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TRANSCRIPT
Site and Hydrographic Survey Report
Aird, Loch Shieldaig
April 2018
Written by: Reviewed by: Approved by: Status:
Date:
Brian Robertson
Penny HawdonMarc Browne
FINAL
30th April 2018
The Scottish Salmon Company8 Melville Crescent
Edinburgh
EH3 7JA
1 Introduction
2 Site description
3 Survey programme3. 1 Current meter set up
3. 2 Weather station set up
3.3 Current meter configuration file
3. 4 Mooring system4 Bathymetry and site survey5 Data processing
5. 1 ADCP data
5. 2 Magnetic heading corrections
5. 3 Hydrographic survey results
5. 4 Summary statistics5. 5 Meterological results
6 Discussion
Annex 1. HG7 analysis summaries
2. ADCP Specification
3. Site map
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INTRODUCTION
This report describes the methods used to collect current speed and direction data
and spot depths at the Aird salmon farm site, and presents the outcomes of the survey.
This deployment was carried out using a Teledyne RD Instruments Acoustic DopplerCurrent Profiler (Sentinel V50 ADCP) mounted in a weighted seabed frame.
Analyses were carried out in accordance with SEPA guidelines ( Regulation andmonitoring of marine cage fish farming in Scotland - a procedures manual. AttachmentVIII Site and Hydrographic Survey Requirements. Version 2. 7, 315' October 2008).
2 SITE DESCRIPTION
The hydrographic survey site is located on the west side of Loch Shieldaig, within LochTorridon at the north side of the existing Scottish Salmon Company ( SSC) Aird farmsite. There were 10 cages on site at the time of survey. Within the survey area theseabed slopes eastwards to water depths > 50m. There is an area of very shallowwater (' Dora Rock') in the southern part of the survey area.
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Figure 1: Location of Aird, Loch Shieldaig
The Scottish Salmon Company 2018
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3 SURVEY PROGRAMME
3.1 Current meter setup
The ADCP deployment position was ( WGS84) 57132. 585' N 005a41. 740' W ( NG 78934
56351) which is 170m from the new proposed site centre for Aird. Detailed
specifications for the ADCP are located in the Annex 2.
The hydrographic data collection period was from 10th July 2017 to 10th August 2017. A half -lunar 15 -day period of data was analysed for this report; from 19th July 2017 to3`d August 2017. Positioning forthe survey was provided by GPS and compatible chartplotter as installed on the SSC landing craft and was backed up using a Garminhandheld GPS with minimum 8 satellite coverage.
3. 2 Weather station set up
Meteorological data was obtained from the Gairloch weather station at ( WGS84)
57043. 867' N 005041. 933' W ( NG 79884 77276), approximately 20km due north of thesite. The data was provided via the website www.wunderoround. com
3. 3 Current meter configuration file
Table 1: Sentinel V50 ADCP configuration files
ADCP model Sentinel V50
ADCP serial number 24476
Number of cells 37
Cell size m 1. 2
First cell centre range m 2. 47
Start date and time UTC 10/ 07/ 2017 16: 00
Time between ensembles minutes 20
Ping interval seconds 1
Number of pings 300
Transducer orientation U
Magnetic variation 0
Cell Standard Deviation cm/s 0. 33
Instrument std.dev [for 1. 2m cells] (cm/s) 5. 716
The ADCP was configured at the time of deployment having established the waterdepth and expected tidal range on site. This was carried out on the instrument settings
using a laptop with wireless connectivity.
The Scottish Salmon Company 2018
3.4 Mooring system
The ADCP was fixed in a gimballed, weighted sea bed frame. The head of the ADCPwas 0. 5m from the seabed throughout the deployment. Internal parameters for pitch,
roll and heading were checked post -deployment to ensure a stable position wasmaintained throughout.
4 BATHYMETRY AND SITE SURVEY
A full bathymetric survey was carried out using a Garmin portable chart plotter withacoustic sounder on 18th October 2017. Boat GPS was used at the start of the surveyto verify accuracy to return positional information ( WGS84). Both devices received aminimum of 8 satellite coverage throughout the survey. Recorded depths werecorrected to Chart Datum ( CD) using Admiralty Total Tide software and referencedagainst tide predictions for the secondary port Shieldaig. The bathymetric surveyconcluded that chart data was reliable throughout the development area.
The bathymetry plot and selected depth soundings are provided below:
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Figure 3: Bathymetric plot
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Table 2: Bathymetric data
Sounding
GPS Position Time
UTC)
Measured
depth ( m)
Tide
height ( m)
Corrected
depth ( m) Latitude ( N) Longitude ( W) Eastings Northings
A 57- 32. 700 005- 41. 714 178972 856564 1232 46. 58 1. 31 45.27
B 57° 32. 621 005- 41. 867 178811 856425 0928 9.84 2. 90 6. 94
C 67- 32. 624 005- 41. 789 178889 856426 1231 28. 32 1. 31 27. 01
D 57° 32. 629 005° 41. 657 179022 856429 0954 55.64 2. 40 53.24
E 57° 32. 636 005° 41. 538 179141 856434 0953 80. 50 2. 40 78. 10
F 57- 32. 527 005- 41. 828 178840 856249 0956 32. 33 2. 40 29.93
G 57° 32. 538 005° 41. 712 j 178957 856263 1203 39.66 1. 19 38.47
H 57- 32. 547 005- 41. 659 179011 856277 1203 49. 95 1. 19 48. 76
I 57° 32. 435 005° 41. 826 178833 856076 0957 34. 20 2. 40 31. 80
J 57° 32. 438 005° 41. 653 179006 856075 1141 39.77 1. 20 38. 57
K 57° 32. 495 005- 41. 440 179224 856169 1143 59. 49 1. 20 58. 28
L 57° 32. 335 005° 41. 834 178815 855893 0912 16. 77 3. 07 13. 69
M 57° 32. 334 005° 41. 776 1178873 855887 0958 13. 87 2. 40 11. 47
N 57° 32. 322 005- 41. 652 178995 855858 0959 24.36 2. 40 21. 96
O 57° 32. 331 005° 41. 397 179251 855862 1000 70. 85 2. 24 68. 61
P 57° 32. 221 005- 41. 738 178900 855675 1119 3. 46 1. 36 2. 10
DATA PROCESSING
5.1 ADCP data
Data was extracted from the ADCP by downloading to laptop wirelessly. From therethe data was extracted to a bespoke programme ' Velocity' for processing, then laterto Excel.
SEPA specifies that data should be presented for specific depths, therefore the data
was selected against the following requirements;
Sub -surface - from a depth 5m below the lowest predicted spring tide during thedeployment period
Cage -bottom - at a depth corresponding to the bottom of the cages at mean sealevel t 1 m
Near -bottom - as close to the bed as practicable
Mean tidal height recorded by the ADCP during the deployment was 31. 55m from theseabed, with a minimum tidal height for the deployment of 28. 76m. Cage depth wasassumed to be 10m.
Near -bottom, cage -bottom and sub -surface depths were taken at distances of 2. 97m,
19. 77m and 24. 57m respectively from the sea bed.
The Scottish Salmon Company 2018
Table 3: Deployment depth details
Hydrographic data were analysed using the SEPA tool HGdata_ analysis_ v7, runningin Excel. HG7 data summaries can be found in the Annex.
Pre- and post - deployment values were rejected from the dataset, restricting thedataset to 1081 records.
Data quality was confirmed by calculation of the standard deviation ( std. dev) at eachof the chosen depths cells using the exported ' Percent Good' data from Velocity. Thecalculated std. dev was then compared against the expected cell std. dev ( in this case0. 33 cm/ s) and confirmed to fall within the SEPA guideline of 2 cm/ s.
Percent Good' is the percentage of valid pings used to calculate the std. dev. In thiscase, the exported data used is PG1 ( percent of good data computed from 3 beams)
and PG4 ( percentage of good data from 4 beams) from the meter to calculate thestd. dev as follows:
Cell std. dev = Instrument std. dev / q [ no. of pings x { ( PG1 + PG4) / 100 ) ]
The Cell std. dev for surface, mid and bed cells all calculated out as 0. 33 cm/ s,
indicating the data set was of an extremely high quality.
5. 2 Magnetic heading corrections
A Grid Magnetic Angle of 0. 5580W ( from http:// www. geomag. bgs. ac. uk/
The Scottish Salmon Company 2018 H
Measured depth at deployment 31. 11 m
Predicted tidal height at deployment
from Admira ty tide tables2. 70m
Corrected depth at deployment (CD) 28. 41 m
Lowest predicted tide during deployment 0. 40m
Charted mean sea level ( range) 5. 40m
Average tidal height 3. 10m
Mean sea level height above bed ( MSL) 31. 51 m
Assumed cage depth 10. 00M
ADCP mooring height 0. 50m
Mean ADCP recorded pressure incl. height 31. 55m
Mean cell height above seabed
Surfacecell
Mid cell
Bed cell
24. 57m
19. 77m
2. 97m
Mean cell depth below Chart Datum depth
Surface cell
Mid cell
Bed cell
3.84m
8. 64m
25. 44m
Hydrographic data were analysed using the SEPA tool HGdata_ analysis_ v7, runningin Excel. HG7 data summaries can be found in the Annex.
Pre- and post - deployment values were rejected from the dataset, restricting thedataset to 1081 records.
Data quality was confirmed by calculation of the standard deviation ( std. dev) at eachof the chosen depths cells using the exported ' Percent Good' data from Velocity. The
calculated std. dev was then compared against the expected cell std. dev ( in this case0. 33 cm/ s) and confirmed to fall within the SEPA guideline of 2 cm/ s.
Percent Good' is the percentage of valid pings used to calculate the std. dev. In thiscase, the exported data used is PG1 ( percent of good data computed from 3 beams)
and PG4 ( percentage of good data from 4 beams) from the meter to calculate thestd. dev as follows:
Cell std. dev = Instrument std. dev / q [ no. of pings x { ( PG1 + PG4) / 100 ) ]
The Cell std. dev for surface, mid and bed cells all calculated out as 0. 33 cm/ s,
indicating the data set was of an extremely high quality.
5. 2 Magnetic heading corrections
A Grid Magnetic Angle of 0. 5580W ( from http:// www. geomag. bgs. ac. uk/
The Scottish Salmon Company 2018 H
dataservice/ charts_ navig/ gma_ calc. html) was applied and grid convergence ( fromHGd_ata_ analysis_ v7) was 3. 120°W to give an overall declination of - 3.6780.
Table 4: Magnetic heading corrections
Date I Lat
I Long I NGR_X NGR_Y mag. dec I grid conv. I GMA19/ 07/ 2017 55°42. 931N 005042. 577W 1 178934 856351 3. 678%N 3. 120° W 0. 558- W
N otes:
positions recorded to WGS84, and converted to OSGB36 using OSTN97
magnetic declination from US- NOAA Geomagnetism website
grid convergence from OS corrections tool
grid magnetic angle = magnetic declination - grid convergence
5. 3 Hydrographic survey results
Pitch, roll and heading exhibited very slight variations during the deployment from - 2. 15° to - 1. 640, 2. 520 to 2. 630 and 47. 010 to 48. 900 respectively. These results arewithin acceptable limits for the instrument and indicate a stable deployment.
The data quality calculation is described in section 5. 1, and verifies that data isof goodquality.
Data cells representative to bed, cage depth and sub -surface were extracted from the
data set using Velocity. A summary of processed statistical data is provided in Table5.
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5.4 Summary statistics
Table 5: Summary statistic table
The Scottish Salmon Company 2018
Bed Mid SurfaceNo. of records 1081 1081 1081
Start date / time UTC 19/ 07/ 1711: 00 19/ 07/ 1711: 00 19/07/ 17 11: 00End date/ time 03/ 08/ 1711: 00 03/ 08/ 1711: 00 03/ 08/ 17 11: 00
Mean velocity m/s 0. 062 0. 107 0. 111
Minimum velocity m/ s 0. 000 0. 001 0. 002
Maximum velocity( m/ s 0. 451 0. 480 0.499
Ranked % of mean velocity 71 64 64
Ranked % of 3 cm/ s 46 19 15
Ranked % of 4. 5 cm/ s 60 29 26
Ranked % of 9. 5 cm/ s 81 58 58
Residual velocity m/ s 0.040 0. 067 0. 072
Residual direction OT 003 344 343
Major axis OT 355 345 355
Residual parallel m/s 0. 039 0. 067 0.070
Residual normal m/ s 0.005 0. 001 0.015Amplitude parallel m/ s 0. 113 0. 147 0. 144
Amplitude normal m/ s 0. 050 0. 092 1 0. 105
Amplitude anisotropy 2. 26 1. 60 1 1. 37
The Scottish Salmon Company 2018
5. 5 Meteorological results
The data from the weather station deployed at Gairloch was analysed using the SEPAtool HGdata_ analysis_ v7. HG7 data summaries can be found in Annex 1.
The data from this weather station exhibits no recorded wind speeds in excess of10m/ s.
Mean wind speed over the whole deployment was 2.5m/s. The deployment period
therefore met the requirement of mean daily wind speed < 10m/ s.
DISCUSSION
Observed depth data sets were shown to be consistent with charted depths.
Pressure and altitude records showed no evidence of problems with the deployment
such as mooring dragging or excessive movement of the seabed mooring frame. Thetidal height range and time series are consistent with predicted tidal heights.
In general, the site was characterised by moderate/ strong tidal energy. Surfacevelocity was found to be almost double the bed velocity. Surface, cage depth and bedcell current directions were all observed to dominate in a north to north- north- west
direction. Velocities were moderate/ strong, with a maximum recorded velocity of 0.499m/ s.
The re -suspension threshold of 9.5cm/ s was exceeded 19% of the time for the near -
bed data. The site is therefore likely to experience re -suspension and may result inmoderate export of released solids in AutoDepomod modelling. Velocity and directionshowed clear 12. 5h periodicity at all depths; and velocity showed clear spring neapvariation.
Current directions were parallel to bathymetric contours and would correspond with
prospective cage layout running parallel to the shoreline. Residual current vectorswere orientated north at bed cell and towards north- north-west for the cage depth andsurface cells.
Meteorological data shows no major effect on the surface current.
Overall, the recorded data are indicative of a moderately flushed site and is consideredsuitable for development in terms of hydrography and bathymetry.
This dataset is considered to provide a good basis for AutoDepomod modelling.
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ANNEX 2 ADCP Specification
Depth Cell Sim'
Depth Ceti Sim'
0. 25m
0. 3m0. 5m
Loin20m4. Om6.OmCommvmunmm and Rerwding WirelessInternal memoryRoble paramrtert Velocity accuracy
Fara hrcensnY Profile
Transdowr and Nirdware
Standard Sensors
power
Sofrnare
Velocity resolutionVelocityrarge
ping rate
Vertnat resolution
Dynamic range
Recision
Beam angleCanfiguationDepth ratingMaterials
V20( 100DFIh) V50( SODIdtr) VI00( 300k1tr)
Ragelmyr Std Dev( crNsy' Range( my' Std Deviantsµ' Range ( my I Std Dev( erNsy' Wide/ Hanov, Wide/ Narrov Wide/ Nanow Wide/ Namwv, wde/Naraw Wide/ Narrow
18.0/ 12.6 19. 2/ 36. 5
193/ 140 11./ 208201/ 24.9 71/ 13. 4 44. 1/ 576 19.2/ 36. 512. V26. 9 36/ 6. 7 50. 5/ 64. 6 71/ 13. 5 94. 51120. 6 109/ 20. 624. 5/ 29.4 17/ 3. 2 56.07106 3. 6/6. 7 1035/ 130.4 5. 5/ 10. 3269/ 320 0. 8/ 16 63. 1/ 78. 1 17/ 31 114. 6' 142. 3 27/ 5. 2
674/818 1. 112. 1 121, 7/ 151. 5 1. 8/ 3. 3
Temperature pmweed on trmea seqCOWS lmgOerPIOOICIhR SeInIXITilt tmEmsar Naomatm)
Pressure senior (mounted on transducer)
External DC inert
Imemalbatteryvaltage
Battery caps ty; over- the- counter @O' CBattery pack @5° C
Teledyne RDI' s new software included
01. 11b/ gyn
One 1606 Micm SD Card included
V201V50: 0 5% of the water velocity relative to the ADCP = 0. 3crrys11100: 05% of the water velocity relative to the ADCP 10 Santis
O. lcmVsSnVs ( defau1t512( hMs (maxim iiiUp is 4112
Depth tell size
8OdB1 Still25•
4beancomex; Sth beam vertical
200MTransducer, hauvng, and end cap: plasticConnector metal sbe0
Range - 5° to 45° C, praisisn * A- C, resolution 0. 1 -
Accuracy 2' AMS. resolution 0 V, maxdip angle 85' Pitch range 190'. roll range 1180°, acuraq 2' RMSpredskm DOS' RMS, resolution O V
Range 300nc accuracy Ol%FS
12- 20VDC181/0( new100 wan hours pypltnl)
SIO wart hours
Ready/ - Pre - deployment Oesting. planning, and data recovery) ` Velocity - Poor processing ( data handing. display. and export)"
Eonmiuremal Standard depth rating 200m
Operating temperature . 5* m 45- CStorage temperature 04irMm Mnnes) - So' to 60'( Weight in air 7Skg - 16.OkgWeight in water 1. 6kg- 6Okg
Available Optiom External battery cameAC/ DC power convener • Rh beam ( at time of order only) • Waves pmcessirg • Straight or right angle metal shell connettpr
Daemion, Special configuration drawing available upon request
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