South Cava Hydrographic and Site Survey Report Xodus AURORA Mainstream Assignment Number: A30082- S00 Document Number: A-30082- S00- REPT- 00- R01 Xodus Group Ltd 8 Garson Place / Stromness / Orkney / KW16 3EE / UK T +44 (0)1856 851451 E info@xodusgroup. com www.xodusgroup. com South Cava Hydrographic and Site Survey Report Xodus AURORA Assignment Number: A30082- S00 Client: Mainstream Document Type: Report Document Number: A-30082- S00- REPT- 00- R01 Date: October 2008 R1 08/10/2008 Issued to SEPA AA LS LS R0 12/08/2008 Issued to client AA LS LS Rev Date Description Issued By Checked By Approved By Client Approval Mainstream – South Cava Hydrographic and Site Survey ii Assignment Number: A30082- S00 Document Number: A-30082- S00- REPT- 00-R01 October 2008 Table of Contents 1 SURVEY DESCRIPTION 1 1.1 Site description and survey programme 1 1.2 Methodology 2 1.2.1 Site survey 2 1.2.2 ADCP hydrographic meter 2 1.2.3 Meteorological station 4 2 SURVEY RESULTS 5 2.1 Bathymetric description of site 5 2.2 Hydrographic data 7 3 HYDROGRAPHIC DATA PLOTS 8 3.1 Time Series of current speed and water depth 9 3.2 Time Series of current direction and water depth 10 3.3 Scatter plot of current speed 11 3.4 Cumulative vector plot for current meter observations 12 3.5 Frequency histogram of current direction 13 3.6 Current speed against percentile 14 3.7 Time- series orthogonal current speed vector component plot. 15 APPENDIX A ADCP SPECIFICATIONS 16 APPENDIX B PITCH, ROLL AND HEADING DATA 24 Mainstream – South Cava Hydrographic and Site Survey iii Assignment Number: A30082- S00 Document Number: A-30082- S00- REPT- 00-R01 October 2008 1 SURVEY DESCRIPTION 1.1 Site description and survey programme A hydrographic and bathymetric survey was undertaken for the proposed salmon farm site off the South coast of Cava in Orkney. The hydrographic and bathymetric survey was undertaken by Xodus Aurora on behalf of Mainstream. The hydrographic survey was conducted between the 9th to the 28th of July 2008 and site survey on the 9th of July 2008. The proposed South Cava salmon farm will consist of 12 circular cages with a 90 m circumference. The salmon farm cages will be arranged in 2 symmetrical lines of 6 cages, arranged in a north west and south east direction. The site centre of the cage group will be 58° 52.281 N 03° 09.530 W ( 333274 E 998797 N). The proposed South Cava site is located in Scapa Flow, approximately 287 m south east of the nearest shoreline of Cava. The proposed site is sheltered by Cava to the north which reaches a height of 36 m. To the south and east the site will be exposed to Scapa Flow in Orkney ( see Figure 1.1) Figure 1.1 Location of the proposed South Cava salmon farm site, Scapa Flow Mainstream – South Cava Hydrographic and Site Survey 1 Assignment Number: A30082- S00 Document Number: A-30082- S00- REPT- 00-R01 October 2008 This report summarises the data collected by current meter measurements and depth position fixing at the Proposed South Cava salmon farm site. The data presented in this report are submitted in support of an application for the consent to discharge from a marine cage fish farm, under the Water Environment ( Controlled Activities) ( Scotland) Regulations 2005, as per SEPA requirements (Annex VIII of SEPA Fish Farm Manual). The following surveys were conducted at the South Cava site. All data collected are contained within this report: Hydrographic survey 9th July 2008 to 28th July 2008 inclusive; and Meteorological survey 8th July 2008 to 29th July 2008 inclusive; and Bathymetric survey 9th July 2008. 1.2 Methodology 1.2.1 Site survey A site survey for the proposed South Cava salmon farm site was undertaken on 9th July 2008 using a depth sounder as per SEPA requirements and in accordance with the AURORA Standard Operating Procedure ( SOP), AE-SOP-005. All depth-sounding positions were determined by Global Positioning System ( GPS) ( see Figure 2.1). The following information was collected on site: Five depth readings at each location; Time and date of readings; and Position fix of reading. All depths were corrected to chart datum using Widewall Bay as the secondary port for tidal correction purposes. Both time and tidal height at 5 minute intervals over the survey period were extracted for Widewall Bay from the Admiralty TOTALTIDE software. Tidal corrections per sounding were achieved by subtracting the interpolation of the tide height increments, with respect to the survey time, from the sounding depth. Interpolation was achieved using EXCEL software. All data were then converted from WGS84 Lat/Long to OSGB36 National Grid using Grid Inquest ( version 5.02). Results of the bathymetric survey are presented in Section 2 of this report. 1.2.2 ADCP hydrographic meter 1.2.2.1 Current meter deployment The South Cava hydrographic survey was undertaken between the 9th July 2008 to 28th July 2008 inclusive, using an RDI 600 kHz Workhorse Acoustic Doppler Current Meter ADCP). The current meter specifications are provided in Appendix A. The ADCP was deployed at position 58° 52.281 N 03° 09.530 W (333274 E 998797 N) as determined by GPS (see Figure 2.1). The ADCP was set up before deployment to take current readings at every 0.5 m increment through the water column with the lowest reading at 2.06 m above the seabed Mainstream – South Cava Hydrographic and Site Survey 2 Assignment Number: A30082- S00 Document Number: A-30082- S00- REPT- 00-R01 October 2008 see Figure A.1 in Appendix A). ADCP set-up including details on blanking distances are provided in Appendix A. Pre-deployment checks of the meter were carried out by Xodus AURORA. The current meter was held in position at the seabed using a weighted, stainless steel frame and gimble. The mooring was positioned where topographic features would not cause spurious data collection for the salmon farm site. The current meter was deployed in a mean water depth of 29.48 m CD within 150 m of the proposed cage group centre ( Figure 2.1). The current meter was preset to collect current speed, current direction and water depth at 20-minute intervals. The ADCP current meter remained at the proposed South Cava salmon farm site for a period of 19 days. This was enough to ensure there was a period of 15 days satisfactory data and the hydrographic survey would not have to be repeated. 1.2.2.2 Current meter retrieval A preliminarily assessment of the data was undertaken when the ADCP current meter was retrieved and it was confirmed that were no anomalies or data gaps present. All raw data files were successfully downloaded by Xodus AURORA and analysis of the data to current SEPA requirements was undertaken by Xodus AURORA. Analysis has been undertaken of pitch, roll and heading readings for the current meter. During this period of the current meter’s deployment there was an alteration in the pitch by < 0.1º, alteration in the roll by < 0.1º and heading by < 0.1º. This indicates that the current meter was in a stable position during the time of deployment ( see Appendix B). This amount of variation is not deemed to have an effect on the data analysed. 1.2.2.3 Current meter analysis Analysis of the 15 day hydrographic data was carried out using data collected between the 10th to the 25th July 2008. This ensured data analysis was based around a 15-day cycle ( half-lunar period) ( see section 2.2). Records 50 to 1115 were taken for analysis purposes. Analysis of the hydrographic data to current SEPA requirements was undertaken by Xodus AURORA. Xodus AURORA Standard Operating Procedure AE- SOP-010 was followed for the interpretation of the hydrographic data, results of which are presented in Section 3 of this report. Mainstream – South Cava Hydrographic and Site Survey 3 Assignment Number: A30082- S00 Document Number: A-30082- S00- REPT- 00-R01 October 2008 1.2.3 Meteorological station Wind conditions at the proposed South Cava site were recorded at the Barrel of Butter 58° 53.42' N, 003° 07.62' W (335145 E 1000880 N) between the 8th July 2008 to 29th July 2008 inclusive. The weather station is located approximately 2.8 km north west of South Cava, in Scapa Flow. The meteorological data (Figure 1.2) for the period of the10th to the 25th July 2008 were taken for analysis to coincide with the period of hydrographic analysis. On analysis it was confirmed that at least 3 consecutive days presented wind speeds of less than 10 m/s (19.3 knots). Results of the survey are contained in the CD accompanying this report. Figure 1.2 Daily wind speed and direction at the Barrel of Butter Weather Station, Scapa Flow. (08/07/2008 until 30/06/2008) 25 200813/ 07/200814/ 07/200815/07/ 07/ 200816/07/ 20 200812/ 07/ 15 200811/ 07/ 10 200810/ 07/ 5 200809/ 08/0 07/ Mainstream – South Cava Hydrographic and Site Survey 4 Assignment Number: A30082- S00 Document Number: A-30082- S00- REPT- 00-R01 October 2008 2 SURVEY RESULTS 2.1 Bathymetric description of site Bathymetric data have been extracted from chart data which extends to cover a 1 km square plot area and will be used for modelling purposes. These data have been supplemented by the following site survey data collected at the site (see Table 2.1 and Section 1.2.1).