Page 101 - Alderney Regional Environmental Assessment of Renewable Energy: Environmental Report

Alderney Regional Environmental Assessment of Renewable Energy:
Environmental Report
shellfish and fish species to this impact pathway is species dependent and overall is
considered to be low to moderate. The probability of substantial spillage occurring and the
overall level of exposure to change is considered to be negligible to low for all phases and
developments, resulting in an insignificant to minor adverse impact. In the unlikely event of
an incident, best practice measures put in place to manage potential water quality impacts (see
Section 4.3.2.1), such as the use of oil spill action plans, would contain the spillage and prevent
substantial effects.
5.3.2.5 Changes to/loss of habitat
As discussed in benthic ecology (Section 5.1.2.2) habitats are sensitive to a direct physical loss
and/or damage where permanent or temporary structures are introduced within the
development footprint. Any effect could indirectly affect fish and shellfish such as through loss
of feeding and nursery areas. However, fish species are typically highly mobile and it is
considered they can utilise alternative food sources or sheltered areas should they need to
move to new foraging/nursery grounds and, therefore, the sensitivity of fish to a change in
habitat is considered to be low. In general, the mobility of shellfish species is reduced
compared to fish and, therefore, they are considered to have a moderate sensitivity.
The effects arising are dependent on a range of factors such as the habitat type, the extent of
habitat affected, the location and the nature of activities and whether they are temporary or
permanent. Given that the marine and intertidal habitats that are found in Alderney’s waters
are widespread, and the overall footprint of change on the seabed is considered to be relatively
minor, the exposure to change is considered to be low, resulting in an insignificant to minor
adverse impact.
5.3.2.6 Non-toxic contamination
As outlined in Section 4.3.2.2, in areas being excavated or disturbed for the installation/removal
of tidal stream turbines, cables or offshore substations there will be an increase in SSC.
Increased SSC has the potential to affect fish behaviour species. The increased SSC may also
impact shellfish through smothering or a reduction in food availability in the water column.
Conversely, disturbance of the seabed may increase ambient nutrient levels which, in turn,
could lead to an elevated food supply. The sensitivity of fish to this impact pathway is
considered to be low given their high mobility whereas the sensitivity of shellfish is considered
to be moderate.
For tidal stream turbines and offshore substations, the overall level of exposure to change is
considered to be low, resulting in an insignificant to minor adverse impact. The cables are
likely to be buried in soft sediment areas and placed directly on the seabed and covered with
protection in areas where the cable cannot be buried. Overall, therefore, the level the exposure
to change is negligible to low, resulting in an insignificant to minor adverse impact.
5.3.2.7 Toxic contamination (sediment release)
There is potential for toxic contaminants to be released into the marine environment as a result
of the disturbance of contaminated sediments during construction and decommissioning of all
R/4001/7 77 R.2129