b3408a2d-0ef5-41ba-a471-f6b91c435f45 eng G2467_SSS series ABP Marine Environmental Research Ltd 02380711840 Quayside Suite, Medina Chambers, Town Quay Southampton SO14 2AQ United Kingdom enquiries@abpmer.co.uk http://www.abpmer.co.uk pointOfContact 2021-03-08 MEDIN Discovery Profile 2.3 urn:ogc:def:crs:EPSG::32631 2020, Fugro, Sheringham Shoal Offshore Wind Farm, Seabed Monitoring Survey 2014-03-05 publication 2012-10-08 G2467_SSS Equinor UK Ltd contracted Fugro GB Marine to undertake a Geophysical Survey of UK North Sea, located 23 KM off the North Norfolk coast. The survey comprised of the collection of multibeam bathymetry, multi beam backscatter data and side scan sonar data. The aims of the seabed survey 2020 were as follows; ◼ Acquisition of MBES, MBBS and SSS data around 88 wind turbine generators (WTG), 2 offshore substation (OSS) locations and export cable route (ECR) route; ◼ Identify sediment scouring, seabed contacts and features and cable free spanning across both survey sites; ◼ Compare survey results with 2018 survey findings and interpretations. The main findings arising from the geophysical survey data can be summarised as follows: ◼ Seabed depths on the main turbine array site (excluding monopiles and areas of rock dump) ranged from 14.54 m to 23.66 m below LAT; ◼ Seabed depths observed on the export cables ranged from 3.19 m to 24.40 m below LAT; ◼ A total of 24 exposures were identified; 15 located on the main site and 9 located on the export cable route; ◼ On the main site, the 15 exposures were located on the inter-array cable routes C2-D2, K8-J8, K7-J7, and adjacent to the WTG locations K8, J8, J7, I7, H6, G6, F6 and G5; four exposures showed evidence of freespan; ◼ One exposure was identified on the export cable route B in the southern end of the site; this was 9.6 m in length. Two further sets of exposures were observed in the export cable survey area, believed to relate to the Stratos Telecom cable and another possible unknown cable; ◼ In total 2056 SSS contacts were identified. Of those 801 were found on the main site and 1255 on the export cable route; ◼ Eight wrecks were identified on the wind farm site and the export cable route. The Crown Estate +44 020 7851 5000 1 St James Market London SW1Y 4AH United Kingdom enquiries@thecrownestate.co.uk http://www.thecrownestate.co.uk custodian Fugro +44 (0)2392 205500 Victory House,Trafalgar Wharf (Unit 16) Portsmouth Hampshire PO6 4PX United Kingdom unknown www.fugro.com originator asNeeded Side-scan sonar SeaDataNet Parameter Discovery Vocabulary 2018-09-07 revision 109 Bathymetry and Elevation SeaDataNet Parameter Discovery Vocabulary 2018-09-07 revision 109 Offshore Cable Corridor The Crown Estate Renewable Energy Development Areas 2012-05-15 revision 1 Renewable Energy Lease area The Crown Estate Renewable Energy Development Areas 2012-05-15 revision 1 Post-Construction monitoring The Crown Estate Renewable Energy Development Phases 2012-05-15 revision 1 Offshore Substation The Crown Estate Renewable Energy Development Areas 2012-05-15 revision 1 Marine Environmental Data and Information Network Marine Environmental Data and Information Network No restrictions intellectualPropertyRights intellectualPropertyRights No restrictions 1 eng elevation geoscientificInformation 0.828491 1.231625 52.948708 53.182847 2020-11-24 2020-12-29 series The Starfix primary positioning system worked well throughout the survey with no prolonged drop-outs. Vessel positioning was of high quality and within the limits specified in the contract. Further postprocessing within Fugro Starfix VBA Proc software ensured that all position data were within specification and accurately reduced to LAT. The bathymetry data collected were of good quality. Any obvious noise present in the data was removed and the remaining data were corrected for variations in positioning quality and corrected for sound velocity where required. Following processing, bathymetric sounding. standard deviation values were also assessed to ensure that data were consistent, vertically aligned and no erroneous soundings were present. Bathymetric differences were assessed between the winter 2020 survey and the autumn 2018 surveys. The checks were conducted on regions of flat seabed throughout the ECR and main array sites where no visible effects from construction or sand dune migration were evident. The rationale behind this was that these areas would be subject to the least change over time, meaning positional checks can be relied upon without the possibility of large amounts of natural change in the seabed skewing the results. In these regions, vertical differences were typically less than less than 0.15 m. This check provided further confidence that the datasets were correctly positioned and of high accuracy. SSS data were initially acquired using the Edgetech 4205 SSS (230/540/850 kHz), however, it was noticed that the data collected were excessively stripy and stretched. The Edgetech 4205 was therefore replaced with the Edgetech 4200 and the acquisition completed with it, although the same data quality issues were still partially present. This was assessed to be the results of strong currents in the area. Figure 4.1 and Figure 4.2 below show a comparison between data quality at low currents and data quality at high currents. The SSS data were deemed to be of overall good quality and fit for purpose. Detection of small objects such as fishing gear pots (less than 0.5 m in length), the ropes connecting them (less than 0.1 m in diameter) and cable exposures, were successfully achieved across the main site and on the export cable route. The presence of fishing gear and depth limitations in the nearshore area of the cable route area meant that full side scan sonar coverage could not be attained. However, only small gaps were present due to these limitations and were instead covered with multibeam backscatter. https://www.marinedataexchange.co.uk/details/1986/summary A link to the web service or dataset. https://www.marinedataexchange.co.uk A link to the general host site.