Page 172 - Alderney Regional Environmental Assessment of Renewable Energy: Environmental Report

Alderney Regional Environmental Assessment of Renewable Energy:
Environmental Report
5.6.2.6 Loss or changes to foraging grounds
A loss or change in foraging ground such as a reduction in the area or quality for seabirds and
marine mammals has the potential for an associated effect on designated features. Potential
effects are discussed further in each of the specific receptor topic assessments: Ornithology
(specifically Section 5.4.2.5) and Marine Mammals (Section 5.5.2.5). As discussed in these
assessments sensitivity is considered to vary between species. Due to the potential loss of key
foraging grounds sensitivity is considered low to moderate. However any loss of habitat from
individual developments may only constitute a very small fraction of the total area used by a
species for foraging however in the absence of detail on the footprint of the development and
the associated habitat potentially affected and exposure to change is considered to be low to
medium resulting in an insignificant to moderate adverse impact.
5.6.2.7 Non-toxic contamination
Local suspended sediment concentrations (SSC) have the potential to increase during the
construction and decommissioning phases associated with tidal stream turbines, cable routeing
and offshore substations. Such non-toxic contamination has the potential to increase turbidity
and may reduce the foraging ability of marine mammals and seabirds resulting in an associated
effect on a designated feature. Subsequent re-deposition of disturbed sediments may also
result in the smothering of features qualifying for designation, to which benthic species are
considered particularly susceptible. Reference should be made to each of the specific receptor
topic assessments: Water Quality (Section 4.3.2.2), Benthic Ecology (Section 5.1.2.3), Fish and
Shellfish (Section 5.3.2.6), Ornithology (Section 5.4.2.6) and Marine Mammals (Section 5.5.2.6)
for more detail. This assessment considers sensitivity to be low to moderate based on the
varying sensitivity of designated features. Whilst any seabed disturbance will result in
temporary elevated SSC, the extent of the increase is considered to be dependent upon the
superficial sediments and underlying geological properties. The energetic hydrodynamic regime
within the study area means that sediment plumes will be rapidly dispersed. However, it should
be acknowledged that the effects of any elevated SSCs may also have an impact further afield
(e.g. France and the other Channel Islands).
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. Minimal
disturbance to the seabed is anticipated for cable routeing activities given that it is considered
likely that they will be placed directly on the seabed and covered with protection, and therefore
the overall level the exposure to change is negligible to low, resulting in an insignificant to
minor adverse impact.
5.6.2.8 Toxic contamination (sediment release)
Contaminants within seabed sediments may be released during the construction and
decommissioning associated with tidal stream turbines, cable routeing and offshore
substations. Any effects could have an associated impact on designated features. Reference
should be made to each of the specific receptor topic assessments: Water Quality (Section
4.3.2.3), Benthic Ecology (Section 5.1.2.4), Fish and Shellfish (Section 5.3.2.7), Ornithology
R/4001/7 148 R.2129