Table 5 Example impact assessment matrix Sensitivity High
Medium Low
Negligible Magnitude High
Major Major
Moderate Minor
Worked example 11.
The worked example provided below is for the smothering of Sabellaria spinulosa during construction. The EIA will consider the impacts of smothering of all relevant species and habitats, however to keep this example short and concise only S. spinulosa has been considered. Please note this is a theoretical example of how the definitions and matrices will be used and in no way represents the final EIA assessment which will be further refined by amongst other things the results of the Physical Processes assessments.
12.
There is potential for the following construction activities to increase suspended sediment and therefore impact upon S. spinulosa through smothering:
Seabed preparation for foundations; Jack up barge feet placement; and Cable laying activities
13.
Research has shown that S. spinulosa has limited or no sensitivity to smothering (Last et al. 2011; Jackson and Hiscock, 2008) and that the species is able to recover quickly from such events. Therefore, the sensitivity of this species to smothering is considered to be negligible.
14.
Within the cable route the biotope SS.SBR.PoR.SspiMx (S. spinulosa on stable circalittoral mixed sediment) was identified. This biotope is of importance as it has the potential to contain Annex 1 Habitat in the form of biogenic reef. Due to its designation as an Annex 1 habitat S. spinulosa reef is considered to be of high value.
15.
Low numbers of S. spinulosa were found within the East Anglia THREE site with no indication of the presence of reef forming aggregations. Slightly larger numbers of S. spinulosa were found within the cable route and the presence of the biotope SS.SBR.PoR.SspiMx indicates reef forming potential. The temporary impacts associated with cable burial within the cable route and smothering within the East
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Appendix. 10.1 Benthic Ecology Evidence Plan Page 31
