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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5.3.2 POTENTIALLY SIGNIFICANT EFFECTS<br />
Seabed disturbance<br />
Potential impacts <strong>and</strong> mitigration measures<br />
Construction activities leading to disturbance will include provision <strong>of</strong> access<br />
for equipment <strong>and</strong> any specific preparations that may be necessary, such as<br />
the placement <strong>and</strong> excavation <strong>of</strong> anchors to assist the cable installation barge;<br />
construction <strong>of</strong> jointing chambers, removal <strong>of</strong> structures such as concrete facings<br />
on sea walls, breach <strong>of</strong> sea defence structures <strong>and</strong> excavation <strong>of</strong> trenches to the<br />
jointing chamber.<br />
Disruption to intertidal habitats will occur within the construction corridor. The<br />
magnitude <strong>of</strong> direct disturbance is likely to be similar for all installation techniques<br />
(i.e. width <strong>of</strong> trench created) but will vary with width <strong>of</strong> the shore (see Section<br />
5.2.2). The significance <strong>of</strong> the impact will largely depend on the environmental<br />
sensitivity <strong>of</strong> the area affected <strong>and</strong> is based on the following parameters:<br />
●<br />
●<br />
●<br />
Habitat type <strong>and</strong> overall distribution within the localised area <strong>and</strong> wider<br />
environment;<br />
Recoverability <strong>of</strong> habitat <strong>and</strong> species;<br />
Importance <strong>of</strong> the habitat/species (i.e. protected status);<br />
● Use <strong>of</strong> the area for feeding <strong>and</strong>/or roosting birds (see also Section 5.7); <strong>and</strong><br />
●<br />
Use <strong>of</strong> the area for fish spawning, nursery <strong>and</strong>/or feeding grounds (see also<br />
Section 5.4).<br />
Intertidal habitats that are more sensitive to the impacts <strong>of</strong> cable burial are<br />
generally those that have established in more sheltered conditions, where<br />
natural perturbations are lower <strong>and</strong> less frequent. Such habitats include<br />
saltmarsh, mudflats, muddy gravel, bedrock, biogenic reef <strong>and</strong> eel grass beds.<br />
These habitats, in general take longer to recover from disturbance compared to<br />
those which are more dynamic <strong>and</strong>/or frequently disturbed such as s<strong>and</strong> flats,<br />
shingle beaches <strong>and</strong> mixed sediment habitats. Such dynamic habitats are likely<br />
to support a different assemblage <strong>of</strong> species which are better adapted to <strong>and</strong><br />
more tolerant <strong>of</strong> frequent, short term disturbance, such as occurs naturally <strong>and</strong><br />
is associated with cable installation.<br />
The sensitivity <strong>of</strong> the intertidal environment can also display distinct temporal<br />
patterns, associated with seasons. Examples include use <strong>of</strong> the site by wading<br />
waterbirds <strong>and</strong> wildfowl during the over-wintering period (see Section 5.7),<br />
or being <strong>of</strong> seasonal importance to important life stages <strong>of</strong> fish <strong>and</strong> shellfish<br />
species (see Section 5.4).<br />
Sediment mobilisation<br />
In addition to direct disturbance, there are also issues relating to sediment<br />
mobilisation across the intertidal area. Cable installation within the intertidal<br />
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