|Narrative summary of dataset||A geotechnical survey campaign was undertaken within the vicinity of the Westermost Rough Offshore Wind
Farm. This was supported by a preliminary review of acoustic data and assessment for the presence of Annex I
reefs to minimise the risk of potential damage to protected features.
Following the review of existing data, a drop down video survey protocol was
developed (EMU, 2011) and approved by the Marine Management Organisation (MMO). Part of this protocol
identified that a number of proposed geotechnical sampling sites were likely to be in the vicinity of potential
Annex I reefs and therefore warranted field ground-truthing by means of drop down video to verify the
presence and status of these features. The video ground-truthing survey has now been completed. Drawing upon the findings of this survey, the 2012 EMU report present within this series provides an update of the assessment of the potential Annex I reefs present at the proposed
geotechnical sample locations and fulfils condition 3.1.1 of the Marine Licence (Licence L/2011/001075). The aim of the 2013 Fugro EMU document also present within this series was to satisfy Marine Licence condition 31.22 and to address the responses from
the MMO regarding the Annex I reef features (letter ref: REN024, dated 12th April 2013, and 21st June
2013). The objectives were to assess the impacts (direct and indirect) of the construction activities on
the potential Annex I features.
The objectives of this report were to:
1. Assess the direct impact (loss of habitat) of each of the construction activities;
2. Assess the associated indirect impacts (increase in sediment smothering, and suspended
3. Assess the cumulative impacts of all construction activities.|
|Summary of processing methodology||Two marine vessels were used during the geophysical campaign. At each geophysical site a circle of 50m radius was examined to assess for presence of features. At geophysical survey sites with potential Annex 1 features ground truthing took place using drop down video to assess seabed biological communities, and substrate type.
A total of 31 sites were investigated by Fugro Survey Limited between 12th November and 21st November 2011 inclusive on board the survey vessel MV Flatholm. Photo stills were taken with their accompanied positional fixes for geo-referencing. Full video coverage and at least 5 stills images collected along a 100m transect in the direction of the feature, to confirm extent or proximity of the habitat If no features of interest were found then an additional transect was surveyed perpendicular to the original transect to confirm habitat extent. This maximised the potential to use the information derived from the geophysical data, rather than employing a simple four point (cardinal) survey. A modified approach was employed for the 325m radius circles, as cross transects across the entire sites would not have been practicable, due in part to the anticipated high density of static fishing gear within the area, and tidal constraints. Instead, where features were identified, a single transect crossing either side of the feature was undertaken. The purpose of conducting the drop down video in this way was to confirm the presence of the feature, and also to confirm the absence of Annex I habitat either side of the anticipated feature.
Each stills image collected as part of the seabed video survey was analysed and categorised (no reef, low, medium and high) using the established geogenic reef scoring protocols as described by the EU revised interpretation manual (CEC, 2007) in the EU habitats directive. These categories were then overlain on the existing acoustic data. The video footage was also reviewed to confirm the observations made from the static images and to provide further detail on the qualifying features. The video footage also enabled the extent of the features to be confirmed against the acoustic data and stills image analysis results. Drawing upon the acoustic, benthic and seabed video data, additional potential Annex I features were also interpolated and delineated within the Offshore Wind Farm Area and Cable Route.