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 />
particular significance, given that each <strong>of</strong> these animals is afforded a high level<br />
<strong>of</strong> individual protection under a suite <strong>of</strong> national <strong>and</strong> international legislation<br />
<strong>and</strong> signatory agreements 3 (Defra, 2005). As such, potential adverse impacts<br />
upon a single individual <strong>of</strong> a species <strong>of</strong> marine mammal must be considered as<br />
being <strong>of</strong> significance <strong>and</strong>, therefore, there is a requirement to apply practicable<br />
<strong>and</strong> financially feasible mitigation measures in order to be compliant with the<br />
legislation (in particular, the Habitats Directive).<br />
5.6.1 POTENTIALLY SIGNIFICANT EFFECTS<br />
Cable laying operations have the potential to impact upon marine mammals<br />
through:<br />
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Collision with the vessel or support vessels;<br />
Noise <strong>and</strong> visual disturbance from the vessel <strong>and</strong> cable burial system;<br />
4 Contact with any fuels <strong>and</strong> chemicals that may be accidentally released<br />
during the operation; <strong>and</strong><br />
Interactions or entanglement with the cable or other lines between the vessel<br />
<strong>and</strong> the installation tool.<br />
Collision risk<br />
While there are no accurate records <strong>of</strong> the number <strong>of</strong> incidents <strong>of</strong> accidental<br />
collisions between marine mammals <strong>and</strong> shipping in UK waters (e.g. Hammond<br />
et al., 2003), it is considered that a direct relationship exists between shipping<br />
intensity, vessel speed <strong>and</strong> the number <strong>and</strong> severity <strong>of</strong> collisions, certainly in the<br />
case <strong>of</strong> whales (Laist et al., 2001). Certain assumptions can be made about the<br />
risk <strong>of</strong> collision with marine mammals (Sakhalin Energy Investment Company<br />
Limited, 2005; Laist et al., 2001):<br />
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All types <strong>and</strong> sizes <strong>of</strong> vessels can hit marine mammals;<br />
Vessels over 80m in length cause most severe or lethal injuries;<br />
Serious injuries to mammals rarely occur if struck by vessels travelling at<br />
speeds <strong>of</strong> less than 10 knots;<br />
Mammals struck by vessels are usually not seen prior to impact, or are seen<br />
too late to avoid impact; <strong>and</strong><br />
The risk <strong>of</strong> collision increases in poor visibility.<br />
Collisions between marine mammals <strong>and</strong> the cable burial vessel are considered<br />
to be unlikely. The cable burial vessel whilst working in the shallow water<br />
locations, is likely to only make very slow progress while laying <strong>and</strong> burying<br />
cable, with a burial rate <strong>of</strong> 1000m <strong>of</strong> installed cable per hour <strong>and</strong> therefore would<br />
4 Such accidental releases are likely to be similar in extent, duration <strong>and</strong> significance as for other parameters <strong>and</strong> is<br />
not discussed in this section.