10.1.3.2 Vessel Draught
A plot of all vessel tracks (excluding temporary traffic) recorded within the Proposed Development array area shipping and navigation study area throughout the survey periods, colour-coded by draught, is presented in Figure 10.21 Open ▸ . Following this, the distribution of these draught classes by survey period is presented in Figure 10.22 Open ▸ .
Figure 10.21 Vessel Traffic Movements within Proposed Development Array Area Shipping and Navigation Study Area by Vessel Draught (28 Days Summer 2022 and Winter 2021)
Figure 10.22 Vessel Draught Distribution within Proposed Development Array Area and Shipping and Navigation Study Area (28-Days Summer 2022 and Winter 2021)
Vessel draught was available for approximately 67% of vessels recorded in the Proposed Development array area shipping and navigation study area throughout both survey periods and ranged from 1.2 m for a wind farm support vessel to 20 m for a crude oil tanker.
Excluding the vessels for which a draught was not available, the average draught of all vessels within the Proposed Development array area shipping and navigation study area throughout the summer and winter survey periods was 5.2 m and 5.8 m, respectively.
10.1.4 Anchoring Activity
Anchored vessels can be identified based upon the AIS navigational status which is programmed on the AIS transmitter on board a vessel. However, information is manually entered into the AIS, and therefore it is common for vessels not to update their navigational status if only at anchor for a short period of time.
For this reason, those vessels which travelled at a speed of less than 1 kt for more than 30 minutes had their corresponding vessel tracks individually checked for patterns characteristic of anchoring activity. After applying these criteria, no vessels were deemed to be at anchor within the Proposed Development array area shipping and navigation study area.
10.2 Proposed Development Export Cable Corridor
A number of tracks recorded during the Proposed Development export cable corridor survey periods were classified as temporary (non-routine), such as the tracks of non-routine survey vessels and vessels associated with the construction of NnG. These have therefore been excluded from the analysis.
A plot of the vessel tracks recorded during a 14-day survey period in July 2020, colour-coded by vessel type and excluding temporary traffic, is presented in Figure 10.23 Open ▸ . A plot of the vessel tracks recorded during a further 14-day survey period in January 2021, colour-coded by vessel type and excluding temporary traffic, is presented in Figure 10.24 Open ▸ .
Figure 10.23 Vessel Traffic Movements within Proposed Development Export Cable Corridor Shipping and Navigation Study Area by Vessel Type (14 Days Summer 2022)
Figure 10.24 Vessel Traffic Movements within Proposed Development Export Cable Corridor Shipping and Navigation Study Area by Vessel Type (14 Days Winter 2021)
Plots of the vessel tracks for the summer and winter survey periods converted to a density heat map are presented in Figure 10.25 Open ▸ and Figure 10.26 Open ▸ , respectively.
Figure 10.25 Vessel Density Heat Map within Proposed Development Export Cable Corridor Shipping and Navigation Study Area (14 Days Summer 2022)
Figure 10.26 Vessel Density Heat Map within Proposed Development Export Cable Corridor Shipping and Navigation Study Area (14 Days Winter 2021)
10.2.1 Vessel Counts
For the 14 days analysed in the summer survey period, there was an average of 29 unique vessels per day recorded within the Proposed Development export cable corridor shipping and navigation study area. In terms of vessels intersecting the Proposed Development export cable corridor itself, there was an average of 25 unique vessels per day.
The daily number of unique vessels recorded within the Proposed Development export cable corridor shipping and navigation study area and the Proposed Development export cable corridor itself during the summer survey period are presented in Figure 10.27 Open ▸ . Since the survey commenced and concluded midway through the first and last days of the summer survey period (as described in section 5.2), the first and last days are partial.
Figure 10.27 Unique Vessels per Day within the Proposed Development Export Cable Corridor Area and Shipping and Navigation Area (14 Days Summer 2022)
Throughout the summer survey period approximately 87% of unique vessel tracks recorded within the Proposed Development export cable corridor shipping and navigation study area intersected the Proposed Development export cable corridor itself.
The busiest day recorded within the Proposed Development export cable corridor shipping and navigation study area throughout the summer survey period was 4 August when 39 unique vessels were recorded. The busiest day recorded within the Proposed Development export cable corridor itself throughout the summer survey period was 5 August when 34 unique vessels were recorded.
The quietest full day recorded within the Proposed Development export cable corridor shipping and navigation study area throughout the summer survey period was 7 August when 18 unique vessels were recorded. The quietest full day recorded within the Proposed Development export cable corridor itself throughout the summer survey period was also 7 August when 15 unique vessels were recorded.
For the 14 days analysed in the winter survey period, there was an average of 19 unique vessels per day recorded within the Proposed Development export cable corridor shipping and navigation study area. In terms of vessels intersecting the Proposed Development export cable corridor itself, there was an average of 18 unique vessels per day.
The daily number of unique vessels recorded within the Proposed Development export cable corridor shipping and navigation study area and the Proposed Development export cable corridor itself are presented in Figure 10.28 Open ▸ .
Figure 10.28 Unique Vessels per Day within the Proposed Development Export Cable Corridor Area and Shipping and Navigation Study Area (14 Days Winter 2021)
Throughout the winter survey period approximately 92% of unique vessel tracks recorded within the Proposed Development export cable corridor shipping and navigation study area intersected the Proposed Development export cable corridor itself.
The busiest day recorded within the Proposed Development export cable corridor shipping and navigation study area throughout the winter survey period was 19 January when 27 unique vessels were recorded. The busiest days recorded within the Proposed Development export cable corridor itself throughout the winter survey period was 24 January when 24 unique vessels were recorded.
The quietest days recorded within the Proposed Development export cable corridor shipping and navigation study area throughout the winter survey period were 14 January and 16 January when 13 unique vessels were recorded each. The quietest day recorded within the Proposed Development export cable corridor itself throughout the winter survey period was 11 January when 11 unique vessels were recorded.
10.2.2 Vessel Types
The percentage distribution of the main vessel types recorded within the Proposed Development export cable corridor shipping and navigation study area is presented in Figure 10.29 Open ▸ .
Figure 10.29 Vessel Type Distribution within Proposed Development Export Cable Corridor Area and Shipping and Navigation Study Area (28 Days Summer 2022 and Winter 2021)
Throughout the summer period, the most common vessel types in the Proposed Development export cable corridor shipping and navigation study area were fishing vessels (31%), tankers (22%), cargo vessels (16%), and recreational vessels (16%). Throughout the winter period, the most common vessel types were tankers (36%), cargo vessels (33%), and fishing vessels (20%).
Although cruise liners were recorded within the Proposed Development export cable corridor study area during the summer period, no commercial ferries were identified in the winter period, which aligns with feedback provided by Forth Ports during consultation (see 10 June 2020 entry in Table 4.1 Open ▸ ).
10.2.2.1 Tankers
The tracks of tankers recorded within the Proposed Development export cable corridor shipping and navigation study area throughout both survey periods are presented in Figure 10.30 Open ▸ .
Figure 10.30 Tanker Traffic within Proposed Development Export Cable Corridor Shipping and Navigation Study Area (28 Days Summer 2022 and Winter 2021)
Throughout the survey periods, an average of between six and seven tankers per day were recorded within the Proposed Development export cable corridor shipping and navigation study area. Regular tanker routeing included coastal transits out of the Firth of Forth.
Tanker subtypes recorded in the Proposed Development export cable corridor shipping and navigation study area included oil/chemical tankers (31%), LPG tankers (27%), and oil product tankers (22%).
10.2.2.2 Commercial Fishing Vessels
Vessel Traffic Data
The tracks of commercial fishing vessels recorded within the Proposed Development export cable corridor shipping and navigation study area throughout both survey periods, are presented in Figure 10.31 Open ▸ .
Figure 10.31 Commercial Fishing Vessel Traffic within Proposed Development Export Cable Corridor Shipping and Navigation Study Area (28 Days Summer 2022 and Winter 2021)
Throughout the survey periods an average of six commercial fishing vessels per day were recorded within the Proposed Development export cable corridor shipping and navigation study area. All the commercial fishing vessels were recorded via AIS with no recreational vessels recorded via radar. Although AIS is only mandatory for fishing vessels greater than 15 m LOA, 46% of the commercial fishing vessels recorded using AIS were under 15 m LOA.
Fishing gear type could not be identified for 52% of the commercial fishing vessels recorded. The most common fishing gear types recorded in the Proposed Development export cable corridor shipping and navigation study area during the survey periods were demersal trawlers (70%), twin trawlers (13%), and potters (11%).
The nationality of all commercial fishing vessels recorded was British.
Vessel Monitoring System Data
In addition to the vessel traffic survey data, VMS data recorded between July 2018 and June 2021 has also been analysed within the Proposed Development export cable corridor shipping and navigation study area. A density grid, using the VMS data during this period as input, is presented in Figure 10.32 Open ▸ .
Figure 10.32 VMS Fishing Density within Proposed Development Export Cable Corridor Shipping and Navigation Study Area (July 2018 – June 2021)
Similarly to the AIS data, the nearshore areas recorded the highest density of VMS fishing activity, with moderate density recorded on the eastern edge of the Proposed Development export cable corridor shipping and navigation study area.
Comparison with volume 2, chapter 12
The baseline established in volume 2, chapter 12 indicates that overall commercial fishing activity is most prominent in coastal areas, particularly in the approaches to the Firth of Forth, where the Proposed Development export cable corridor makes landfall. Activities around the Proposed Development export cable corridor are dominated by trawlers and the nationality of almost all fishing vessels observed was British.
This shows good agreement with the baseline established in this section, in terms of the fishing gear types and nationalities identified. In terms of the distribution of commercial fishing vessel activity, there is also reasonable agreement, with the majority of activity occurring in coastal areas rather than the portion of the Proposed Development export cable corridor further offshore.
10.2.2.3 Cargo Vessels
The tracks of cargo vessels recorded within the Proposed Development export cable corridor shipping and navigation study area throughout both survey periods are presented in Figure 10.33 Open ▸ .
Figure 10.33 Cargo Vessel Traffic within Proposed Development Export Cable Corridor Shipping and Navigation Study Area (28 Days Summer 2022 and Winter 2021)
Throughout the survey periods an average of five unique cargo vessels per day were recorded within the Proposed Development export cable corridor shipping and navigation study area. Regular cargo vessel routeing included coastal transits out of the Firth of Forth.
Cargo vessel subtypes recorded in the Proposed Development export cable corridor shipping and navigation study area included general cargo (64%) and container vessels (29%).
10.2.2.4 Recreational Vessels
Vessel Traffic Data
The tracks of recreational vessels recorded within the Proposed Development export cable corridor shipping and navigation study area throughout both survey periods are presented in Figure 10.34 Open ▸ .
Figure 10.34 Recreational Vessel Traffic within Proposed Development Export Cable Corridor Shipping and Navigation Study Area (28 Days Summer 2022 and Winter 2021)
An average of approximately four to five recreational vessels per day were recorded within the Proposed Development export cable corridor shipping and navigation study area during the summer survey period, with none recorded during the winter survey period. All recreational vessels were recorded via AIS, with no recreational craft recorded on radar.
RYA Coastal Atlas of Recreational Boating
Figure 10.16 Open ▸ presents a plot of the RYA Coastal Atlas heat map relative to the Proposed Development export cable corridor. Following this, Figure 10.17 Open ▸ presents a plot of features relevant to recreational boating.
The RYA Coastal Atlas shows good correlation with the AIS data, in that the majority of recreational activity is coastal.
10.2.2.5 Oil and Gas Vessels
The tracks of oil and gas vessels recorded within the Proposed Development export cable corridor shipping and navigation study area throughout both survey periods, are presented in Figure 10.35 Open ▸ .
Figure 10.35 Oil and Gas Vessel Traffic within Proposed Development Export Cable Corridor Shipping and Navigation Study Area (28 Days Summer 2022 and Winter 2021)
Throughout the survey periods, an average of approximately one oil and gas vessel per day passed within the Proposed Development export cable corridor shipping and navigation study area. The majority of these vessels were on passage north-south between Aberdeen and gas fields in the Southern North Sea.
10.2.2.6 Passenger Vessels
Vessel Traffic Data
Throughout the survey periods, an average of approximately one passenger vessel per day passed within the Proposed Development export cable corridor shipping and navigation study area during the summer survey period, with none recorded during the winter survey period. Following an assessment of Anatec’s in-house ShipRoutes database, it is concluded that this is a result of the COVID-19 pandemic which has had a substantial effect on shipping movements globally (see section 5.4.3).
Anatec ShipRoutes Database
ShipRoutes includes one notable route featuring passenger vessels that passes through the Proposed Development export cable corridor, on a similar course to the main tanker route shown in Figure 10.30 Open ▸ . This route crosses the North Sea between the Firth of Forth and Hamburg[7] and constitutes approximately 110 transits per year (one vessel every three to four days).
This correlates with feedback received from Forth Ports during consultation indicating that under normal circumstances, when the effects of the COVID-19 pandemic are not present, there are around 125 visits per year by cruise ships to the Forth. It should be noted that the Proposed Development export cable corridor only covers one approach to the Forth and cruise schedules and numbers are subject to fluctuation season on season.
10.2.3 Vessel Sizes
10.2.3.1 Vessel Length
A plot of all vessel tracks (excluding temporary traffic) recorded within the Proposed Development export cable corridor shipping and navigation study area throughout the survey periods, colour-coded by LOA, is presented in Figure 10.36 Open ▸ . Following this, the distribution of these LOA classes by survey period is presented in Figure 10.37 Open ▸ .
Figure 10.36 Vessel Traffic Movements within Proposed Development Export Cable Corridor Shipping and Navigation Study Area by Vessel LOA (28 Days Summer 2022 and Winter 2021)
Figure 10.37 Vessel LOA Distribution within Proposed Development Export Cable Corridor and Shipping and Navigation Study Area (28 Days Summer 2022 and Winter 2021)
Vessel LOA was available for approximately 89% of vessels recorded in the Proposed Development export cable corridor shipping and navigation study area throughout both survey periods and ranged from 5 m for a RNLI lifeboat to 330 m for two crude oil tankers.
Excluding the vessels for which an LOA was not available, the average LOA of all vessels within the Proposed Development export cable corridor shipping and navigation study area throughout the summer and winter survey periods was 69 m and 98 m, respectively.
10.2.3.2 Vessel Draught
A plot of all vessel tracks (excluding temporary traffic) recorded within Proposed Development export cable corridor shipping and navigation study area throughout the survey periods, colour-coded by draught, is presented in Figure 10.38 Open ▸ . Following this, the distribution of these draught classes by survey period is presented in Figure 10.39 Open ▸ .
Figure 10.38 Vessel Traffic Movements within Proposed Development Export Cable Corridor Shipping and Navigation Study Area by Vessel Draught (28 Days Summer 2022 and Winter 2021)
Figure 10.39 Vessel Draught Distribution within Berwick Bank Export Cable Corridor and Shipping and Navigation Study Area (28 Days Summer 2022 and Winter 2021)
Vessel draught was available for approximately 50% of vessels recorded in the Proposed Development export cable corridor shipping and navigation study area throughout both survey periods and ranged from 0.9 m for a fishing vessel to 20 m for a crude oil tanker.
Excluding the vessels for which a draught was not available, the average draught of all vessels within the Proposed Development export cable corridor shipping and navigation study area throughout the summer and winter survey periods was 4.6 m and 5.3 m respectively.
10.2.4 Anchoring Activity
The same criteria outlined in section 10.1.4 for identifying anchored vessels bas been applied to the vessel traffic data for the Proposed Development export cable corridor shipping and navigation study area.
After applying these criteria, no vessels were deemed to be at anchor within the Proposed Development export cable corridor shipping and navigation study area.
11 Base Case Vessel Routeing
11.1 Definition of a Main Commercial Route
Main commercial routes have been identified using the principles set out in MGN 654 (MCA, 2021). Vessel traffic data are assessed and vessels transiting at similar headings and locations are identified as a main route. To help identify main routes, vessel traffic data can also be interrogated to show vessels (by name and/or operator) that frequently transit those routes. The route width is then calculated using the 90th percentile rule from the median line of the potential shipping route as shown in Figure 11.1 Open ▸ . Additionally, the outputs of consultation undertaken with local stakeholders assisted in the identification of the main commercial routes.
Figure 11.1 Illustration of Main Route Calculation (MCA, 2021)
11.2 Pre Wind Farm Main Commercial Routes
A total of 15 main commercial routes were identified within the Proposed Development array area shipping and navigation study area from the vessel traffic survey data[8] and consultation. These main commercial routes and corresponding 90th percentiles within the Proposed Development array area shipping and navigation study area are shown relative to the Proposed Development array area in Figure 11.2 Open ▸ . Following this, a description of each route is provided in Table 11.1 Open ▸ , including the average number of vessels per day, start and end locations and main vessel types. It is noted that the start and end locations are based on the most common destinations transmitted via AIS by vessels on those routes.
To ensure all main commercial routes are captured, the long-term vessel traffic data has been used to validate the main commercial routes identified from the vessel traffic survey data, with consideration given to the change in vessel traffic movements due to the presence of Seagreen.
Figure 11.2 Main Commercial Routes and 90th Percentiles within Proposed Development Array Area Shipping and Navigation Study Area (Pre Wind Farm)
Table 11.1 Description of Main Commercial Routes
There is likely additional routeing in and out of the Firth of Forth which falls outside of the Proposed Development array area shipping and navigation study area. This includes tankers headed for Braefoot Bay which may be located further inshore, as noted by Forth Ports during consultation (see 12 June 2020 entry in Table 4.1 Open ▸ ) and passenger vessels (as noted in section 10.1.2.6). Given the distance from the Proposed Development array area, it is not anticipated that such routeing will be affected by the presence of the Proposed Development in isolation. However, such routeing is considered in the assessment of cumulative deviations where appropriate (see section 15.6.2).
12 Adverse Weather Vessel Traffic Movements
Some vessels and vessel operators may operate alternative routes during periods of adverse weather. This section focuses on vessel movements in adverse weather. Consideration is given to the implications of the presence of, or activities associated with, the Proposed Development during adverse weather. For example, if a commercial vessel is unable to make passage, or a small craft is unable to access safe havens.
Adverse weather includes wind, wave and tidal conditions as well as reduced visibility due to fog. Adverse weather can hinder a vessel’s standard route, its speed of navigation and/or its ability to enter the destination port. Adverse weather routes are assessed to be significant course adjustments to mitigate vessel motion in adverse weather conditions. When transiting in adverse weather conditions, a vessel is likely to encounter various types of weather and tidal phenomena, which may lead to severe roll motions, potentially causing damage to cargo, equipment and/or discomfort and danger to persons on board. The sensitivity of a vessel to these phenomena will depend on the actual stability parameters, hull geometry, vessel type, vessel size and speed.
12.1 Identification of Periods with Adverse Weather
Historical weather information provided by the Met Office (Met Office, 2019) has been used to identify periods of adverse weather during 2019 (the year covered by the long-term vessel traffic data) when routes within or in proximity to the Proposed Development could be considered most likely to be altered or cancelled. The key weather events identified are detailed in Table 12.1 Open ▸ .
Table 12.1 Key Weather Events During 2019 Relevant to the Proposed Development (Met Office)
12.2 Commercial Routeing Changes
The long-term vessel traffic data has been used to identify potential commercial routeing activity related to adverse weather conditions within and in proximity to the Proposed Development, with the periods outlined in Table 12.1 Open ▸ studied most closely.
No substantial alternative routeing was observed. However, during consultation adverse weather routeing was raised by the MCA as a topic that requires attention (see 9 March 2021 entry in Table 4.1 Open ▸ ). This was reflected in feedback received during the second Hazard Workshop, including from Forth Ports indicating that the region is known to experience significant bad weather. The FMA highlighted the Marr Bank as a particular hazard of note for larger tankers navigating coastally in adverse weather (see 27 July 2022 entries in Table 4.1 Open ▸ ).
Given the coastal nature of vessel routeing in the region, it is highly likely that many vessels choose to navigate a course that minimises exposure to any adverse weather, whilst also accounting for other factors, such as journey time. Route 1 in Figure 11.2 Open ▸ is such an example of a route where the optimal passage for minimising journey time has been conceded in favour of a passage which keeps a closer distance to the UK east coast where there is greater shelter from adverse weather. This also aligns with feedback from Intrada Ship Management during consultation (see 15 December 2021 entry in Table 4.1 Open ▸ ).
Therefore, the potential for adverse weather hazards due to deviations of main commercial routes has been considered when determining deviations for both the Proposed Development in isolation (see section 15.5) and cumulative scenarios (see section 15.6).
In consultation feedback Intrada Ship Management noted that given their vessels carry deck cargoes they are particularly sensitive to rolling and pitching and will need adequate sea room in order to select headings that mitigate the risks associated with weather/tidal direction.
12.3 Small Craft Use of Safe Havens
As indicated by the long-term vessel traffic data, RYA Coastal Atlas of Recreational Boating (RYA, 2019) and consultation feedback, recreational vessel activity predominantly occurs inshore of the Proposed Development array area (and the other offshore wind farm developments in the region) and therefore it is not anticipated that the presence of the Proposed Development array area or associated activities will have a substantial effect on the ability of small craft to access safe havens in adverse weather conditions.
For the less frequent cases of recreational vessels navigating further offshore, the Scottish Whitefish Producers Association indicated that the overall minimum spacing between structures proposed (1,000 m) may not be sufficient for safe navigation. However, this minimum spacing is greater than that present at most existing offshore wind farm developments in the UK, some of which have much greater volumes of small craft activity associated with them (e.g. Rampion Offshore Wind Farm in the English Channel). Figure 12.1 Open ▸ presents an indicative small craft of length 15 m navigating internally within an offshore wind farm array with 1,000 m spacing between structures.
Figure 12.1 Indicative Small Craft Navigating within Wind Farm Array
There is substantial sea room available for a small craft to navigate safely, including in the majority of adverse weather conditions. As per International Convention on the Safety of Life at Sea (SOLAS) Chapter V (IMO, 1974), all vessels at sea are required to passage plan and part of the passage planning process requires them to consider weather forecasts and subsequent conditions. It is anticipated that vessels would then take account of these forecasts prior to embarking on a passage through or offshore of the array.
Taking into account the need for consultation on the final array layout post consent and the requirements of SOLAS Chapter V, there are not considered to be any significant effect on access to safe havens due to the presence of the Proposed Development or associated activities.
13.1 Very High Frequency Communications (Including Digital Selective Calling)
In 2004, trials were undertaken at the North Hoyle Offshore Wind Farm, located off the coast of North Wales. As part of these trials, tests were undertaken to evaluate the operational use of typical small-vessel VHF transceivers (including Digital Selective Calling (DSC)) when operated close to wind turbines.
The wind turbines had no noticeable effect on voice communications within the array or ashore. It was noted that if small craft vessel to vessel and vessel to shore communications were not significantly affected by the presence of wind turbines, then it is reasonable to assume that larger vessels with higher powered, and more efficient, systems would also be unaffected.
During this trial, a number of telephone calls were made from ashore, within the array, and on its offshore side. No effects were recorded using any system provider (MCA and QinetiQ, 2004).
Furthermore, as part of SAR trials carried out at the North Hoyle Offshore Wind Farm in 2005, radio checks were undertaken between the Sea King helicopter, and both Holyhead and Liverpool coastguards. The aircraft was positioned to the offshore side of the array, and communications were reported as very clear with no apparent degradation of performance. Communications with the service vessel located within the array were also fully satisfactory throughout the trial (MCA, 2005).
In addition to the North Hoyle trials, a desk-based study was undertaken for the Horns Rev 3 Offshore Wind Farm in Denmark in 2014, and it was concluded that there were not expected to be any conflicts between point to point radio communications networks, and no interference upon VHF communications (Energinet, 2014).
Following consideration of these reports, and noting that since the trials above there have been no significant issues with regards to VHF observed or reported, the presence of the Proposed Development is anticipated to have no significant risk upon VHF communications.