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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7 Gaps in underst<strong>and</strong>ing<br />
Research for this report has highlighted a number <strong>of</strong> gaps in available data<br />
<strong>and</strong> in underst<strong>and</strong>ing <strong>of</strong> the actual impacts resulting from cable burial activities<br />
associated with the <strong>of</strong>fshore wind farm industry. The general lack <strong>of</strong> underst<strong>and</strong>ing<br />
is due to the physical <strong>and</strong> biological effects <strong>of</strong> cable burial being very site<br />
specific, particularly with regard to sites with different sediment characteristics.<br />
What makes this even more difficult to interpret is that the majority <strong>of</strong> sites will<br />
experience a large variation <strong>of</strong> sediment types along the cable routes. There has<br />
also been a deficit in the monitoring <strong>of</strong> cable burial activities in the past as the<br />
impacts are regarded as secondary in terms <strong>of</strong> scale when compared with those<br />
from the installation <strong>and</strong> operation <strong>of</strong> the wind turbines.<br />
There is limited centralised knowledge sharing both with the <strong>of</strong>fshore wind farm<br />
industry <strong>and</strong> from other more established marine cabling industries such as<br />
subsea telecommunications <strong>and</strong> the oil <strong>and</strong> gas sector. Information that does<br />
exist is not widely disseminated, reviewed or synthesised for a wider audience<br />
or made publicly available.<br />
There is limited documentation <strong>and</strong> research carried out to date on the<br />
quantification <strong>of</strong> material disturbed <strong>and</strong> brought into suspension from cable<br />
burial operations, in particular, from burial methods using jetting, cutting,<br />
dredging <strong>and</strong> excavating tools. This lack <strong>of</strong> basic information on the volumes <strong>of</strong><br />
sediment brought into suspension limits the potential <strong>of</strong> modelling techniques<br />
<strong>and</strong> establishing the fate <strong>of</strong> sediment plumes. Research from other industries<br />
can be used for predicting potential effects but the scale <strong>of</strong> impacts is quite<br />
different (as identified in Section 4.4) <strong>and</strong> the effect will depend on the sensitivity<br />
<strong>of</strong> the receptor <strong>and</strong> the site conditions. Should the generation <strong>of</strong> a sediment<br />
plume be considered to be an area <strong>of</strong> concern, in situ monitoring <strong>of</strong> a number<br />
<strong>of</strong> different techniques <strong>and</strong> tools in one location, together with further plume<br />
modelling would be required in order to draw comparisons under the same site<br />
specific conditions. Confidence in the modelling could be attained by comparing<br />
predicted versus in situ results. The sediment monitoring requirements included<br />
in FEPA licences for UK Round 1 <strong>and</strong> potentially Round 2 <strong>of</strong>fshore wind farm<br />
applications will also provide valuable data for the quantification <strong>of</strong> the impact<br />
<strong>of</strong> cable burial operations.<br />
In addition, there is a general lack <strong>of</strong> underst<strong>and</strong>ing <strong>of</strong> the biological response<br />
to sediment plumes, arising from any activities that disturb the seabed, such<br />
as the sensitivity <strong>and</strong> tolerance <strong>of</strong> species <strong>and</strong> habitats to different levels <strong>of</strong><br />
sediment plumes <strong>and</strong> different plume durations. Additional research in this area<br />
is therefore necessary in order to further this knowledge base to enable accurate<br />
predictions <strong>of</strong> sensitivity to be determined. There are, however difficulties in<br />
undertaking research to fill these gaps such as the problem associated with<br />
site specific differences changing the scale <strong>of</strong> the effects <strong>and</strong> the adaptability <strong>of</strong><br />
species in different environments <strong>and</strong> at different times <strong>of</strong> the year. Targeted<br />
research involving the testing <strong>of</strong> different cable burial devices <strong>and</strong> tools in the<br />
same conditions (seabed types, wave <strong>and</strong> tidal conditions) could overcome<br />
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