Publication - Progress report

Draft Sectoral Marine Plans for Offshore Renewable Energy in Scottish Waters: Socio - Economic Assesment

Published: 25 Jul 2013
Part of:
Marine and fisheries
ISBN:
9781782567509

The study reported here provides a high level socio-economic appraisal of the potential costs and benefits to activities that may arise as a result of offshore wind, wave or tidal development within the Draft Plan Options as part of possible future Scotti

383 page PDF

4.7 MB

383 page PDF

4.7 MB

Contents
Draft Sectoral Marine Plans for Offshore Renewable Energy in Scottish Waters: Socio - Economic Assesment
C5. Commercial Shipping

383 page PDF

4.7 MB

C5. Commercial Shipping

C5.1 Scoping Results

The results of the scoping assessment are presented in Table C5.1 (Offshore Wind), Table C5.2 (Wave) and Table C5.3 (Tidal) and indicate whether more detailed assessment is required (Y/N).

Table C5.1 Offshore Wind

North North-East South-West West North-West
OWN1 OWN2 OWNE1 OWNE2 OWSW1 OWSW2 OWW1 OWW2 OWW3 OWNW1
Spatial overlap between Draft Plan Option areas and commercial navigation routes greater than 5 or more vessels per day or ferry route Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only N Y* - for central and high scenarios only
IMO recognised "ship routeing system" N N N N N N N N Y N
Potential impact on ferry turnaround times N Y* - for central and high scenarios only N Y* - for central and high scenarios only N N N N N N
Spatial overlap between Draft Plan Option areas and commercial anchorages N N N N N N N N N N
Spatial overlap between cable routes and commercial anchorages N Y - qualitative assessment N N Y - qualitative assessment N

* Draft Plan Option areas transected by commercial navigation route(s) or ferry route greater than 5 or more vessels per day. However, arrays for low scenario occupy less than 5% of Draft Plan Option areas and it has been assumed that spatial planning of the Draft Plan Option areas can be used to avoid significant impacts under this scenario.

Table C5.2 Wave

North West North-West
WN1 WN2 WN3 WW1 WW2 WW3 WNW1 WW4
Spatial overlap between Draft Plan Option areas and commercial navigation routes greater than 5 or more vessels per day or ferry route N* N* N* N* N* N N N
IMO recognised "ship routeing system" N N N N N N Y N
Potential impact on ferry turnaround times N N N* N N N N N
Spatial overlap between Draft Plan Option areas and commercial anchorages N N N N N N N N
Spatial overlap between cable routes and commercial anchorages N Y - qualitative assessment N N

* Draft Plan Option areas transected by commercial navigation route(s) or ferry route greater than 5 or more vessels per day. However, arrays for all scenarios occupy less than 1% of Draft Plan Option areas and it has been assumed that spatial planning of the Draft Plan Option areas can be used to avoid significant impacts under these scenarios.

Table C5.3 Tidal

North South-West West
TN1 TN2 TN3 TN4 TN5 TN6 TN7 TSW1 TW1 TW2
Spatial overlap between Draft Plan Option areas and commercial navigation routes greater than 5 or more vessels per day or ferry route Y* - for high scenario only Y* - for high scenario only N Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only
IMO recognised "ship routeing system" N N N N N N N N N Y
TN1 TN2 TN3 TN4 TN5 TN6 TN7 TSW1 TW1 TW2
Potential impact on ferry turnaround times Y* - for high scenario only Y* - for high scenario only N Y* - for high scenario only N Y* - for high scenario only Y* - for high scenario only N N Y* - for high scenario only
Spatial overlap between Draft Plan Option areas and commercial anchorages N N N N N N N N N N
Spatial overlap between cable routes and commercial anchorages N N Y - qualitative assessment

* Draft Plan Option areas transected by commercial navigation route(s) or ferry route greater than 5 or more vessels per day. However, arrays for low and central scenarios occupy less than 5% of Draft Plan Option areas and it has been assumed that spatial planning of the Draft Plan Option areas can be used to avoid significant impacts under these scenarios.

C5.2 Assessment Results - Estimation of Costs and Benefits

C5.2.1 Quantitative Assessment of Impacts to Shipping Routes and Ferry Routes

Indicative costs associated with modifying existing navigation routes for ferries and commercial shipping have been calculated with respect to additional steaming time.

C5.2.1.1 IMO ship routing lanes

It is noted that two Draft Plan Option areas overlap IMO ship routing lanes within the North-West region, these are wave site WNW1 and the wind site OWW3 (see Figure B5). The wind development ( OWW3) marginally intersects the ship routing lane, whereas the lane transects the entire length of the wave development ( WNW1). These measures are international standards; for the purposes of this assessment no deviation costs are estimated and it is considered that renewable developments within these Draft Plan Option areas would be placed away from IMO ship routing lanes.

C5.2.1.2 Commercial shipping and ferry routes - wind

Calculated costs associated with transiting around wind development boundaries for commercial shipping and ferry routes are summarised set out in Table 5. With the exception of OWW3, all wind Draft Plan Option areas are scoped in for the central and high development density scenarios only. As the Draft Plan Option areas are located along commercial shipping navigation routes with over five vessels a day, and would have over 5% of the Draft Plan Option area developed under the central and high scenarios.

Renewable development scenarios were applied using the methodology outlined in Appendix B5, in order to derive associated costs. The worst credible scenario has been evaluated to provide a conservative economic cost which considers that routes running perpendicularly offshore from the coast would mostly be impacted by the location of the wind developments. The largest deviation and associated cost are observed with the higher development scenarios, which are often up to double the cost associated with the central scenario as demonstrated in Table C5.4.

Table C5.4 Offshore Wind

North North-East South-West West North-West
OWN1 OWN2 OWNE1 OWNE2 OWSW1 OWSW2 OWW1 OWW2 OWNW1
Scoping output: Spatial overlap between Draft Plan Option areas and commercial navigation routes greater than 5 or more vessels per day or ferry route Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only Y* - for central and high scenarios only
Central Scenario Deviation (nm) 2.2 1.7 1.5 1.4 0.2 0.2 1.1 0.8 2.0
Cost individual journey (£) 229 178 156 143 25 18 113 83 208
Annual average journeys 1,485 1,762 23,159 6,022 2,914 21,392 1,664 1,960 642
Cost annual journey (£ millions) 0.3404 0.3136 3.6022 0.8609 0.0726 0.3941 0.1874 0.1621 0.1335
High Scenario Deviation (nm) 4.4 3.4 3.0 2.8 0.5 0.2 2.2 1.7 4.0
Cost individual journey (£) 455 358 316 291 53 18 232 172 415
Annual average journeys 1,485 1,762 23,159 6,022 2,914 21,392 1,664 1,960 642
Cost annual journey (£ millions) 0.6751 0.6315 7.3078 1.7539 0.1551 0.3941 0.3861 0.3377 0.2665

C5.2.1.3 Commercial shipping routes - wave

All wave developments are scoped out for assessments as the density of the development within each Draft Plan Option area is less than 1%.

C5.2.1.4 Commercial shipping and ferry routes - tide

All tide developments are scoped in for the high development scenarios with the exception of TN3, this site is not scoped in under the high scenario due to its relatively low sea area use for commercial shipping. The scoped in tidal Draft Plan Option areas are located close to, and adjoining the coast, and overlap with commercial shipping and ferry routes. Of note are the series of developments in the Northern sector, between the Scottish mainland and The Orkney Islands, with a series of other developments within the Orkney Islands and within the Shetland Islands. As the Draft Plan Option areas are located between the islands, in a high development scenario, the sea area usage is a higher percentage, and therefore provides cumulatively significant deviations for shipping. In all cases depths are not sufficient to scope out the Draft Plan Option areas, as depths are predominantly less than 75m with only small regions having larger depths. Off the west and south west coast of Scotland and in relation to developments TW1, TW2 and TSW1, the navigation routes perpendicularly offshore from the coast would mostly be impacted by the location of the tide Draft Plan Option areas, while vessels moving in a north to south direction are less likely to be obstructed.

Calculated costs associated with transiting around tidal development boundaries (where depths are not great enough to safely navigate over them) are summarised in Table C5.5.

Table C5.5 Tide

North South-West West
TN1 TN2 TN4 TN5 TN6 TN7 TSW1 TW1 TW2
Scoping output: Spatial overlap between Draft Plan Option areas and commercial navigation routes greater than 5 or more vessels per day or ferry route Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only Y* - for high scenario only
High Scenario Deviation (nm) 0.29 0.05 0.22 0.04 0.03 0.04 0.25 0.27 0.09
Cost individual journey (£) 30 6 22 4 3 4 26 28 10
Annual average journeys 13,654 5,315 2,365 1,764 54,467 41,382 3,781 3,608 7,711
Cost annual journey (£ millions) 0.4163 0.0299 0.0530 0.0075 0.1885 0.1621 0.0983 0.1005 0.0735

C5.2.1.5 Ferry routes - wind

Based on the implemented development scenarios, a number of ferry routes intersect with wind developments. Using the Scottish Government supplied Passenger and Vehicle ferry routes GIS layer ferry routes affected by wind developments include those listed in Table C5.6. The assessment of fuel used for additional steaming distance is part of the overall shipping and ferry deviation calculations detailed in Table C5.4.

Table C5.6 Wind

Draft Plan Option Area Ferry Route Location of Intersection
OWN2 Lerwick - Hanstholm Through the middle
OWN2 Aberdeen - Lerwick Intersects with South West corner
OWNE2 Aberdeen - Kirkwall Crosses Western corner
OWNE2 Aberdeen - Lerwick Crosses Easter corner

C5.2.1.6 Ferry routes - wave

All wave developments are scoped out for assessments as the density of the development within each Draft Plan Option area is less than 1%. Therefore there are no impacted ferry routes.

C5.2.1.7 Ferry routes - tide

Based on the implemented development scenarios, there 10 ferry routes intersecting the tide Draft Plan Option areas as shown in Table C5.7. It is considered that spatial planning will seek to locate tidal developments to minimise interactions, which is especially important where ferry services provide lifeline connections to island communities. The overall calculation of fuel costs based on deviation around tidal sites has been presented in Table C5.5 for all shipping, including ferry services. It should be noted that site specific assessments on individual developments would address ferry route geographic extents, at which time consultation with Harbour Authorities and ferry operators would highlight potential intersections and route deviation.

Table C5.7 Tide

Draft Plan Option Area Ferry Route Location of intersection
TN1 Orkney ferries (Other ferry routes) Through the middle
TN1 Orkney ferries (Other ferry routes) Through the middle
TN1 Orkney ferries (Other ferry routes) Through the middle
TN2 Orkney ferries (Other ferry routes) Through the middle
TN2 Kirkwall - Lerwick Crosses southern end
TN2 Kirkwall - Stronsay Crosses southern end
TN2 Orkney ferries (Other ferry routes) Crosses southern end
TN4 Kirkwall - Lerwick Crosses South East corner
TN6 Toft - Yell (Ulsta) Through the middle
TW2 Campbeltown - Ballycastle Crosses Southern end

C5.2.2 Qualitative Assessment of Increase in Marine Risk

Potential risks to commercial shipping activities from offshore wind developments include:

  • Collisions with structures and (or) other vessels either under power or drifting;
  • Effects of the wind turbine generators, blades and supports on navigation safety aids, including position-fixing systems ( AIS, radar and GPS positioning) and communications ( VHF radio); and
  • Issues of visibility including obscuration of visual markers as well as obscuration to vessel or shore-based radar when in proximity to the developments.

Due to the commercial navigation intensity combined with other water users such as fishing and recreational users, the potential for vessel to vessel encounters exists. This does not however translate to vessel to vessel collision risk or vessel to structure collision. Instead, the collision risk and frequency would depend on a wide range of factors including conditions, visibility, vessel characteristics and vessel speed. In respect of a wind farm site, the outer structures are most exposed to shipping collision and relate to vessels navigating in restricted visibility, or those with inadequate bridge watch keeping, or vessels adrift and/or not under command. In terms of vessel to vessel collisions, wind farm developments may be a contributory factor if radar systems are affected by reflection from blades and towers.

In the case of the wind Draft Plan Option areas in this study, these are sited further offshore but notably overlap or are positioned in close proximity to established recreational and commercial shipping navigation routes. The implementation of developments on or in close proximity to these routes could lead to the diversion of vessel traffic thereby creating much busier navigation routes and increasing the potential for vessel encounters. In terms of navigation safety and visibility aids, studies by the MCA in association with QinetiQ found that the effects of offshore wind structures on communication and position-fixing systems were not significant enough to affect navigational efficiency or safety ( MCA & QinetiQ, 2004). The exception however was a recognised risk to ship-borne and shore-based radar systems. As the presence of wind farm structures can produce false (multiple and reflected) radar echoes, due to the vertical extent of the wind turbine generators. At the same time the turbines can introduce interference and cause shadowing round the structures or development. The potential for radar induced collision is greater with commercial vessel and smaller craft interaction, as smaller craft provide a limited radar return potential, which could potential be 'lost' if wind farm radar effects are significant. The concern is that due to the interference on radar systems from wind farm developments, commercial vessels will reduce the gain of their radar sets and as a result loose smaller recreational craft.

This risk can be mitigated by carrying AIS which provides another means of verifying radar targets. However, AIS carriage is optional for some classes of vessels, including smaller commercial, recreational and fishing vessels. As a result of the recognised risk, documents have been produced which give guidance to mariners navigating in the vicinity of wind farms ( MCA, 2004; 2008a), as well as templates for wind farm siting in relation to navigation routes ( MCA, 2008b) and the assessment of impacts ( DTI, 2005).

With regards to wave developments, the presence of floating structures on or near the sea surface poses a risk to all vessels. This is primarily through the risk of an underwater collision or snagging of vessel lines with structures and their moving parts, while the vessel is either underway or anchoring. Any wave development with surface or near surface wave devices would be identified on a chart and appropriately marked with buoyage as an exclusion zone. The effectiveness of these controls relies on both commercial and recreational vessels monitoring up to date charting information and maintaining an effective watch whilst at sea. The assessment of vessel to structure, and vessel to vessel collision risks described for the wind developments are also applicable here. The largest risks are from the devices located on the outer extents of the development.

The risk associated with communications and visibility through position-fixing systems is not applicable in this instance as the wave devices are at the water surface and do not extend vertically to cause interference. There is however the additional risk of the wave devices breaking free of their moorings and floating into nearby navigation routes, thereby creating a risk of collision. The risk of a vessel not under command, or a vessel struggling to maintain its course and speed in heavy weather and drifting into the wave development exclusion zone should also be recognised. In this instance the ship's crew and the emergency services and their personal would be at risk in performing their duties to preserving life at sea.

The risk associated with the tidal developments is the presence of submerged structures on the seabed posing a risk to surface navigating vessels. This is primarily through the risk of a collision or snagging of vessel lines with structures and their moving parts, while the vessel is either underway or anchoring. Tidal sites would be marked on charts with clearance distances identified. The effectiveness of these controls relies on both commercial and recreational vessels monitoring up to date charting information.

For all the renewable developments, there is the increased risk of collision with installation vessels along cable routes while cabling is laid. This risk is increased in proximity to navigation channels (for example, in port and harbour approaches) and through increased vessel activity in these areas. The risk is transient in nature, and can be mitigated for through planning and informing relevant parties through notices to mariners. Although less likely, but still apparent, is the additional risk of the physical snagging of anchors on cables prior to burial. If cables are laid on the seabed the risk would continue during the operational period of the developments. Burying the cables below the seabed or protection to an appropriate depth, would limited the exposure at the seabed surface and the potential risk. The cabling route would be marked on charts and thereby reduced the risk of damage from anchoring vessels, assuming that vessels update their charted information. Any cabling across port approach channels where routine maintenance dredging is carried out would require agreed burial depth and possible armour protection to prevent damage to dredger dragheads and cabling.

C5.2.3 Quantitative Assessment of Impacts to Displacement of Formal and Informal Anchorages

There are no overlaps between any commercial anchorages and the renewable Draft Plan Option areas or the implemented development scenarios.

There is the potential for overlap between the proposed cable routes and commercial anchorages for wind, wave and tide Draft Plan Option areas. Cable routes associated with OWW1, OWW2 (wind Draft Plan Option areas), WW1, WW2, WW3 (wave Draft Plan Option areas) and TW1 and TW2 (tide Draft Plan Option areas). This would be subject to a site specific risk assessment for each cable route, during which the developer would take into account ship anchoring requirements and history, and identify alternative suitable anchorage locations. Any newly identified anchorage locations are required to provide some protection from weather, wind and waves, be of sufficient seabed depth and sediment to hold an anchor and have enough room for a vessel at anchor to swing with varying conditions.

At the time of writing information on informal anchorages is not available. Therefore in the event that Draft Plan Option areas or associated cable routes overlap these anchorages, similar alternatives in terms of orientation and shielding from wave and storm conditions would be required. The same risks associated with commercial anchorages also apply to informal sites.

C5.2.4 Benefits

Construction of the renewable developments would lead to an increase of commercial short transits in relation to the preparation and construction of the developments. This would in turn generate some economic return for the ports and harbours used in relation to the construction.

C5.2.5 Summary

The assessment has concluded that the most significant deviation for shipping occurs with wind farm development sites, specifically in the North-East around OWNE1 (£7.3 million annually) and to a lesser extent around OWNE2 (£1.8 million annually). The cost relates to additional fuel usage for steaming times as a summation. Within the North at OWN1 and OWN2, circa £0.65 million of additional fuel use has been assessed. At OWN2 this relates to vessel traffic transiting north-south along the eastern side of the Shetland Islands in-combination with vessels transiting to Lerwick and other smaller Shetland Islands Council ports.

All wave sites are scoped out as spatial planning can be used to avoid undue effect on commercial shipping. All tide developments are scoped in for the high development scenarios with the exception of TN3, this site is not scoped in under the high scenario due to its relatively low sea area use for commercial shipping. All tidal sites provide an annual deviation cost of fuel less than £0.2million, with the exception of the West TN1 site which provides a £0.4 million cost.

In respect of ferry routes, a number of routes transect Draft Plan Option areas. The assessment of additional fuel usage is included within the Shipping assessment. Route transecting Draft Plan Option areas have been identified in Tables C5.6 and C5.7.

For all the renewable developments, there is the increased risk of collision with installation vessels along cable routes while cabling is laid. This risk is increased in proximity to navigation channels (for example, in port and harbour approaches) and through increased vessel activity in these areas. The risk is transient in nature, and can be mitigated for through planning and informing relevant parties through notices to mariners.

C5.3 References

Baxter, J.M., Boyd, I.L., Cox, M., Donald, A.E., Malcolm, S.J., Miles, H., Miller, B., Moffat, C.F., (Editors), 2011. Scotland's Marine Atlas: Information for the national marine plan. Marine Scotland, Edinburgh.

Department of Trade and Industry, 2005. Guidance on the Assessment of the Impact of Offshore Wind Farms: Methodology for Assessing the Marine Navigational Safety Risks of Offshore Wind Farms. DTI/Pub 8145/0.5k/12/05/NP

Maritime and Coastguard Agency, 2004. Proposed Offshore Renewable Energy Installations ( OREI), Guidance on Navigational Safety Issues. Marine Guidance Note 275

Maritime and Coastguard Agency, 2008a. Offshore Renewable Energy Installations ( OREIs), Guidance on UK Navigational Practice, Safety and Emergency Response Issues. Marine Guidance Note 371.

Maritime and Coastguard Agency, 2008b. Offshore Renewable Energy Installations ( OREIs), Guidance to Mariners Operating in the Vicinity of UK OREIs. Marine Guidance Note 372.

NOREL NAV Sub Group, 2012. Draft Copy: 'Under Keel Clearance - Policy Paper Guidance To Developers in Assessing Minimum Water Depth Over Devices'. December 2012

Transport Scotland. 2012. Scottish Ferry Services: Ferries Plan (2013-2022). 89pp. http://www.transportscotland.gov.uk/files/documents/reports/j254579_1.pdf


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