generally recognised that the main risks<br />
posed to the subsea cables derives largely from inshore fishing activity <strong>and</strong><br />
dragging anchors from coastal vessel traffic. Typical target depths <strong>of</strong> burial<br />
between 1m <strong>and</strong> 2m have been specified for the majority <strong>of</strong> the Round 1 sites<br />
which have been developed to date. However, as the Round 2 developments<br />
move into deeper water, cable risk assessment may identify the need for<br />
increased burial depths as the possibility <strong>of</strong> anchor damage from larger seagoing<br />
vessels has to be considered.<br />
The use <strong>of</strong> burial assessment surveys may increasingly be used to establish<br />
target burial depths for cables. This procedure is explained in more detail in<br />
Section 3.10 <strong>of</strong> this report.<br />
3.7.9 REMEDIAL MEASURES<br />
Cable burial is the primary method for protecting subsea cables. Providing<br />
the correct burial machine is selected for the designated burial task, the target<br />
depth <strong>of</strong> burial is likely to be achieved. However, occasionally reduced burial or<br />
zero burial occurs. This will usually result as a consequence <strong>of</strong> an unforeseen<br />
event such as extreme weather; the departure from the scheduled installation<br />
procedure; extreme ground conditions which were not anticipated from the<br />
original survey; or equipment failure. Remedial measures will be required if the<br />
perceived risk for the installed cable is considered too high. In many cases it will<br />
not be possible to re-engage the cable with the original cable burial machine<br />
(i.e. subsea cable plough or tracked cable burial machine with enclosed cable<br />
path). In such cases the only remedial burial option available will be post lay<br />
burial by other means. Most post lay burial machines only utilise jetting systems<br />
which straddle the surface laid section <strong>of</strong> cable <strong>and</strong> these machines have<br />
limited capability when working in hard seabeds. Alternative cable protection<br />
methodologies which are reviewed in Section 3.8.6 can also be employed as a<br />
means <strong>of</strong> remedial protection for the installed subsea cable.<br />
3.8 Cable Protection Methods<br />
This section describes the methods which are currently used to protect subsea<br />
cables in the subsea telecommunications, power cable <strong>and</strong> oil <strong>and</strong> gas industries<br />
worldwide.<br />
Section 3.9 <strong>of</strong> this report focuses specifically on the cable protection methods<br />
which are relevant to the <strong>of</strong>fshore wind farm industry. Section 3.9 does not repeat<br />
the methodologies as chronologically listed in this Section 3.8, but summarises<br />
the methodologies used on wind farms installed to date <strong>and</strong> also lists the cable<br />
protection methodologies considered relevant for current <strong>and</strong> future <strong>of</strong>fshore<br />
wind farm developments.<br />
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