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RECORD OF THE APPROPRIATE ASSESSMENT UNDERTAKEN FOR APPLICATIONS UNDER
SECTION 36 OF THE ELECTRICITY ACT 1989
Projects:
DOCKING SHOAL OFFSHORE WIND FARM (AS AMENDED)
RACE BANK OFFSHORE WIND FARM (AS AMENDED)
DUDGEON OFFSHORE WIND FARM
December 2011, updated June 20121
1 INTRODUCTION
1.1 This is a record of the Appropriate Assessment undertaken by the Secretary of State for the
Department of Energy and Climate Change (DECC) in respect of each of the three projects2
listed above.
1.2 Each project is not directly connected with, or necessary to, the management of a European
site3. However, each project may affect European sites. The purpose of this Appropriate
Assessment is to determine whether or not each project will adversely affect the integrity of the
European sites recorded in Table 1.1, in view of their Conservation Objectives.
Table 1.1 European sites which may be affected by each project
Project
European Site
North Norfolk Coast Special
Protection Area (SPA)
The Wash and North Norfolk Coast Special Area of Conservation
(SAC)
Inner Dowsing, Race Bank and North Ridge candidate
Special Area of
Conservation (cSAC) 4
Docking Shoal
Race Bank
Dudgeon
1.3 By virtue of the distance of each project from the shore, the Appropriate Assessment is required
by either:
Regulation 61 of The Conservation of Habitats and Species Regulations 2010 (as
amended), for projects within 12 nautical miles (Docking Shoal); or
Regulation 25 of the Offshore Marine Conservation (Natural Habitats, &c.) Regulations
2007 (as amended), for projects beyond 12 nautical miles (Race Bank and Dudgeon).
1 Text amended, 16 July 2012, to remove details of turbine manufacturer
2 The projects are defined as the construction and operation of:
a)
Docking Shoal Offshore wind farm, as proposed in the application of December 2008 and amended in July 2011 to seek consent for a 540MW wind
farm but build the initial phase to 100MW only;
b)
Race Bank Offshore wind farm as proposed in the application of January 2009 and amended in July 2011; and
c)
Dudgeon Offshore wind farm, as proposed in the application of June 2009.
3 European site as defined in Regulation 24 of the Offshore Marine Conservation (Natural Habitats, &c.) Regulations 2007 and Regulation 8 of The
Conservation of Habitats and Species Regulations 2010 (as amended).
4 The Inner Dowsing, Race Bank and North Ridge candidate Special Area of Conservation has been submitted by the UK Government to the European
Commission, but not yet formally designated. As a matter of policy for planning and all other consent regimes, the UK Government treat candidate SACs as
if they were fully designated.
2
This Appropriate Assessment is in accordance with Council Directive 92/43/EEC on the
conservation of natural habitats under wild fauna and flora (“the Habitats Directive”) and
Council Directive 2009/147/EC on the conservation of wild birds (“the Birds Directive”).
1.4 This record should be read in conjunction with the following documentation and
correspondence, which provides extensive background information:
Information for Race Bank Offshore Wind Farm Shadow Appropriate Assessment.
ABPmer, August 2011;
Collision Risk Modelling of Sandwich tern Sterna sandvicensis in relation to Race
Bank and Docking Shoal Offshore Wind Farms. ECON, July 2011;
Dudgeon Offshore Wind Farm: Updated Collision Risk Modelling of Sandwich tern
Stern sandvicensis, July 2011;
Outstanding issues relating to Docking Shoal, Race Bank and Dudgeon Offshore
Wind Farms. Joint Nature Conservation Committee (JNCC) and Natural England, 29th
July 2011;
Sandwich tern population model and avoidance rates. JNCC and Natural England,
June 2011;
Population Viability Analysis (PVA) of the North Norfolk Sandwich tern Sterna
sandvicensis Population (Final Report), Mackenzie et al. April 2011;
Dudgeon Offshore Wind Farm. Supplementary Ornithological Information, February
2010;
Docking Shoal and Race Bank Offshore Wind Farm. Supplementary Environmental
Information, September 2009;
Dudgeon Offshore Wind Farm. Environmental Statement, June 2009;
Race Bank Offshore Wind Farm. Environmental Statement, January 2009; and
Docking Shoal Offshore Wind Farm. Environmental Statement, December 2008.
So far as is possible, the information in these documents is summarised here, but not
duplicated.
1.5 The Marine Management Organisation (MMO) has provided feedback on previous versions of
this assessment (MMO, 2012a) and is separately undertaking an Appropriate Assessment of
the Marine Licence applications for these projects (MMO, 2012b).
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2 PROJECT LOCATIONS
2.1 All three projects lie in the south of the Greater Wash Strategic Environmental Assessment
Area (Figure 2.1).
a) Docking Shoal lies approximately 14km from the north Norfolk coast;
b) Race Bank lies approximately 27km from the north Norfolk coast; and
c) Dudgeon lies approximately 32km from the north Norfolk coast.
Figure 2.1 Project locations
(Source: The Crown Estate)
2.2 Docking Shoal: Export cables pass through The Wash and North Norfolk Coast SAC to make
landfall east of the mouth of the River Nene (Figure 2.2).
2.3 Race Bank: Overlaps the Inner Dowsing, Race Bank and North Ridge cSAC. The export
cables from Race Bank pass through The Wash and North Norfolk Coast SAC to make landfall
east of the mouth of the River Nene (Figure 2.2).
2.4 Dudgeon: There are no European sites either within Dudgeon Offshore Wind Farm or the
export cable corridor (Figure 2.2).
4
Figure 2.2 European sites in the vicinity of the projects
(Source: Royal Haskoning 2011)
5
3 PROJECT DESCRIPTIONS
3.1 This Appropriate Assessment considers the application for the construction and operation of
three offshore wind farms in the vicinity of The Wash off the coast of Norfolk and Lincolnshire.
3.2 The Docking Shoal offshore wind farm application, for a site with a maximum generating
capacity of 540 MW, was submitted by Centrica (DSW) Limited to the Secretary of State in
December 2008. Subsequent modifications submitted in July 2011 sought consent for an initial
phase construction of up to 100 MW. The full 540 MW site comprises up to 108 turbines, in an
area of around 75 Km2, with 3 offshore sub-stations and inter-array cabling linking the turbines
and the offshore sub-stations.
3.3 The Race Bank offshore wind farm application, for a site with a maximum generating capacity
of 620 MW, was submitted by Centrica (RBW) Limited in January 2009. Subsequent
modifications submitted in July 2011- described below – reduced the maximum capacity to 580
MW for a development comprising up to 116 turbines in an area of up to 65 Km2, 3 offshore
sub-stations and inter-array cabling linking the turbines and offshore sub-stations.
3.4 The Dudgeon offshore wind farm application, for a site with a maximum generating capacity of
560 MW, was submitted by Warwick Energy Limited in June 2009. The proposed development
comprises up to 168 turbines in an area of around 35 Km2, 3 offshore sub-stations, 4
meteorological masts, inter-array cabling, and an accommodation platform.
3.5 The project locations and indicative export cable routes are described in Section 2. An
indicative construction programme is shown in Table 3.1.
3.6 Sandwich terns (Sterna sandvicensis) are considered a sensitive receptor due to the potential
for cumulative bird strike at the offshore wind farms in The Wash. In order to proceed,
restrictions may be imposed on turbine numbers, locations and sizes until further evidence
emerges on how Sandwich terns interact with offshore wind farms in The Wash. The Docking
Shoal and Race Bank projects have been modified by the Developer, within the Rochdale
Envelope5, principally to reduce predicted impacts on Sandwich terns. The key modifications
are described below.
Exclusion of ‘Tern Sensitive Areas’ – Race Bank
3.7 The application for Race Bank has been amended by the Developer such that turbines at Race
Bank shall not be built in areas intensively used by Sandwich terns (Centrica 2011b). This
targeted reduction in wind farm area together with the use of fewer, larger turbines reduces the
predicted collision risk at Race Bank. Figure 3.1 depicts two (non-shaded) „Tern Sensitive
Areas‟ on the western flanks of the Race Bank site boundary from which turbines are to be
excluded as these areas were identified as having a higher observed density of Sandwich tern
5 Case law (for example Rochdale MBC Ex. Parte C Tew 1999) provides a legal principle that indicative sketches and layouts cannot provide the basis for
determining applications for EIA development. The “Rochdale Envelope” is a series of maximum extents of a project for which the significant effects are
established. The detailed design of the project can then vary within this „envelope‟ without rendering the Environmental Statement inadequate.
6
from the boat based ornithological surveys. The maximum capacity of Race Bank (as
amended) would be 580MW instead of the 620MW applied for in 2009 (Centrica 2009).
Figure 3.1 Race Bank Offshore Wind Farm - showing the turbine installation (shaded red)
and Tern Sensitive Areas (unshaded areas) within the site boundary (black line)
(Source: Centrica 2011b)
3.8 The rationale underpinning the approach to Tern Sensitive Areas is, in effect, to not install
turbines in:
Areas where Sandwich terns regularly occur in higher concentrations, in comparison
to elsewhere on the site, in order to achieve maximum reductions in potential collision
risk;
Areas most likely to be encountered by birds on direct flight lines from the Scolt Head
and Blakeney Point colonies which is consistent with behaviour observed during
visual tracking (Centrica 2008, 2009 and Perrow et al. 2010, 2011); and
The edges of the site. Removing turbines in the centre of the site, rather than from the
edges, would mean birds must navigate turbines to reach open foraging habitat in the
centre of the site.
Smaller initial phase development at Docking Shoal
3.9 The Docking Shoal application has been amended by the Developer to reduce the initial phase
of the Development to a maximum capacity of up to 100 MW, comprising up to 20 (5 MW)
turbines. The development is proposed for a 29.82 Km2 area within the south-east corner of the
Docking Shoal site (shown shaded red in Figure 3.2) with a lower observed utilisation by
Sandwich terns (Centrica, 2011a), in order to minimise the collision risk to these birds (See
Table 7.1).
7
3.10 Figure 3.2 shows the area proposed for this initial phase development.
Figure 3.2. Docking Shoal offshore wind farm – proposed initial phase development area
(shown in red) (Source: Centrica 2011a)
3.11 Table 3.1 provides a brief description and construction programme for each project.
Table 3.1 Project description and indicative programme
Project
Parameter
Ma
x C
apacity
(M
W)
Tu
rbin
es
Foundations
Offs
hore
sub
sta
tions
Cabling
Fo
undatio
n
Constru
ctio
n
Tu
rbin
e
Insta
llatio
n
Com
mis
sio
n
Docking Shoal
(Phase I) 100 16 - 20
Monopile/ gravity base/ jacket
3 Inter-array and up to four export sub-sea cables laid using conventional ploughing or water jetting techniques with trenching, if resistant substrate is encountered.
2016-17 2017-18 2018
Docking Shoal
(Phase II)6
440 87 - 108
n/a n/a n/a
Race Bank
580
94 - 116
Monopile/ gravity base/ jacket
3 2014-2016
2015-2017
2015-2017
Dudgeon
560
85 - 168
Monopile/ jacket
7
3 2014-2015
2016 2016
Sources: Centrica 2008, 2009, 2011a, 2011b and DOW 2009, 2010.
Note: Programme dates are indicative and apply to the initial phase build only.
6 Subject to the views of the Ornithological Review Panel, further advice from JNCC and Natural England on likely significant effects and, finally, the
Secretary of State discharging the Grampian condition.
7 Dudgeon Offshore wind farm shall not use Gravity Based Foundations (DOW 2010).
8
3.12 The choice of turbine affects the predicted bird strike (collision risk mortality) at each project.
Developers have the option to use fewer and/or larger turbines in order to minimise collision
risk. The reduction in rotor swept area and/or slower rotational speed of the larger turbine
blades may reduce the predicted collision risk (see examples in Table 7.1).
3.13 If all three s36 applications are consented then each project is required to reduce bird mortality
(see Table 7.3 and Annex 1). DECC identifies that each project can be built in phases (if
necessary) using a 'Grampian condition' to allow the capacity of each project to be optimised.
Such a condition may permit subsequent phases of development within the development area,
up to the maximum consented capacity for that site, if evidence emerges that the modelling
used in this assessment (in particular the assumed avoidance rate) over estimates the
Sandwich tern mortality rate (i.e. the risk to the Sandwich tern population is lower than currently
predicted).
3.14 Alternatively, in order to reduce the predicted bird mortality, the Secretary of State may refuse
one of the applications with the result that the remaining projects can be constructed to their
maximum capacity in one phase (See Table 7.4 and Annex 2).
3.15 A project‟s turbine configuration will be limited by s36 consent conditions to a number and size
that would result in collision risk mortality no greater than that predicted by the collision risk
model used in this assessment (namely, ECON 2011a and ECON 2011b)8.
3.16 In order to discharge a Grampian condition and construct the remainder (or a proportion
thereof) of any project; each developer would have to do the following:
Provide evidence to show that the Sandwich tern collision mortality at Race Bank
(Phase 1), Dudgeon (Phase 1) and Docking Shoal (100 MW, Phase 1) is lower than
the predictions used in this Assessment and justify that further development,
considered alone and in combination with other projects, would not have an adverse
effect on the integrity of the North Norfolk Coast SPA;
Establish and seek the views of an Ornithological Review Panel9; and
Present the above information along with a request to discharge the Grampian
condition to the Secretary of State.
The Secretary of State may discharge the Grampian condition if:
He has received the above information;
He has, as the competent authority, taken advice from JNCC and Natural England,
which may differ from the view of the Ornithological Review Panel and may not be
limited to the effects on Sandwich terns;
He has, if advised to do so, completed a further Appropriate Assessment which
assesses further phases, alone and in combination with other relevant plans and
8 or agreed updates to this CRM
9 The Ornithological Review Panel would, as a minimum, consist of JNCC, Natural England, the RSPB and the Developer(s).
9
projects at that time, noting that the scope of any in combination effects may change
over time; and
He is satisfied that any other risks associated with discharging the condition to
construct further phases of each project are deemed acceptable.
3.17 DECC notes that Centrica submitted an application for a 540MW capacity wind farm at Docking
Shoal but subsequently made modifications to the original application in order to construct the
wind farm in phases, with a first phase not exceeding 100MW, in order to reduce the predicted
impacts of the proposed wind farm on the population of Sandwich terns of the North Norfolk
Coast SPA. This Appropriate Assessment will proceed on the basis that any initial phase of
development at Docking Shoal (should consent be granted) will be limited by DECC to no more
than 100MW as requested by the Developer.
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4 SCOPE OF THIS ASSESSMENT
4.1 Detailed analysis, consultation and discussion of environmental sensitivities took place prior to
this assessment regarding the interest features likely to be affected by each project. It has been
ascertained to the satisfaction of DECC, the MMO, JNCC10
and Natural England11
that an
Appropriate Assessment is required in respect of certain aspects of each project, but not others
(JNCC and Natural England 2010).
4.2 DECC may include mitigation measures which have been incorporated within an application
when deciding whether Appropriate Assessment is necessary12
. This assessment is made
subject to mitigation measures being secured, by condition, within the relevant consent or
licence for each project.
Sandwich terns
4.3 The projects lie within the foraging range of Sandwich terns (Sterna sandvicensis) from the
north Norfolk coast. JNCC and Natural England (2011a) advised that the potential bird strike at
each project, alone and in combination with other Greater Wash Offshore Wind Farms, may
increase annual mortality of Sandwich terns from the North Norfolk Coast SPA. DECC shall
amend each project, where necessary and within the Rochdale Envelope, to reduce the
predicted collision risk mortality.
4.4 JNCC and Natural England (2011a) advised that piling may displace the prey species of
Sandwich terns from each site. DECC has assessed this effect.
Harbour seals
4.5 Harbour seals (Phoca vitulina) (also known as Common seals) are an Annex II feature of The
Wash and North Norfolk Coast SAC. Harbour seals are protected during a closed season from
1st June to 31
st August under the UK‟s Conservation of Seals Act (1970). They are also listed as
a protected species under Appendix III of the Bern Convention (1979).
4.6 JNCC and Natural England (2011b) assert that female seals which haul out at Blakeney Point
within The Wash and North Norfolk Coast SAC may have to expend more energy foraging due
to the displacement of prey species during breeding season. DECC has assessed this
assertion to the best extent possible within the available evidence. DECC has also assessed
any displacement/barrier effect from underwater noise during construction.
4.7 JNCC and Natural England (2011b) advised that injury to Harbour seals from piling would not
be significant for each project provided suitable mitigation was in place. DECC notes that a
detailed Marine Mammal Mitigation Protocol (MMMP) shall be agreed with the MMO in
consultation with JNCC and Natural England prior to construction based on the latest inter-
agency protocol (JNCC 2010). This shall be a condition of any Marine Licence (MMO, 2012b).
10 JNCC advise on nature conservation effects at and beyond 12 nautical miles.
11 Natural England advise on nature conservation effects within 12 nautical miles.
12 Hart District Council v Secretary of State for Communities and Local Government & Ors [2008] (EWHC 1204).
11
4.8 JNCC and Natural England note that seal mortality in UK waters has been caused by extensive
spiral lacerations (‘corkscrew’ seal deaths). The Sea Mammal Research Unit (2010) believe
that the seal injuries are consistent with being drawn through a ducted propeller.
4.9 Until further evidence emerges JNCC and Natural England (2011b) requested that information
is presented to them regarding the potential use of ducted propeller vessels at each project.
JNCC and Natural England suggest that each ducted propeller vessel, of which there are
hundreds operating across the UK Continental Shelf including offshore support vessels, survey
vessels, fishing vessels, shuttle tankers, military vessels etc, may require a MMMP. The
Protocol may include one or more of the following:
Restrictions placed on the use of ducted propeller vessels during the Harbour seal
breeding season (1st June – 31
st August inclusive) and reduced ducted propeller use
when the vessel can feasibly moor or anchor;
Use of an Acoustic Deterrent Device whilst any ducted propeller is in use;
Monitoring, including shoreline stranding searches, whilst any ducted propeller is in
use; or
Vessels already fitted with guards would be preferable and should be considered as
alternatives (JNCC and Natural England 2011b).
4.10 The MMMP would record seal activity around any ducted propeller vessel and halt, subject to
navigational safety, the operation of the ducted propellers if, for example, a signature of an
injury was observed, a seal was deemed to be ‘at risk’ of injury or a carcass with corkscrew
injuries is stranded on the shore. JNCC and Natural England (2011b) note that, should a
signature of an injury be observed or a carcass is located, they would be likely to advise that
operations should be postponed subject to further advice. DECC concludes that there is
currently insufficient evidence that seal corkscrew deaths would be caused by wind farm
installation because contracts for construction vessels would not be awarded until consent is
granted. DECC and the MMO are content that likely significant effects on breeding Harbour
seals can be avoided or managed using a Marine Mammal Mitigation Protocol.
4.11 JNCC and Natural England (2011b) note that pupping and moulting seals could be disturbed at
the cable landfall for Docking Shoal and Race Bank. However there were no significant effects
recorded during the Lincs landfall operations or during hand worked cockle fishing (Natural
England 2010, EIFCA 2011a).
Grey seals
4.12 JNCC and Natural England (2011c) opined that Grey seals (Halichoerus grypus) from the
Humber Estuary SAC could be affected by piling noise. DECC notes that Natural England
(2011) advised ‘no likely significant effect’ for Westermost Rough Offshore Wind Farm which
lies 35km from Donna Nook. (Donna Nook is the location of the breeding Grey seal colony in
the Humber Estuary SAC). Docking Shoal and Race Bank lie 47 km and 42km, respectively,
from Donna Nook. The Secretary of State may have regard to mitigation measures which have
been incorporated within an application when deciding whether Appropriate Assessment is
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necessary. As a result, the Secretary of State concludes that piling activity at Docking Shoal
and Race Bank shall not have a significant effect on the integrity of Grey seals from the
Humber Estuary SAC for the following reasons
Given the shallow water depth at the mouth of the Humber and piling noise generated
at Docking Shoal and Race Bank would be expected to travel moderate distances.
Based on work undertaken at Barrow offshore wind farm it is predicted that the
temporary displacement from the pile-driving operations would be 7.5km (See table
6.1) with noise falling to background levels some 20km from the pile (Parvin et al.
2006). The distance between Docking Shoal and Race Bank (source of noise) and
Grey seals at Donna Nook (receptor) shall attenuate piling noise;
Grey seals at Donna Nook co-exist with a live RAF bombing range which is used
throughout the year (Natural England 2003);
The continued and long-term rise in the Grey seal population at Donna Nook (SCOS
2009); and
A detailed Marine Mammal Mitigation Protocol (MMMP) must be agreed with the MMO
in consultation with JNCC and Natural England prior to construction based on the latest
inter-agency protocol (JNCC 2010). This shall be a condition of any Marine Licence.
Annex I habitats
4.13 JNCC and Natural England advised that the Race Bank and Docking Shoal Offshore Wind
Farms may affect Annex I habitats, namely:
Sabellaria spinulosa reefs;
Saltmarsh;
Intertidal mudflats and sandbanks;
Inshore subtidal sandbanks; and
Offshore subtidal sandbanks.
Sabellaria spinulosa reef
4.14 In total, Centrica propose to route up to 10 export cables through The Wash. These cables shall
be installed within an indicative cable corridor. During baseline benthic surveys in The Wash,
Centrica identified the possible presence of S. spinulosa reef along the proposed cable corridor
for Docking Shoal and Race Bank. In response to the Draft Appropriate Assessment JNCC and
Natural England (2011c) reiterated that there may not be enough space within the cable
corridor for all 10 export cables. DECC notes the cable corridor is indicative and thus far wider
than the actual cables. Using the scale maps provided by JNCC and Natural England (2011b),
DECC estimates that the narrowest point between the edge of the cable corridor and Annex 1
S. spinulosa reef is approximately 1,700m. Centrica (2011g) state the 10 export cables would
be installed in 5 pairs of twin cables. The aim would be to maintain a separation distance of
150m between cable pairs where possible but this may be reduced or increased locally. The
13
distance between the twin export cables within each pair is planned to be nominally 50m apart,
but this may be reduced or increased locally due to wrecks, reefs or other micro-siting
requirements. The total width of the cables and separation distance is approximately 853m
(Centrica 2011g):
Cable separation (4 x 150m) + Cable pair separation (5 x 50m) + Cables (10 x 0.3m) = 853m
This is well within the confines of the narrowest point of the cable corridor (1,700m) adjacent to
the S. spinulosa biogenic reefs and can be narrowed, if necessary.
4.15 If Annex 1 S. spinulosa reefs are identified as part of the pre-construction surveys for any of
Centrica‟s projects in the Greater Wash then Centrica will micro-route the cable, within the
indicative cable corridor, around Annex I reef areas to avoid any effect (Centrica 2011d,
2011e). This commitment shall be a condition of any Marine Licence for both Docking Shoal
and Race Bank. Lincolnshire Wild Life Trust (LWT) also note the potential presence of S.
spinulosa reefs within the Race Bank site (LWT 2011). Consequently, the commitment to
survey and potentially micro-site to avoid Annex 1 S. spinulosa shall extend to turbines within
the Race Bank Offshore Wind Farm. This commitment shall be a condition of any Marine
Licence for Race Bank.
Suggested condition to avoid Annex 1 S. spinulosa reefs. Applicable to Docking Shoal and
Race Bank:
The Licence Holder must carry out a pre-construction survey to determine the
location and abundance of an Annex 1 habitat in the vicinity of the array and cable
route. Should an Annex 1 habitat be identified in the area of the proposed array and
cable route the licence holder is required to undertake an assessment of the need to
micro-site individual turbine structures, intra array cable or the export cable. If micro
siting is required the Licence Holder must inform the Licensing Authority
immediately. The results of the survey and assessment shall be submitted to the
Licensing Authority and Natural England within one month of the completion of the
survey and no construction is to commence without the written agreement of the
Licensing Authority.
4.16 DECC notes that Centrica have already installed the first Lincs export cable through The Wash.
DECC notes that Centrica (2011c) completed a S. spinulosa survey prior to installing the Lincs
export cables. The Lincs S. spinulosa survey confirmed that this polychaete is a common
macro-invertebrate species which is important in supporting several biotope and habitat
complexes in conjunction with a naturally complex geological profile for the Lincs site and
export cable corridor (Centrica 2011c). However, by applying the reef criteria classification
outlined by Gubbay (2007), with the exception of two sites both outwith the cable corridor, none
of the sites surveyed within the development area were classified as an Annex 1 biogenic reef
structure (Centrica 2011c).
DECC is content that the cable corridor is wide enough to permit micro-siting and Centrica
(2011c) have demonstrated via pre-construction surveys, during the installation of the Lincs
export cable, that S. spinulosa biogenic reefs can be identified and shall, as the condition
14
clearly states, be avoided. Accordingly, there will be no significant effects on Annex 1 S.
spinulosa reef.
Saltmarsh
4.17 The eight export cables from Docking Shoal and Race Bank shall pass through The Wash and
North Norfolk Coast SAC to landfall east of the mouth of the River Nene near Guy‟s Head. The
export cables from both Docking Shoal and Race Bank shall be installed beneath the salt
marshes of The Wash and North Norfolk Coast SAC using non-open cut methods. The
reception pit shall be set back, behind the first sea defence on agricultural land. There shall be
no significant effects on the salt marsh features of The Wash and North Norfolk Coast SAC.
4.18 DECC and the MMO note the difficulties to date with achieving cable landfall for the Lincs
export cable. Natural England opine that the proposed Horizontal Directional Drilling (HDD) for
the Docking Shoal and Race Bank export cables is not technically feasible. However, Centrica
(2011f) maintain that the following options are available:
Deep HDD;
Micro-tunnelling;
Impact moling;
Pipe ramming; and
Auger or thrust boring.
DECC notes that if Deep HDD, or an equivalent process such as micro-tunnelling, is not
successful then Centrica will be unable to fulfil this consent. If this occurs Centrica may, with
the consent of the MMO, be able to vary the Marine Licence to consider alternative methods of
crossing the salt marsh which would have to comply with the requirements of The Conservation
of Habitats and Species Regulations 2010 (as amended).
Suggested Marine Licence condition to install the Docking Shoal and Race Bank export cables
in the salt marsh using non-open cut methods only:
The Licence Holder must ensure that the export cables crossing the saltmarsh are
installed using non-open cut methods only. The ducts at the landfall will be installed
using non-open cut methods only.
The Licence Holder must submit and agree a detailed Cable Installation
Management Plan with the Licensing Authority at least four months prior to the
commencement of any cable/duct installation works crossing the saltmarsh.
Disturbance to passage and overwintering birds
4.19 Large numbers of migrating birds come to The Wash in the winter. The installation of the export
cables for Race Bank and Docking Shoal shall be subject to a timing restriction specifically to
avoid disturbing passage and overwintering birds. The MMO accept Natural England‟s advice
to restrict installation operations within the intertidal area to between the 01 May and 31 August
of any given year, unless otherwise agreed with the MMO and in consultation with Natural
15
England (JNCC and Natural England 2011b). This shall be a condition of any Marine Licence
for Docking Shoal and Race Bank. Consequently, there will be no significant effects on
passage and over-wintering birds in The Wash SPA. Additionally DECC understands that
progress on the installation of the export cable for Lincs offshore wind farm through The Wash
is progressing well and that sequential disturbance with cabling work for the Docking Shoal and
Race Bank projects is now unlikely (MMO, pers comm., 15th May 2012).
Onshore
4.20 This assessment does not address the effects of each onshore cable route (above mean high
water spring) which do not form part of these applications. Planning permission for the onshore
cable route for Docking Shoal and Race Bank (down to MHWS) has been obtained from King‟s
Lynn and West Norfolk Borough Council and South Holland District Council under Section 57 of
the Town and Country Planning Act (1990). Dudgeon‟s onshore cable route has been approved
by Breckland District Council and is subject to an application to North Norfolk District Council.
Other considerations
4.21 All cetacean species in UK waters are protected under Annex IV of the Habitats Directive.
DECC is satisfied that there will be no significant effects on marine European protected species
because a MMMP and „soft start‟ shall be a condition of any consent using piling. DECC notes
that further discussions will be required between the MMO, JNCC and the developer, post-
consent but prior to construction, to manage the risk of disturbance to cetaceans.
4.22 JNCC and Natural England (2011a) advised that there is no evidence to suggest a likely
significant effect on the Humber SPA and Gibraltar Point SPA so no Appropriate Assessment is
required for these sites. DECC agrees with this advice because the interest features of the
Humber SPA and Gibraltar Point SPA have not been recorded using the Docking Shoal, Race
Bank or Dudgeon sites with either a frequency or in numbers which suggest the likelihood of a
significant effect on either SPA.
16
Summary of scope
4.23 Only the following European interest features will be assessed further (Table 4.1):
Table 4.1 Likely significant effects – interest features ‘scoped in’ to this assessment
Project(s) Interest Feature Potential Effect
European Site
North
Norfo
lk C
oast
SP
A
Th
e W
ash a
nd N
orth
Norfo
lk C
oast S
AC
Inner D
ow
sin
g,
Race B
ank a
nd
North
Rid
ge c
SA
C
Docking Shoal
Race Bank
Dudgeon
Sandwich terns
Collision Mortality
Disturbance/displacement from feeding areas during construction
Displacement and reduction in prey availability during construction
Docking Shoal
Race Bank
Dudgeon
Harbour seals
Displacement/reduction of prey species for breeding females from Blakeney Point during construction
Barrier effect from cumulative construction noise
Race Bank Offshore sandbanks
Damage or destruction from turbine installation and associated vessels and scour protection
Damage or destruction from cable installation and vessel anchors
Docking Shoal
Race Bank
sub-tidal sandbanks
Damage or destruction from cable installation and associated vessels
Docking Shoal
Race Bank
Intertidal mudflats and sandbanks
Damage or destruction from cable installation and associated vessels
4.24 The following interest features are scoped out of this assessment (Table 4.2):
Table 4.2 No significant effect – interest features ‘scoped out’ of this assessment
Interest Feature Potential Effect Rationale
Sandwich terns
Barrier effect on flight lines from breeding colonies to feeding areas during operation
JNCC and Natural England advised that evidence from Scroby Sands and Zeebrugge wind farms suggests the barrier effect is unlikely to have a significant effect on the Sandwich tern population at the North Norfolk Coast SPA.
Displacement of prey during operation
JNCC and Natural England advised that evidence from Scroby Sands and Zeebrugge wind farms suggests the effect is unlikely to adversely affect the integrity of the Sandwich tern population at the North Norfolk Coast SPA.
Grey seals and Harbour seals
Injury or even death - if adults are in close proximity to piling at full energy
JNCC and Natural England advised that mitigation within each application is sufficient. Prior to piling, each applicant shall agree a Marine Mammal Mitigation Plan detailing:
17
Interest Feature Potential Effect Rationale
1. Marine Mammal Observer(s); 2. Soft start procedure; and 3. Acoustic Deterrent/ Harassment
devices. This commitment shall be a condition of any consent.
Sabellaria spinulosa Damage or destruction from turbines installation, cable installation and associated vessels
If core Sabellaria spinulosa reefs are identified as part of the pre-construction baseline surveys for any of Centrica‟s projects in the Greater Wash then Centrica will micro-route the cable around core areas to avoid any adverse effects (Centrica 2010). This commitment shall be a condition of any Marine Licence for both Docking Shoal and Race Bank.
Wintering, passage and breeding birds
Disturbance to overwintering and breeding birds during construction
Cable installation in the intertidal restricted to between 01 May and 31 August to avoid disturbance of breeding and over wintering birds. This commitment shall be a condition of any Marine Licence.
Saltmarsh communities
Damage or destruction from cable installation and associated vessels/vehicles
The saltmarsh shall be crossed using non-open cut methods. The launch/reception pit shall be located on agricultural land behind the first sea defence.
18
5 CONSERVATION OBJECTIVES
5.1 Neither the Offshore Marine Conservation (Natural Habitats, &c.) Regulations (2007) nor the
Conservation of Habitats and Species Regulations 2010 (as amended) define what is meant by
Conservation Objectives. However, Conservation Objectives outline the desired state for each
site in terms of the interest features for which they have been designated. When these interest
features are being managed in a way which maintains their nature conservation value, then
they are said to be in „favourable condition‟. An adverse effect on integrity is likely to be one
which prevents the site from making the same contribution to favourable conservation status for
the relevant feature as it did at the time of its designation (English Nature 1997).
5.2 The following paragraphs refer only to the European interest features which are within the
scope of this assessment.
5.3 Harbour seals – The Wash and North Norfolk Coast SAC (English Nature 2000, ESFJC
2008)
Conservation
Objective
Subject to change, maintain in favourable condition, the habitats of Common
seals, in particular intertidal mudflats and sandflats.
Risk Displacement/reduction of prey species for breeding females from Blakeney
Point during construction.
Measure Reduction, displacement and productivity of Harbour seals, measured
periodically using average count information.
Target A stable or increasing number of [breeding] Harbour seals, subject to natural
change.
5.4 Sandwich terns – North Norfolk Coast SPA (English Nature 2000, ESFJC 2008)
Conservation
Objective
To maintain, subject to natural change, Sandwich terns in favourable
condition, which is defined, in part, in relation to their population attributes:
a) Based on the known natural fluctuations of the population in the site,
maintain the population at or above the minimum for the site; and
b) Where the limits of natural fluctuations are not known, maintain the
population above 75% of that at designation – loss of 25% or more
unacceptable.
Risks a) Collision mortality;
b) Disturbance from feeding areas during construction; and
c) Displacement and reduction in prey availability during construction
from disturbance and physical injury or mortality caused by pile
driving.
Measure Reduction or displacement of birds and productivity (number of successfully
fledged young), measured periodically.
a) The population given on the citation (1989) is „up to 4500 pairs‟
19
(ESFJC 2008); and
b) SPA Review population 3457 pairs.
Target No significant reduction in numbers, in relation to baseline, subject to natural
change.
Citations published in 2001 by the JNCC state that the site qualifies under
Article 4.1 of the Directive (79/409/EEC) by supporting populations of
European importance of the following species listed on Annex I of the
Directive: Sandwich tern Sterna sandvicensis, 3,457 pairs representing at least
24.7% of the breeding population in Great Britain (5 year mean 1994-1998
(JNCC 2001a).
Although the citation apparently states a population up to 4,500 pairs, for the
purposes of this assessment the figure from the SPA review of 3,457 pairs is
used.
5.5 Offshore sandbanks – Inner Dowsing Race Bank and North Ridge cSAC (JNCC and
Natural England 2009)
Draft
Conservation
Objective
Subject to natural change, maintain or restore the feature in favourable
condition, such that:
a) The natural environmental quality is maintained;
b) The natural environmental processes are maintained; and
c) The extent, physical structure, diversity, community structure and
typical species representative of moderate diversity stable sand
communities are maintained, or restored where deterioration has
occurred.
Risks Damage or destruction from cable/pile installation.
Measure Extent, physical structure, diversity, community structure and typical species.
Target Subject to natural change, no change in extent of sub-littoral sandbank
sediment habitat allowing for natural variation or known cyclical change.
5.6 Subtidal sandbanks – The Wash and North Norfolk Coast SAC (English Nature 2000,
ESFJC 2008)
Conservation
Objective
Subject to natural change, maintain the sandbanks which are slightly covered
by seawater all the time in favourable condition, in particular:
a) Gravel and sand communities; and
b) Muddy sand communities.
Risk Damage or destruction from cable installation.
Measure Extent, sediment character, topography, distribution and extent of
characteristics biotopes, species composition.
Target No decrease in measures from an established baseline, subject to natural
change.
20
5.7 Intertidal mudflats and sandflats – The Wash and North Norfolk Coast SAC (English
Nature 2000, ESFJC 2008)
Conservation
Objective
Subject to natural change, maintain the mudflats and sandflats not covered by
seawater at low tide in favourable condition, in particular:
a) Sand and gravel communities;
b) Muddy sand communities; and
c) Mud communities.
Risk Damage or destruction from cable installation.
Measure Extent, sediment character, topography, nutrient enrichment, distribution and
extent of characteristics biotopes, characterising species diversity, community
structure and typical species.
Target No decrease in extent from an established baseline, subject to natural change.
21
6 HARBOUR SEALS – ASSESSMENT OF EFFECTS RESULTING FROM EACH PROJECT,
ALONE AND IN COMBINATION
6.1 The projects may have a likely significant affect on Harbour seals because:
Piling operations at Docking Shoal, Race Bank and Dudgeon may displace the prey
species of breeding female Harbour seals at Blakeney Point which may affect the
integrity of the population in The Wash and North Norfolk Coast SAC; and
Piling simultaneously at each project may cause a barrier effect which restricts Harbour
seals‟ access to haul-out beaches and foraging areas.
Background
6.2 The Harbour seal is one of only two species of seal that occur regularly within UK waters. The
Special Committee on Seals (SCOS) reported in 2010 that the total population of Harbour seals
in the UK is 26,650 individuals. The UK Harbour seal population has fluctuated dramatically,
particularly in The Wash. The Harbour seal population along the east coast of England (mainly
in The Wash) reduced by 52% following the 1988 phocine distemper virus (PDV) epidemic. A
second PDV epidemic in 2002 resulted in a decline of 22% in The Wash (SCOS 2008). The
population decline continued at 12-13% each year until 2007 (SCOS 2008). The Wash Harbour
seal population increased dramatically between 2007-2009 and is now 2,289, 7% below pre-
epidemic levels, with 372 Harbour seals observed hauled out at Blakeney Point during a single
survey in 2009 (SCOS 2010).
6.3 The population of Harbour seals breeding at Blakeney Point has continued to decline despite
the rise in Harbour seal numbers elsewhere in The Wash (SCOS 2008, 2010). This change
may be attributed to a significant shift in spatial distribution of breeding seals over the preceding
30 years with a much higher proportion of pups being found along creeks on the southern edge
of The Wash, mostly inside the RAF Danger Area at Wainfleet Range (Thompson 2007).
Observations suggest that Harbour seals appear to be excluded from the beach at Blakeney
Point when Grey seals are breeding and during the summer when the number of seal watching
boat trips tends to peak (Wood 2006, Skeate and Perrow 2008a).
6.4 The population of Harbour seals at Blakeney Point is subject to considerable natural change
due to disease. Competition from increasing numbers of grey seals and avoidance of seal
watching boats are cited as reasons that could be pushing Harbour seals from Blakeney Point
towards the banks of the Inner Wash, as a result the importance of Blakeney Point as a
Harbour seal breeding site is diminishing (Thompson 2007, Wood 2006, Skeate and Perrow
2008a, SCOS 2008, 2010).
Evidence from other sites
6.5 Evidence from other piled marine renewable installations indicates that the development of
wind farms in the Greater Wash is likely to be tolerated by Harbour seals.
22
Nysted &
Horns Rev
Denmark: Between 1999 and 2005 Harbour seals were studied at Nysted and
Horns Rev wind farms. Both Horns Rev and Nysted wind farms were part of
much larger foraging areas for seals. Approximately 12,000 Harbour seals haul
out on sites in the Wadden Sea c20km away and at Rødsand c4km from Nysted.
Detailed studies undertaken before, during and after construction indicated that
although there was a decrease in the number of seals present in the area during
pile driving there was no overall change in abundance during construction at
either site (Teilmann et al. 2006, Tougaard et al. 2006). No effects on Harbour
seals were observed after the wind farm was put into operation (DEA 2006).
Scroby
Sands
UK: Harbour seals continued to breed at a site 2km north of the piling operations.
Harbour seal pup production was notably low, in comparison to the baseline, at
the site before, during and following construction (E.ON 2004). The impacts of
severe storms during the 2004 breeding season, potential competition with
increasing numbers of Grey seals hauling out at Scroby Sands, disturbance from
the increasing intensity of seal watching boat trips and the continuing decline of
the UK Harbour seal population are cited as potential causes for the decline in
Harbour seals at Scroby Sands (E.ON 2004, Skeate and Perrow 2008b, SCOS
2008).
North
Hoyle
UK: There is a grey seal haul-out (non-breeding) on the West Hoyle Bank about
10km from the wind farm. Grey seal counts are undertaken monthly at the West
Hoyle Bank by the Hilbre Island Observatory. Data has been gathered here since
1964. Similar numbers of seals were recorded at this site during the pre-
construction, construction and post-construction phases of development, and
they concluded that there appeared to be no direct effect of the wind farm
construction on numbers of grey seals hauling out in the area (Npower 2008,
cited in SMRU 2009).
Lynn &
Inner
Dowsing
UK: Pile driving was intermittent lasting, on average, 2 to 3 hours per foundation
depending on ground conditions. Pile driving was separated by periods of a day
or more due to weather conditions and the time required to re-position, reset and
restart the piling vessel. A total of almost 85 hours were spent in acoustic
monitoring and over 82 hours were spent in visual observation. Thirteen marine
mammal sightings within sighting distance of the piling site; including 11 seals
and three porpoises. No sightings were made within 500 metres of the piling site
in the 30 minutes prior to proposed piling start time (RPS 2008). The protocol did
not require the Marine Mammal Observers to stay on site once piling started or
after dark, so no observations were made once piling was underway or at night.
SeaGen UK: SeaGen is a 1.2MW marine current turbine mounted on a quadropile
foundation in Strangford Lough. Strangford Lough is an important breeding and
foraging area for Harbour seals with small numbers hauling out to breed on
Cloughy Rocks which is less than 1km from SeaGen (Wilson 2005). SeaGen
23
commissioned both extensive and intensive monitoring programmes to observe
Harbour seals during the installation and operation of the device. Shore based
marine mammal surveys, telemetry studies and aerial surveys showed the overall
numbers of Harbour seals and pups did not decrease significantly in the
Strangford Lough SAC during either the installation or operation of SeaGen
(SeaGen 2009). The slight fluctuation was well within the natural population
variability.
Effects of piling activity - alone
6.6 Docking Shoal: The worst case scenario for noise from the full scheme at Docking Shoal is
driving 90 x 6.5m diameter monopiles. Docking Shoal lies in water depths of 3m to 14m below
(Chart Datum) CD, the seabed shallows to the south of the site over the Burnham Flats towards
the north Norfolk coast. DECC notes that the shallow water at Docking Shoal together with the
presence of Burnham Flats sandbank indicates a likelihood of substantial noise attenuation
between piling at Docking Shoal and Blakeney Point.
6.7 The potential displacement zones for seals around Docking Shoal have been calculated as
between 5km and 6km in waters less than 10m (Centrica 2008). This level of displacement
would only occur when piling at full energy. The Blakeney Point haul out site is also at a
sufficient distance to minimise potential impacts (12km to south-east); a peak to peak sound
level of 170dB re 1 μPa has been predicted at the shoreline and the perceived sound level
close to shore at Blakeney Point is estimated to be 75dBht (Centrica 2008). Harbour seals will
be aware of this level of noise; however, Harbour seals are thought to react (be displaced)
when noise increases above 90dBht (Nedwell and Howell 2004). As result, piling at Docking
Shoal (Phase 1) shall not displace Harbour seals.
6.8 Race Bank: The worst case scenario for noise from Race Bank is 96 x 6.5m diameter
monopiles. Race Bank lies in water depths of 5m to 20m below CD, at a distance of 27km from
Blakeney Point. Between Race Bank Offshore Wind Farm and Blakeney Point, lie three
substantial sandbank features; Race Bank, Docking Shoal and Burnham Flats. The likelihood is
that these large, shallow sandbank features will attenuate noise towards Blakeney Point. The
potential displacement for seals around Race Bank is calculated as 7.5km (Centrica 2009).
Piling at Race Bank shall not displace seals from the near shore water surrounding Blakeney
Point.
6.9 Centrica mapped the perceived sound levels detected by a variety of marine mammals,
including Harbour seals based on the noise emitted from driving a 6.5m pile. The Race Bank
Environmental Statement indicates that the unweighted peak to peak sound level at coastal
waters is predicted to vary from 140 - 145dB re 1μPa (Centrica 2009). The corresponding
perceived sound levels for Harbour seal would be around 40 - 45dBht in water 1km off the coast
(Centrica 2009). Harbour seals will be aware of this level of noise however, Harbour seals are
thought to react (be displaced) when noise increase above 90dBht. Piling noise is expected to
remain above 90dBht within 11.5km from piling at Race Bank so Harbour seals may be
displaced from this area during active piling (Centrica 2009). Race Bank is, at its closest point,
24
27km from Blakeney Point. Piling at Race Bank shall not disturb Harbour seals at Blakeney
Point.
6.10 Dudgeon: Dudgeon lies in water depths of 14m to 25m below CD and is located 38.8km from
Blakeney Point and has the lowest number of recorded Harbour seal sightings. The worst case
for piling noise from Dudgeon is the installation of up to 93 x 6.5m piles. The noise generated
during piling is predicted to displace seals up to 14km (DOW 2009). Dudgeon lies 38.8km from
Blakeney Point and 36km from Race Bank Offshore Wind Farm. DECC notes that the
substantial seabed features of Dudgeon Shoal and Sheringham Shoal would further attenuate
noise. Piling at Dudgeon shall not displace Harbour seals from Blakeney Point.
6.11 Table 6.1 summarises the relevant data relevant to each project.
Table 6.1 Summary of relevant piling data and effects from each project
Proposal
Pili
ng p
rogra
mm
e
Ma
xim
um
No.
of
6.5
m
mo
nopile
s
No
. o
f seals
(s
ite &
b
uff
er)
MM
MP
Te
mpora
ry T
hre
shold
S
hift
dis
tance (
km
)
Te
mpora
ry
dis
pla
cem
ent (k
m)
Te
mpora
ry
dis
pla
cem
ent
dis
tance w
ith n
ois
e
att
enuatio
n (
km
)
Dis
tance to B
lakeney
Poin
t (k
m)
Dis
tance to R
ace
Bank O
WF
(km
)
Docking Shoal (Phase 1)a 2016/17 16 71 0.35 10 6 12 14
Race Bankb 2014/16 96 25 0.35 11.5 7.5 27 -
Dudgeonc 2014/15 93 6 0.35 14 14 38.8 36
Sources: a) Centrica 2008, 2011a b) Centrica 2009, 2011b c) DOW 2009, 2011 pers comm.
Effects of piling noise on foraging behaviour of nursing Harbour seals
6.12 The key period of sensitivity for Harbour seals is in June and early July when adult females
bear a single pup. Harbour seals give birth on beaches that are often flooded at high tide so
pups normally enter the water within hours of being born (Knudston 1977). Studies of pups
equipped with time/depth recorders, which collect information on
diving behaviour, revealed that
suckling Harbour seal pups spend as much as 40% of their time in the water (Bekkby and
Bjorge 2000, Bowen et al. 1999). Pups swim and dive with their mothers, although they dive for
shorter periods compared with their mothers and need to haul out to rest more frequently than
mature seals (Bowen et al. 1999).
The need for pups to rest appears to restrict nursing seals to near shore waters with female
seals restricting their range markedly during the early (and most intense) part of lactation.
Nursing seals restrict their range to “nursery” waters within “a few kilometres” of the shore
(Bekkby and Bjorge 2000, Thompson et al. 1994, Lawson and Renouf 1985). As a result,
nursing seals and their pups will not be exposed to significant levels of piling noise (greater
than 90dBht) from Docking Shoal (Phase 1), Race Bank or Dudgeon which would displace them
from the waters immediately surrounding Blakeney Point during piling. Table 6.1 shows that
seals would not be displaced from the waters immediately surrounding Blakeney Point.
25
Effects of piling noise on foraging patterns of mature Harbour seals
6.13 The lactation period in Harbour seals lasts approximately 25 days so weaning is normally
complete by late July. After weaning, pups may not be able to catch enough prey to balance
their energy consumption for several weeks and rely on body fat reserves (Muelbert and Bowen
1993). As pups mature they haul-out less frequently as their endurance and thus foraging range
increases. Mature Harbour seals travel considerable distances to feed and range over a broad
area. Harbour seals tagged in The Wash by the Sea Mammal Research Unit normally foraged
within a 40-50 km radius around their haul out sites and travelled considerable distances
offshore to feeding grounds on trips lasting up to 6 days (Figure 6.1) (SCOS 2008, Thompson
and Harwood 1990).
Figure 6.1 Individual tracks of all Harbour seals captured and tagged by the Sea Mammal Research Unit around the UK between 2001 and 2005
(Reproduced with permission of Professor Philip Hammond, named author of Sharples et al. 2009)
Prey abundance
6.14 The availability of suitable foraging areas should be linked to contemporary analyses of the
seal‟s diet because Harbour seals switch their prey preference in relation to its local abundance
both within and between years (JNCC 2001b). Harbour seals are apex predators which take a
wide variety of prey including sandeels, gadoids, herring and sprat, flatfish, octopus and squid.
Seal diet varies seasonally and from region to region (SCOS 2008). SCOS (2008) observed, on
the basis of dive data and movements of tagged Harbour seals, that foraging occurred
throughout the movement range with wide ranging foraging trips to locate discrete „hotspots‟
followed by repeated foraging trips to these areas (Figure 6.2). This pattern suggests that
26
Harbour seals are opportunistic feeders, preferring feeding areas with high prey availability
rather than specialists seeking specific prey species (De Jong et al. 1997).
6.15 Harbour seal foraging patterns may change to follow fin fish but this movement will not be
outwith the existing foraging range of mature seals. Piling noise is unlikely to have a
discernable effect on benthic and shell fish species, which have a low sensitivity to noise.
However, piling noise has the potential to displace fin fish with swim bladders, over several
kilometres. Seals are unlikely to intensively forage in areas where prey is relatively scarce. The
overall prey resource available to Harbour seals is not expected to significantly diminish as a
result of piling but certain prey species, such as herring, may move. Given Harbour seal‟s
mobility, range and opportunistic diet, it is anticipated that the foraging patterns of Harbour
seals may change during piling operations to reflect changing patterns of prey availability.
Benthic and shell fish, which are part of the Harbour seals diet, will remain in close proximity to
piling activity.
6.16 Piling is not believed to affect Harbour seals‟ foraging ability. In clear waters seals are known to
hunt using their vision, which is similar to that of a domestic cat (BBC 1999). In turbid waters
Harbour seals use their highly sensitive mystacila vibrissae (whiskers) to analyse water
movements and locate prey species (Dehnhardt and Kaminski 1995, Hanke et al. 2010).
Harbour seal‟s mystacila vibrissae is sensitive enough to discriminate between objects of
different size or shape by their hydrodynamic signature and can even follow the weak water
movements left by prey that has passed (hydrodynamic trail following) (Hanke et al. 2010,
Wieskotten et al. 2011). Seals are not hearing specialists and are not known to rely on their
hearing to forage so piling noise should not impair Harbour seals ability to forage. Given the
mobility of mature Harbour seals and their hunting methods, it is unlikely that they would
encounter significant difficulties in finding alternative prey sources or foraging areas during any
temporary displacement of certain prey species during pile driving.
6.17 It is worth noting that Richardson et al. (1995) report that seals in both air and water tolerate
strong noise pulses from explosive and non explosive devices especially if attracted to an area
for feeding. For example, Acoustic Deterrent Devices (ADD) scare pinnipeds away from fishing
nets and fisheries through the emission of strong noise pulses. These devices have had some
success; Mate (1993) reports that whilst Harbour seals have been monitored to avoid nets
where ADD is in operation, the scaring effect decreases with time as individuals habituate to
the noise. Seals tolerate and habituate to anthropogenic noise once they realise that the noise
source is not a threat (Vella et al. 2001). The MMO notes that there is some evidence that
acoustic deterrent devices used with fishing nets may actually attract seals (who learn to
associate the noise with the presence of fish) and consequently any use of these devices within
the MMMP will need to be carefully considered and approved by the MMO.
6.18 It is possible that Harbour seals forage within each project site, however there is no evidence to
suggest that Docking Shoal, Race Bank or Dudgeon are of particular importance for Harbour
seals in relation to The Wash and North Norfolk Coast SAC. Rather Docking Shoal and Race
Bank lie within a broad area through which seals commute to foraging areas in The Wash (see
Figure 6.2). During two years of boat-based survey effort, no seals were observed foraging.
27
Whilst boat based observations do not provide an accurate indication of foraging activity, the
low numbers of seal sightings supports the assumption that Docking Shoal and Race Bank are
not key foraging areas for Harbour seals and seal usage of Dudgeon remains low.
6.19 JNCC and Natural England 2011c) raised concerns that consecutive years of piling could affect
prey availability. DECC notes that each project would be subject to herring spawning
restrictions to mitigate potential impacts from piling activity during a key period of the herring‟s
lifecycle. Preventing disturbance to spawning herring should ensure that herring recruitment
within The Wash is not adversely affected by the construction of each project and consequently
the herring stock available to seals is maintained over consecutive years. The suggested
herring spawning restriction is outlined in paragraph 7.44.
Effects of cable installation noise on Harbour seals
6.20 Noise measurements taken by Nedwell et al. (2004) during installation of the export power
cable by underwater plough at North Hoyle Offshore Wind Farm were approximately 178dB re
1μPa at 1m. This is below the level necessary to provoke any significant avoidance reaction,
even in hearing specialists such as cetaceans, so significant effects on pinnipeds such as
Harbour seals shall not occur.
Effects of vessel noise on Harbour seals
6.21 Construction and supply vessels accessing the Docking Shoal (Phase 1), Race Bank and
Dudgeon sites can be expected to use existing shipping lanes as far as possible. This would
have the effect of confining noise levels to areas that marine mammals already associate with
vessel noise, thus minimising the area impacted by vessel noise.
In combination effects
6.22 JNCC and Natural England advised that the construction schedule of the projects across The
Wash should be staggered to avoid any potential barrier effect. DECC notes that the
construction programme for Docking Shoal (Phase 1) (2016 - 17) does not overlap with piling
operations at either Race Bank (2014-16), Dudgeon (2014/15) or Triton Knoll (~2018/19). Piling
activity may overlap at Race Bank and Dudgeon; however, Dudgeon lies 36km to the east of
Race Bank. Furthermore, Dudgeon has recorded only six seals during two years of boat based
surveys which suggests the Dudgeon is of minor importance to Harbour seals.
6.23 JNCC and Natural England (2011c) noted that the assessment should consider the risk to
Harbour seals at sea. DECC sought further information from the SMRU who used existing
telemetry data from 25 Harbour seals to provide a proxy for Harbour seal activity within the
temporary displacement zones (see Table 6.1). Each temporary displacement zone extends
from the boundary of each site, as opposed to the centre (See Figure 6.2).
6.24 SMRU (2011) note that whilst there is an indication of decreasing numbers of seals traversing
the areas of interest in an easterly direction; there is an indication of more intensive usage in an
easterly direction. This may be because Docking Shoal and Race Bank (i.e. sites nearer The
Wash) are used more for travelling (hence low usage of many animals) whereas Dudgeon
(further away from The Wash) will not be crossed by as many seals but may be foraging
28
hotspots for particular seals (i.e. Dudgeon has higher usage by fewer seals). The results of
SMRU (2011) correspond to the seal numbers observed at each project (see Table 6.1).
Consequently, piling simultaneously at Race Bank and Dudgeon shall not create a barrier to
Harbour seal movement nor displace a significant number of Harbour seals from foraging
areas.
6.25 Other offshore industries: With reference specifically to Race Bank, no significant impacts are
envisaged as the only potential in combination effects are from shipping and aggregate
dredging. One dredging area (Dredging Area 107) is to the south west of Race Bank although
currently only a relatively small area of this site is intermittently dredged.
6.26 It is anticipated that any in combination impacts would be additional low-level pressures against
which effects would only be noticeable over the very long-term. These impacts would be difficult
to identify above natural variation.
Conclusion
6.27 Taking into account the amended applications, the mitigation proposed (soft start and the use
of a Marine Mammal Mitigation Protocol), the timing of construction programmes, the distance
to, and importance of, foraging areas, and the condition limiting development at Docking Shoal
(Phase 1), DECC concludes that the development at Docking Shoal (Phase 1), Race Bank and
Dudgeon Offshore Wind Farms, alone and in combination, shall not adversely affect the
integrity of the Harbour seal population within The Wash and North Norfolk Coast SAC.
6.28 DECC notes that the MMO proposes that monitoring will be required to validate the predictions
for the generation of underwater noise and the potential disturbance to Harbour seals and that
this monitoring will be a condition of any Marine Licence (MMO, 2012b).
29
(a)
(b)
Figure 6.2 The tracks of the 25 tagged seals which used The Wash as a haul-out, coloured by seal.
The extents of the tracks are shown (a) as well as the tracks around the areas of interest at a finer resolution (b). (Source: SMRU 2011)
30
7 SANDWICH TERNS – ASSESSMENT OF EFFECTS RESULTING FROM EACH PROJECT,
ALONE AND IN COMBINATION
7.1 Each project may affect Sandwich terns because:
The operation of each project may cause mortality due to collision with operational
turbines which in turn may reduce the North Norfolk Coast SPA population; and
Piling may displace/disrupt the life cycles of prey species and thus reduce prey
availability for breeding Sandwich terns.
Background
7.2 The UK Sandwich tern population is approximately 12,500 breeding pairs, however they exhibit
the most erratic population trends and distribution of any seabird breeding in the UK (JNCC
2011). The Sandwich tern population fluctuates dramatically among years owing to large
variations in the proportion of breeding birds whilst distribution varies due to mass movements
between colonies in the UK and across Europe (JNCC 2011). The North Norfolk Coast SPA
supports the largest, long-standing, breeding population of Sandwich tern in Great Britain. The
most recent estimates suggest the North Norfolk Coast SPA supports c. 40%, 5-6% and up to
2.8% of the national, European and global populations, respectively (Mitchell et al. 2004).
JNCC (2001) state that the North Norfolk Coast SPA supports 24.7% of the UK Sandwich tern
breeding population.
Evidence from other sites
7.3 Sandwich terns have been recorded at a number of operational Offshore Wind Farms. The
evidence from these studies have not identified any significant or adverse effects on Sandwich
tern populations.
Zeebrugge Belgium: Between 2001 and 2005 the Sandwich tern population at
Zeebrugge increased from between 920 breeding pairs to 2,538 peaking at
4,067 pairs in 2004 attributable to provision of artificial nesting habitat at the
colony. During this period 25 small to medium sized wind turbines were
operating along a seawall within 100 metres from the colony. Studies
undertaken between 2000 and 2005 included assessing the collision risk to
Sandwich terns from the wind turbines (Everaert 2003, Everaert and Stienen
2006, Everaert and Kuijken 2007). The studies concluded that the probability
of a Sandwich tern colliding with a turbine when flying at rotor height was
between 0.046% and 0.088%. Overall there was an additional increase (over
and above natural mortality) in Sandwich tern mortality of between 6% and
7% (JNCC/NE, 2012). The possibility that birds at Docking Shoal, Race Bank
and Dudgeon are more likely to be foraging in each area as opposed to
passing across the site and may therefore spend longer within the vicinity of
the turbines than the terns at Zeebrugge is accommodated in the passage
rate used in collision risk calculations.
31
Horns Rev Denmark: Extensive studies have been undertaken at the Horns Rev
Offshore Wind Farm in Denmark. A total of 4,726 Sandwich terns out of a
total of 8,747 terns were observed during the study; primarily during the
spring and autumn migration periods. The study noted that Sandwich tern
displayed no reaction to the turbines when entering the wind farm; whereas
avoidance behaviour was recorded in Arctic/Common terns (Petersen et al.
2006). Although significant behavioural reactions (i.e. avoidance) to the wind
farm and single turbines were not observed in any of the gull and tern
species, which dominated the birds observed within the area of the wind
farm, it was noted that birds were more likely to enter the wind farm between
two inactive turbines than they would if one or both were operating;
suggesting some degree of avoidance behaviour does occur (Petersen et al.
2006). The studies concluded that „Divers, gannet, common scoter, Auks,
Skuas, Gulls and Terns did not exhibit a high risk of colliding with the
turbines‟ and no collisions were recorded (Petersen et al. 2006).
Egmond aan
Zee
Netherlands: Egmond aan Zee lies 10km to 15km from the Dutch coast.
Extensive visual and radar studies showed that terns did not avoid the wind
farm and continued to forage within the operational wind farm. No collisions
were observed for any bird species and terns were observed entering the site
at stationary turbines suggesting some degree of avoidance does occur
(Lindeboom et al. 2011). The overall collision risk at Egmond aan Zee was
considered to be „low‟, based on observations and model calculations
(Lindeboom et al. 2011).
Thornton
Bank
Belgium: Thornton Bank Offshore Wind Farm lies approximately 35km from
the Belgian coast and is in an area frequently used by Sandwich terns,
particularly during the summer months when relatively high densities occur.
Unlike the studies at Zeebrugge; Sandwich terns at Thornton Bank are likely
to be foraging in the wind farm which is similar to projects subject to this
assessment. Monitoring results from Thornton Bank are surprising in that
Sandwich tern activity in the Thornton Bank wind farm area appears to have
significantly increased since the first turbines were built; numbers of
Sandwich terns in the wind farm increased by 30% whilst dropping in the
control area suggesting a possible attraction to the turbines (Veneram et al.
2011). Veneram et al. (2011) offer no reason for this apparent attraction to
the wind turbines but note that clear positive effects on fish communities are
already visible (Reubens et al. 2010). Collision Risk Modelling undertaken
using turbine encounter rates calculated using Bolker et al. (2008); the Band
model (2000) and an avoidance rate of 99.2% derived from Zeebrugge data,
suggested that there was a collision risk of 0.001%: i.e. there was one in a
one hundred thousand chance of a collision (Vanermen and Steinen 2009).
However, Veneram et al. (2011) conclude that the attraction of terns to the
32
Thornton Bank turbines should receive maximum attention in the coming
monitoring years although no collisions have been recorded.
Blyth UK: Two turbines were constructed 1km off the Northumberland coast. After
construction, 177 visual observations were carried out to determine the effect
of the turbines on seabirds, including Sandwich terns. Each observation
lasted approximately 2 hours and was carried out over a period of 32 months
when the turbines were operating. No observations were made after dark or
in poor daytime visibility. During this period, 2,135 Sandwich terns were
observed in flight, near the turbines. In summer, numbers of Sandwich terns
increased post-construction. No Sandwich terns collisions were recorded
(Rothery et al. 2009).
Collision Risk Model
7.4 The key measure of significance lies in a quantitative Collision Risk Model (CRM). This
Appropriate Assessment uses the Folkerts model. The Folkerts model combines the geometry
and rotational speed of the turbines, the dimensions and speed of the birds and other physical
conditions to predict the number of birds that could be struck if they exhibited no response to
the presence of the wind farm. The Folkerts model is a variant of the Band model which has
been adapted to better reflect the offshore environment, turbine characteristics and differences
between onshore „static‟ survey methods as opposed to mobile, boat based surveys used
offshore. SNH guidance recognises that the result of CRM should be moderated by an
avoidance rate to reflect that a high proportion of birds will take avoidance action (Band 2000,
Band et al. 2005).
7.5 In response to the Draft Appropriate Assessment, JNCC and Natural England (2011c)
requested clarification with respect to the validity of certain elements underpinning the CRM, in
particular:
The method of calculating in flight density;
The method used to account for non-SPA birds; and
Correction factors used in the Folkerts model when compared with the Band model.
7.6 Bird densities – survey methods: In the absence of any other information, all surveys from
September 2004 onwards at the Docking Shoal, Race Bank and Dudgeon sites undertaken by
ECON are assumed to have used the alternative radial survey method. DECC acknowledges
that the CRM must match the survey methods. Consequently the CRM is presented using the
radial survey method. DECC understands that most surveyors were ESAS trained and thus
liable to have incorporated birds at a greater distance than a radius of 300m.
7.7 Non-SPA birds: During the breeding season all terns recorded are assumed to be breeding
adults. Consequently any non-breeding adults originating from elsewhere, late-returning or
early-leaving breeding adults and failed breeders from elsewhere, are recorded as breeding
adults from the North Norfolk Coast SPA. In response to the Draft Appropriate Assessment
JNCC and Natural England (2011c) suggested that data should only be partitioned for
33
September and not for March and August. However, JNCC/NE (2011d) subsequently opined
that the correction factor for non-SPA birds “made very little difference to the collision risk.
Whilst it would be more precautionary if they were considered to be all from the SPA, we
believe it would be incorrect”. This correlates with earlier advice which acknowledged that
“some fraction of the birds recorded at sea…may not be birds from the North Norfolk SPA”
(JNCC/NE 2011a). A correction factor of 0.48 has been used on the predicted mortality rate for
the months of March, August and September to account for the majority of birds assumed not
to have originated from the North Norfolk Coast SPA during these months.
7.8 Collision Risk Modelling: JNCC/NE (2011c) assert that the Folkerts model produces different
results than the Band model with mortality figures between 17% and 48% lower than the Band
model (JNCC/NE, 2012). This is not surprising. Both models have conceptual and structural
differences. The Folkerts model makes the following assumptions which depart from the Band
model:
‘Mean distance across the site’ – In the Folkerts model this factor is used, with flight
speed, to calculate the number of flights across the site based on the density of birds
present.
‘Passing factor’ – a bird may fly across the site at rotor height but between the turbine
rows and thus never encounter a rotor. The Folkerts model calculates this probability by
modelling random, straight line passages through the site and determining the
proportion that pass through a rotor circle. In reality, the rotor is in a specific position
depending on wind direction. The bird may therefore pass through the rotor circle (i.e.
the circle representing all the possible positions which the rotor could occupy) but miss
the actual rotor because of its orientation. Both these elements are incorporated into
the „passing factor‟ which is therefore dependent on site layout and turbine size. This
factor is not actually represented explicitly in the Band model; and
‘Oblique flights’ – The Folkerts model makes the realistic assumption that the bird
may fly into the rotor at any angle between 0 and 90 degrees. It therefore includes a
numerical integration over all possible incident angles in order to calculate the collision
risk factor. Band recognises that this approach is valid as it is discussed in his draft
guidance document but concludes that it is an unnecessary sophistication. However,
the use of this factor is clearly a matter of expert opinion. Band does not identify any
major flaws in the Folkerts model which render the Folkerts model incorrect but
considers that it is likely to underestimate by a modest degree the collision risk at
oblique approach angles (JNCC/NE, 2012).
7.9 DECC notes the MMO has commissioned an independent review of the Folkerts model. The
results identify that the Folkerts model is considered to be scientifically robust and the use of
the model to assess the collision risk for the Greater Wash wind farms is sound. (MMO, 2012).
7.10 DECC believes that the collision risk model is valid and robust and appropriate for this
assessment for the following reasons:
34
The Folkerts model was developed specifically for offshore sites;
The model uses extensive and relevant bird data sourced from observations of
Sandwich tern foraging behaviour off the north Norfolk coast including birds followed at
sea to record their flight behaviour and use of foraging areas;
The model takes account of site specific factors – such as the individual turbine layout
at each site, the recorded wind speeds (which determines how often and at what speed
the turbine blades will turn), the predicted down time for turbine maintenance (when the
blades will not be turning), the number of birds that can be expected not to be breeding
birds from the North Norfolk Coast colonies (such as passage birds at the beginning
and end of the season).
Avoidance Rate
7.11 The output of the CRM is particularly sensitive to assumptions about the avoidance rate. A
difference of, for instance, 0.5% can make a noticeable difference to the number of bird strikes
predicted and can therefore affect whether there is predicted to be an adverse effect on the
integrity of a site or not (Chamberlain et al. 2006). The avoidance rate is critical in determining
whether there is likely to be an adverse effect on the Sandwich tern population. The avoidance
rate must be based on the best available evidence. There has been a considerable amount of
discussion between DECC, JNCC and Natural England regarding the evidence available and
the most appropriate avoidance rate to use when undertaking this assessment.
7.12 The Appropriate Assessment undertaken for Sheringham Shoal used, on the evidence
available at the time, an avoidance rate of 99.6% (BERR 2008). This was based on calculations
made from data collected at Zeebrugge Wind Farm, where the turbines lie on a seawall
between the Sandwich tern colony and the sea. Consequently Sandwich terns must cross a line
of turbines to forage at sea. A review undertaken by Whitfield in 2008 recalculated the
avoidance rate from data collected at Zeebrugge as 98.9%. However, the review concluded
that an avoidance rate of ≥99% for Sheringham Shoal, where Sandwich terns are largely
passing through the site, was reasonable but suggested a more precautionary 98% avoidance
rate for other Offshore Wind Farms where Sandwich terns may be foraging (Whitfield 2008).
JNCC and Natural England (2011a) completed a further review of the Zeebrugge data which
indicated that the inter-annual avoidance rate lies between 98.46% and 99.20%.
7.13 DECC presents a range of avoidance rates, to illustrate how sensitive the Collision Risk Model
is to assumptions about the avoidance rate, but concludes this Appropriate Assessment based
on JNCC and Natural England‟s conclusion that the most appropriate estimate of the mean
avoidance rate from the Zeebrugge data is 98.83% (JNCC and Natural England 2011a).
7.14 DECC believes that the avoidance rate used is appropriate for this assessment for the following
reasons:
The rate is based on empirical data from observations of tern mortality;
The value used is the mean value of data collected over two years;
35
The dataset from which the rate is derived has been peer reviewed and is considered
one of the best empirical datasets currently available for Sandwich terns (JNCC/NE
2011a).
Population Viability Analysis
7.15 JNCC and Natural England (2011a) made a recommendation to DECC regarding an
acceptable level of mortality for Sandwich terns. In arriving at their recommendation, JNCC and
Natural England referred to the Population Viability Analysis (PVA) model, developed
specifically to assist in forecasting the potential population impacts on breeding Sandwich terns
at the two principal breeding colonies, Scolt Head and Blakeney Point, within the North Norfolk
Coast SPA (Mackenzie et al. 2011).
7.16 The Sandwich tern population parameters which fed into the PVA were determined using
historic data from the North Norfolk Coast colonies and ringing studies based on all UK
Sandwich tern recoveries. Historically, there has been considerable inter-annual variation in the
occupancy of the tern colonies at Scolt Head and Blakeney Point. The factors responsible for
colony switching are not fully understood but might include changing prey availability in The
Wash in different years and the effects of kleptoparatism by black headed gulls (Mackenzie et
al. 2011). Predators such as foxes may have large effects on colony productivity in some years
as may poor weather; such catastrophic events are incorporated into the PVA (Mackenzie et al.
2011).
7.17 As with any ecological model; the PVA contains uncertainty and makes certain assumptions.
Firstly, the model simulates fluctuation within a „closed population‟ of breeding Sandwich terns.
The reality is somewhat more complicated by emigration/immigration. Ringed birds from other
colonies have been recorded at Scolt Head and Blakeney Point (ECON 2011a). Furthermore,
the exact origin of many birds is difficult to determine, with Sandwich terns from breeding
colonies in Denmark and the Netherlands likely to cross the North Sea at this time, with the
possibility of reciprocal transfer of birds from UK colonies (Wernham et al. 2002). Finally, non-
breeding Sandwich terns would have been observed during boat based surveys within the
breeding season.
7.18 JNCC and Natural England (2011a) recommended that DECC use a maximum mortality
threshold of 75 birds per annum for Sandwich terns noting there is no obvious cut-off point
within the PVA model. JNCC and Natural England based their advice on: the absolute risk to
the population (i.e. the probability of the population experiencing a decline), the increase in risk
to the population (the increase in probability compared to the no-wind farm scenario) at a range
of three threshold levels, and finally a consideration of when the statistical comparisons
conducted indicated the probability to be significantly different from the no-wind farm scenario.
7.19 JNCC and Natural England recommended that the absolute risk to the Sandwich tern
population should be less than 66% (JNCC/NE, 2011a) at which point a decline in the
Sandwich tern population may be described as „likely‟, based on IPCC guidance on dealing with
uncertainty (IPCC 2005). Based on a reference population of 6914 individuals, JNCC/NE note
that the mortality of 75 birds per year suggests an “about as likely as not” (62.6%) probability of
36
the Sandwich tern population declining below the reference level; the mortality of 100 bird
suggests a “likely” (66.9%) probability of decline below the reference level (6914 individuals).
On this basis, the upper mortality threshold lies between 75 and 100 terns each with a
probability of decline between 62.6% and 66.9%, respectively. Interpolating between these two
points suggests the upper mortality threshold (66%) is 94.8 birds. DECC shall, for the purposes
of this assessment, use an annual mortality threshold of 94 (i.e. <66%).
7.20 DECC considers that the population viability analysis is robust and a mortality threshold of 94
Sandwich terns is appropriate because:
The mortality threshold chosen (94 Sandwich terns) meets the criteria for absolute risk
(“less than 66%”) suggested by Natural England / JNCC;
JNCC/NE (2011a) note that the PVA model predicts that after 25 years the loss of an
additional 75 birds per year from the breeding population will result in the SPA
population being circa 4% lower than the current designated size of 6914 birds and that
the Sandwich tern population at the North Norfolk Coast SPA could sustain an upper
limit to annual mortality (from wind turbine collisions) of 75 terns without having an
adverse impact on site integrity. On this basis the loss of 94 birds per year will result in
the SPA population being 4.76% lower than the reference population, this is only 0.76%
higher than the loss predicted with an annual harvest of 75 birds. DECC considers that
this slight increase is acceptable;
The PVA model is appropriate for these tern colonies. The PVA was commissioned by
Centrica at the request of NE/JNCC specifically to model the Sandwich tern population
of the North Norfolk Coast SPA. The model was independently reviewed in 2011 (the
Stillman Review) and the model was revised to reflect recommendations in that review.
The RPSB and NE/JNCC have been actively involved in the development of the model;
The PVA model is robust. The tern colonies are a well studied breeding population with
reliable and long term data (predating the designation of the SPA). The model uses
empirical data collected over several decades to reflect the number of breeding pairs
and the fledging rate (breeding success) of terns in these colonies. The potential for
catastrophic natural events affecting breeding success is accounted for by sampling
observed fledging success;
The PVA authors suggest a loss after 25 years (i.e. operation of wind farms) of 5% to
10% of the reference population size might be regarded as offering a reasonable
chance of retaining population and site integrity (Mackenzie et al. 2011). This equates
to an annual harvesting level of 98 to 157 birds, which is considerably in excess of the
DECC 94 bird threshold; and
JNCC/NE‟s harvest level was presented and calculated in increments of 25. DECC has
calculated the harvest level to the nearest number, rounding down to the nearest whole
number.
37
Taking all these issues together, in particular the advice from JNCC / NE and the PVA authors,
DECC considers that an annual 94 Sandwich tern mortality rate is a credible threshold on which
to base its assessment of wind farm development applications in the Greater Wash whilst
ensuring that the integrity of the Sandwich tern population is not adversely affected.
Increase in risk
7.21 JNCC and NE advised that the conservation objective of maintaining the population would not
be compromised provided there is:
No more than a 10% increase in the probability of the population experiencing a decline
of 10% or more
and
No more than a 5% increase in the probability of the population experiencing a decline
of 20% or more
and
No more than a 2% increase in the probability of the population experiencing a decline
of 50% or more.
7.22 Evidently the higher the mortality rate, the greater the risk of the Sandwich tern population
declining but the PVA model indicates that the increase in risk to the population associated with
a 94 bird threshold (as opposed to a 75 bird threshold) is only very slight. Using a mortality
threshold of 94 birds per annum there shall be:
No more than a 12% increase in the probability of the population experiencing a decline
of 10% or more (this is 2% higher than the views of JNCC and Natural England 2011a);
and
No more than a 7% increase in the probability of the population experiencing a decline
of 20% or more (this is 2% higher than the views of JNCC and Natural England 2011a);
and
No increase in the probability of the population experiencing a decline of 50% or more
(this accords with the views of JNCC and Natural England 2011a).
7.23 DECC considers the 2% increase in the probability of the population experiencing a decline of
10% or 20% is marginal and acceptable when considered in light of the precaution within the
PVA model and CRM (paragraph 7.39).
Collision risk at each project
7.24 DECC notes that the CRM for Docking Shoal, Race Bank and Dudgeon utilises site specific
data as agreed with JNCC and Natural England at the meeting held by DECC on the 24th June
2011, including: wind speeds derived from the Race Bank meteorological mast; the actual cut-
in speed of commercially available turbines; mean rotor speeds of these commercially available
turbines and downtime owing to scheduled maintenance, derived from another Offshore Wind
Farm in the Greater Wash. This presents an accurate representation of the likely turbine
operation which results in minor changes to potential mortality (ECON 2011a, 2011b).
7.25 DECC acknowledges that the CRM must match the survey methods. Table 7.1 summarises the
potential mortality for Sandwich terns from the North Norfolk Coast SPA for each project and
the total, in combination, in the Greater Wash when using a bird density snap shot area of
0.141km2.
38
Table 7.1 Summary of Sandwich tern collision risk predictions for birds from the North
Norfolk Coast SPA from Greater Wash Offshore Wind Farms using a
snap shot area of 0.141 km2
Site Turbine layout Avoidance rates
0 98 98.46 98.83 99 99.2 99.6
Docking Shoal (Phase I - 100 MW)
16 x 6.15 MW (126m) 1217 24 19 14 10 9 5
16 x 6.15 MW (145m) 1121 22 17 13 11 9 4
16 x 6.0 MW (155m) 1181 24 18 14 12 9 5 13
20 x 5MW (128m) 19 14 12 10 5
16 x 6.15MW (152m) 18 13 11 9 5
16 x 6.0MW (145m) 16 12 11 8 4
16 x 6.0MW (154m) 17 13 11 9 4
Docking Shoal (Phases I and II - 540 MW)
87 x 6.15 MW (126m) 7293 146 112 85 73 58 29
87 x 6.15 MW (145m) 6719 134 103 79 67 54 27
90 x 6.0 MW (155m) 7322 146 113 86 73 59 29 14
108 x 5MW (128m) 113 86 74 59 29
87 x 6.15MW (152m) 105 80 68 55 27
90 x 6.0MW (145m) 101 76 65 52 27
90 x 6.0MW (154m) 106 80 69 55 27
Race Bank (Exc. Tern Sensitive Areas) (580 MW)
94 x 6.15 MW (126m) 4175 84 64 49 42 33 17
94 x 6.15 MW (145m) 3863 77 59 45 39 31 15
96 x 6.0 MW (155m) 4156 83 64 49 42 33 17 15
96 x 6.0MW (145m) 57 43 37 29 15
94 x 6.15MW (152m) 60 46 39 31 16
96 x 6.0 (154m) 60 45 39 31 15
116 x 5MW (128m) 64 49 42 33 17
Dudgeon (560 MW)
168 x 3 MW 3698 74 57 43 37 30 15
118 x 3 MW 2597 52 40 30 26 21 10
120 x 3.6 MW 2517 50 39 29 25 20 10
85 x 6.15 MW 2229 45 34 26 22 18 9
Sheringham Shoal (317 MW) 88 x 3.6 MW 1124 22 17 1316
11 9 5
Triton Knoll (1,200 MW)
17333 x 3.6 MW 729 15 11 9
18 7 6 3
19288 x 3.6 MW 14 10 8 7 6 3
240 x 5 MW - - - - - - -
150 x 8 MW - - - - - - -
Total (Docking Shoal 540MW)
292 219 166 142 114 54
Total (Docking shoal 100MW)
158 135 102 87 71 36
Sources: Scira Offshore Energy 2006, ECON 2011a, 2011b, Centrica 2012 Notes: The values shown in the Total rows use the best performing configurations
7.26 Table 7.1 shows Race Bank as amended by the developer to exclude turbine build within areas
identified as preferentially used by foraging Sandwich terns (see section 3.7) and with and
without a full scheme at Docking Shoal. DECC notes that the 100MW Docking Shoal scheme is
deployed so as to avoid areas with the highest bird densitiies. The values highlighted in bold in
the Table represent the best case collision risk values from the turbine configuration options
presented by the developers.
13
Additional turbine data supplied by Centrica 18/1/12
14 Additional turbine data supplied by Centrica 18/1/12
15 Additional turbine data supplied by Centrica 18/1/12
16 ECON completed the CRM for Sheringham Shoal so the collision risk is assumed to follow a snapshot area of 0.141km2.
17 See text at section 7.28
18 RWE nPower state that their CRM is already based on a snapshot area of 0.141km2 so no further changes are made. JNCC confirmed that the CRM
presented in both the Draft Appropriate Assessment and this assessment are correct (JNCC/NE 2011d)
19 Details for 98% and 98.83% taken from the Triton Knoll offshore wind farm “Report to inform Habitats Regulations Assessment January 2012 Rev B”. Other values
interpolated from the 333 turbine values and rounded up to nearest whole bird
39
7.27 DECC notes that a total of 29 surveys were conducted between March 2004 and February
2006 at Sheringham Shoal (Scira 2006). ECON assumed responsibility for boat based surveys
in September 2004. Consequently the CRM results from Sheringham Shoal have been
corrected to reflect ECON‟s survey methods. JNCC and Natural England (2011d) advised
DECC that the Sheringham Shoal CRM should, in the absense of further information, be 20%
higher than the figure used in the draft Appropriate Assessment (September 2011).
Consequently the predicted mortality rate at Sheringham Shoal has been raised from 11 to 13
birds.
7.28 JNCC and Natural England (2011a) recommended that some consideration be given to Triton
Knoll as the project has completed data collection and is expected to enter the planning system
towards the end of 2011. DECC notes that the application was accepted at end February 2012
for consideration by the IPC (now the National Infrastructure Directorate within the Planning
Inspectorate). DECC has included Triton Knoll within the in combination assessment using the
CRM figures submitted by RWE to the National Infrastructure Directorate and based on an
applied for configuration of 288 x 3.6MW turbines and previous discussions between DECC
and RWE npower renewables (RWE npower 2011). DECC notes that this configuration equates
to a maximum capacity of 1037MW. DECC is aware that RWE has now indicated that they do
not seek to build a 333 x 3.6MW turbine configuration but do still seek to build up to a maximum
capacity of 1200MW, eg. with a configuration of 195 x 6.15MW turbines (RWE, 2012). DECC
does not have collision risk model data for a 195 x 6.15MW turbine configuration at Triton Knoll.
7.29 The total mortality across all five projects in combination (and using the restricted (100MW)
deployment at Docking shoal) is predicted to be 102 Sandwich terns using the best performing
(lowest tern kill) turbines and 127 terns per annum, using the worst case collision risk figures
from each project. The projects in combination shall not exceed a mortality threshold of 94 terns
per annum. Consequently the projects must be amended to reduce the annual mortality rate of
Sandwich terns or a project must be refused such that the remaining projects shall not exceed
the mortality threshold of 94 Sandwich terns.
7.30 DECC has made no attempt to amend Sheringham Shoal which is under construction. The
Triton Knoll application is now being considered by the National Infrastructure Directorate.
DECC has identified that the Sandwich tern mortality for this site will need to be amended to
meet the overall 94 bird mortality limit if all three s36 projects are to be consented.
7.31 In DECC‟s view one way to proceed is to require a reduced phase 1 construction for each of
the three s36 applications proportionate to the bird mortality impact of each project.
Alternatively, the Secretary of State may refuse a project so that the remaining projects can be
consented to their maximum capacities without restricting the size of the initial build.
7.32 In terms of effects, the closer a project lies to the Sandwich tern colony and the foraging areas
used by Sandwich terns the greater the risk of bird strike. Annex 1 shows restrictions applied to
all schemes with Docking Shoal making the largest reduction in proportion to its capacity,
followed by Race Bank, Dudgeon and Triton Knoll (without prejudice to the consideration of this
application by the Planning Inspectorate). Annex 1 allocates reductions to projects in proportion
40
to the number of Sandwich terns each project may kill (as predicted by the collision risk model)
– i.e. the larger the impact the greater the reduction in mortality required.
7.33 Annex 2 shows the allocation of bird mortality assuming that the Docking Shoal application is
refused. Due to its location in an area used by foraging Sandwich terns Docking Shoal has the
highest predicted kill rate per turbine of any of the five sites considered in this Assessment.
Using the best case collision risk figures, and including the performance improvements from a
reduced size Docking Shoal scheme, on average an operational turbine at Docking Shoal has a
predicted annual mortality (assuming a 98.83% avoidance rate) 65% greater than that for a
Race Bank turbine and 150% greater than that for a Dudgeon turbine. These data are shown at
Table 7.2.
Table 7.2: Predicted best-case annual average Sandwich tern mortality per turbine (assuming
98.83% AR)
Project Birds killed Turbines Bird mortality (per turbine)
Docking Shoal (540MW) 76 90 0.844
Docking Shoal (Phase I) 12 16 0.750
Race Bank 43 96 0.448
Dudgeon 26 85 0.306
Sheringham Shoal 13 88 0.148
Triton Knoll 8 288 0.028
7.34 Table 7.3 shows the Sandwich tern mortality across all three s36 applications with the reduction
in combined mortality being delivered by the imposition of limiting conditions in the s36 consent
(should this be granted). In-combination with the collision risk model mortality values for the
consented Sheringham Shoal wind farm and the proposed values at Triton Knoll the upper
annual mortality threshold of breeding Sandwich terns from the North Norfolk Coast SPA is
calculated as 94 birds.
Table 7.3 Proposed allocation of Sandwich tern mortality (based on an avoidance rate of
98.83%) assuming all three s36 applications consented
Wind farm Limit on
Sandwich tern
mortality
(birds killed
per annum)
Illustrative example Site max
capacity
applied for (s36
application)
No. of
turbines
Turbine type Effective
site max
capacity
41
Wind farm Limit on
Sandwich tern
mortality
(birds killed
per annum)
Illustrative example Site max
capacity
applied for (s36
application)
No. of
turbines
Turbine type Effective
site max
capacity
Docking Shoal 10.9 14 6.0MW (145m) 84MW 100MW (first
phase, 540MW
total)
Race Bank 39.1 87 6.0MW (145m) 522MW 580MW
Dudgeon 23.7 77 6.15MW 474MW 560MW
3 wind farm
total
73.7 1080MW 1680MW
Sheringham
Shoal
13 88 3.6MW 317MW 315MW
Triton Knoll 7.3 262 3.6MW 943MW 1200MW
5 wind farm
total
94 2340MW
Note: The number of turbines and turbine type are illustrative only. The developer is able to deploy any turbine type
provided that the limit on annual bird mortality for that site is not predicted to be exceeded. The examples shown are
the best performing turbine options (generating the most MW for each bird killed) chosen from the turbine
configurations and collision risk mortality data presented to DECC for the s36 applications.
7.35 If the application for Docking Shoal is refused DECC identifies the bird mortality allocation
shown in Table 7.4 with the Race Bank, Dudgeon, and Triton Knoll applications consented to
their maximum capacities.
7.36 DECC ackowledges that other allocations of Sandwich tern mortality may be compliant with the
conclusions of this Appropriate Asesessment (such as consenting all three s36 applications but
applying constraining conditions onto only two applications) provided that the predicted
Sandwich tern mortality considered from all of the sites in-combination does not exceed the 94
bird annual mortality threshold.
42
Table 7.4 Proposed allocation of Sandwich tern mortality (based on an avoidance rate of
98.83%) assuming the Docking Shoal application is refused
Project Sandwich tern mortality
Configuration
Proposed Sandwich tern mortality
Illustrative revised turbine configuration
Illustrative max capacity
Race Bank 43 96 x 6.0MW 43 96 x 6.0MW 576MW
Dudgeon 26 85 x 6.15MW 28 91 x 6.15MW 560MW
Total (2 sites)
69 71 1136MW
Sheringham Shoal
13 88 x 3.6MW 13 88 x 3.6MW 317MW
Triton Knoll 8 288 x 3.6MW 9 333 x
3.6MW20
1199MW
Total (4 sites)
90 2452MW 93 2652MW
Note: The number of turbines and turbine type are illustrative only. The developer is able to deploy any turbine type
provided that the limit on annual bird mortality for that site is not predicted to be exceeded. The examples shown are the
best performing turbine options (generating the most MW for each bird killed) chosen from the turbine configurations and
collision risk mortality data presented to DECC for the s36 applications.
7.37 Tables 7.3 and 7.4 show that no project, when considered alone, shall have an adverse effect
on the integrity of the Sandwich tern population of the North Norfolk Coast SPA, when using an
avoidance rate of 98.83%, as the mortality of any project, alone, does not exceed 94 birds per
annum.
7.38 Table 7.1 shows that, excluding all mitgation, the projects would, as amended by the Developer
and in combination, exceed the mortality threshold of 94 Sandwich terns. However, either by
reducing capacity at each site so that the predicted mortality of all projects, in combination, will
not exceed 94 birds per annum (Table 7.3) or by refusing the Docking Shoal application and not
reducing capacity at the remaining sites, the predicted mortality of all consented projects in
combination will not exceed 94 birds per annum (Table 7.4).
7.39 DECC considers that a predicted mortality of 94 Sandwich terns per annum is precautionary
because:
All of the predicted mortality in April, May, June, and July is attributed to breeding terns
from the North Norfolk Coast SPA. This overstates the impact on the SPA breeding
population here as some of the mortality will occur to birds on passage to other
colonies, and to juveniles and non breeding adults from the North Norfolk Coast SPA.
Similarly some of the mortality in the later months will be post-breeding adults
dispersing from other colonies; and
20
Without prejudice to the conclusion of the Planning Inspectorate consideration of the Triton Knoll application and noting that RWE has stated that it now
does not seek to build this configuration (see section 7.28)
43
The predicted mortality at Sheringham Shoal has been increased by 20% (from 11 to
13 birds) on the precautionary assumption that the bird survey methods may have
underestimated bird densities at the site.
Conclusions
7.40 Based on the evidence from other sites, with the proposed mitigation measures applied and
assuming an avoidance rate of 98.83%, it is possible to conclude both that:
Race Bank and Dudgeon may be consented to their maximum capacity without
restriction on their initial build and shall not adversely affect the integrity of the
Sandwich tern population of the North Norfolk Coast SPA either alone or in combination
with Sheringham Shoal and Triton Knoll offshore wind farms provided that the Docking
Shoal application is refused; and
With the limits on Sandwich tern mortality applied Docking Shoal (as proposed by the
developer and limited to a capacity not exceeding 100MW), Race Bank and Dudgeon
shall not adversely affect the integrity of the Sandwich tern population of the North
Norfolk Coast SPA, either alone or in combination with Sheringham Shoal and Triton
Knoll Offshore Wind Farms.
7.41 DECC notes the intention of the MMO to require a monitoring programme, as a condition of any
Marine Licence, to validate the avoidance rate used to inform this assessment (MMO, 2012b).
Disturbance of Sandwich terns from foraging sites during construction and
displacement and reduction in prey availability
7.42 JNCC and Natural England advised that there is a likely significant effect because Sandwich
terns may have to increase their energy expenditure to find suitable prey in alternative foraging
locations during the construction period, as a result of piling potentially displacing prey species.
This may result in reduced adult fitness and/or reduced productivity of Sandwich terns as a
result of lower prey delivery rates to young. JNCC and Natural England identified a potential in
combination effect on prey-species should more than one wind farm be constructed at the
same time and noted the CEFAS recommendations regarding time restrictions on piling during
sensitive periods for herring. Natural England and JNCC advised that following construction
there is no evidence of any permanent displacement of prey as a result of operational noise
and therefore no further assessment is required.
Background
7.43 Sandwich terns are specialised foragers and feed almost exclusively on clupeids and sandeels
which are caught near the surface by plunge diving from a height of 5-10m (Stienen et al. 2000,
Stienen and Brenninkmeijer 2002).
Effect of piling on prey species
7.44 Sandeel lack a swim bladder and thus have a lower hearing ability than clupeids (Hawkins
1981). Accordingly, any effect of piling noise on sandeels shall be far more localised. Pre and
post construction surveys undertaken at Horns Rev did not detect any decrease in the density
44
of sandeels present (Jensen et al. 2004). Seismic surveys have been found to have little effect
on sandeels in close proximity to air guns with little or no mortality and only minor avoidance
(Hassel et al. 2004). Consequently there is little evidence to suggest that sandeels would not
remain at or in the vicinity of piling operations.
7.45 During the period from Monday 10th July to Monday 24
th July 2006, Subacoustech Ltd deployed
a team of engineers from Mostyn Dock to undertake measurements of the impact piling noise
during construction of the Burbo Bank Offshore Wind Farm. Burbo Bank used 4.7m diameter
monopiles. In this case, the hearing threshold for herring was cited as 90dBht; consequently the
impact piling operation may have caused a strong behavioural avoidance response in herring to
a range of approximately 2.6km (Parvin and Nedwell 2006). DECC notes that each project in
The Wash may use monopiles of up to 6.5m diameter which require more energy to drive into
the seabed. Centrica (2009) identified a potential physical impact on herring from pile driving
within 2km of the source and possible disturbance within 10-30km. JNCC and Natural England
noted in response to the Draft Appropriate Assessment that it would be more suitable to use
measurements from larger pile installations which have similar bathymetry. Walney 1 wind farm
used 6.5m piles in 20 - 25 meters of water with a uniformly slopping bathymetry of muddy sand.
The 90dbht disturbance for Herring at Walney was 20km (JNCC and Natural England 2011c).
7.46 The disturbance to clupeids is likely be in the form of an avoidance behaviour and it is predicted
that fish will move away from the sound source as has been found for other species (Mueller-
Blenkle 2010). Consequently, any direct physical impact will be localised but there is a
possibility of some displacement. Although there will be inter and intra-seasonal variations the
data indicate that there is a wide foraging range across the Greater Wash area and should
foraging opportunities decrease in an area due to disturbance during construction there are
other locations within the same foraging distance that will be utilised. However, the scale of
effect will be relatively localised compared to the overall foraging area.
7.47 Given the foraging range of Sandwich terns and their seasonal foraging patterns which favour
coastal waters during the summer months (ECON 2011a), it is unlikely that breeding Sandwich
terns would encounter significant differences in the availability of clupeids during piling activity.
Sandeels are unlikely to be displaced by piling activity.
7.48 In response to the Draft Appropriate Assessment JNCC and Natural England (2011c) and the
RSPB (2011) sought clarification that each project would be subject to herring spawning
restrictions to mitigate potential impacts from piling activity during a key period of the herring‟s
lifecycle. Preventing disturbance to spawning herring should ensure that herring recruitment
within The Wash is not adversely affected by the construction of each project and consequently
the prey available to Sandwich terns is maintained over consecutive years.
The following text is a suggested Marine Licence condition to prevent disturbance to spawning
herring. Applicable to Docking Shoal, Race Bank and Dudgeon:
The Licence Holder must ensure that, if construction works are still ongoing, pile
driving activities are not undertaken during the period 1st October to 15th November
in order to prevent disturbance to spawning herring, unless they have written
45
confirmation from the Licensing Authority that based on the assessment of the
outputs of the pre-construction surveys such works are permissible (i.e. that this
condition has been revoked).
Foraging patterns of Sandwich terns
7.49 Centrica commissioned intensive tracking studies of Sandwich terns that have indicated that
Sandwich terns from the North Norfolk Coast SPA forage widely across the Greater Wash area.
Tracking indicates that the foraging range of terns from the SPA is up to 70km, which
corresponds with previous information (BirdLife International 2010) and accords with
information from aerial surveys. Tracking studies indicate that consented and in-development
sites in the Greater Wash are thus within the maximum range of birds from the North Norfolk
Coast SPA; however, terns do not seem to routinely cross Lynn Deeps (a deep water channel)
towards Lynn, Inner Dowsing and Lincs Offshore Wind Farm (ECON 2011a). In general, it
appears that Sandwich terns may be encountered virtually anywhere to the east of the main
channel of The Wash (Lynn Deeps) to the limit of the aerial surveys (around 60km from the
colonies), with possible centres of activity being a south west - north east line along Lynn
Deeps from Hunstanton to Triton Knoll, the north east corner of the Greater Wash at Dudgeon
Shoal and close to the coastline in the late autumn (ECON 2011a).
In combination
7.50 DECC notes that the construction programme for Docking Shoal (Phase 1) (2016 - 17) does not
overlap with piling operations at either Race Bank (2014-16), Dudgeon (2014/15) or Triton Knoll
(~2018/19). Piling activity may overlap at Race Bank and Dudgeon; however, Dudgeon lies
36km to the east of Race Bank.
7.51 DECC notes that monitoring of the Thames herring stock in Herne Bay has been ongoing for
several years due to the construction of Kentish Flats and several other Offshore Wind Farms
in the Thames Estuary. Despite piling activities at Kentish Flats, Gunfleet Sands, Greater
Gabbard and Thanet Offshore Wind Farms, the results have shown neither a noticeable
decrease in herring in the area nor a reduction of spawning activity during piling activity
(CEFAS 2009).
Monitoring
7.52 JNCC and Natural England (2011b) request pre, and post construction monitoring of fish. The
MMO note that such surveys are typically required to contest or confirm herring spawning
restrictions. DECC agrees that the Marine Licence should include the requirement for pre and
post construction monitoring of fish abundance and distribution.
Conclusions
7.53 Taking into account all the above, it is concluded that each project will not cause an adverse
affect on the integrity of the North Norfolk Coast SPA either alone or in combination with other
Offshore Wind Farms, with regard to disturbance of Sandwich terns from foraging sites during
construction.
46
8 OFFSHORE SUB-TIDAL SANDBANKS – ASSESSMENT OF EFFECTS RESULTING FROM
DOCKING SHOAL AND RACE BANK, ALONE AND IN COMBINATION
8.1 Race Bank and Docking Shoal may have a likely significant affect on sandbank features of the
Inner Dowsing, Race Bank and North Ridge cSAC. JNCC and Natural England (2011b)
recommended that DECC considers the following attributes within this assessment:
Extent of sandbank;
Sandbank topography;
Sediment character;
Distribution of sub-features and biotopes; and
Species composition of representative or notable biotopes.
Background
8.2 The Race Bank Offshore Wind Farm coincides partially with the North Ridge, Race Bank and
Dudgeon Shoal sandbank feature which has, since the Race Bank application of January 2009,
become a feature of the Inner Dowsing, Race Bank and North Ridge cSAC. JNCC consulted
upon this cSAC from November 2009 to January 2010.
8.3 Race Bank Offshore Wind Farm is a considerable distance from significant S. spinulosa reef
features of the cSAC and the applicant has committed to avoid S. spinulosa (See Figure 8.1
and the condition suggested in paragraph 4.15). As a result, reef features are scoped out of this
assessment.
Results
8.4 Gravity Based Foundations are assumed to be the worst case option in relation to
coastal/physical processes as they have the largest footprint on the seabed of all the foundation
options and hence the greatest potential effect on coastal processes.
8.5 Extent of sandbank: The analysis in Table 8.1 show that 0.25% of the entire sand bank
feature would be affected with a permanent loss of 0.14% of the entire sandbank feature
(ABPmer 2011). At no point does the loss of the sandbank feature increase above 1% of the
entire cSAC feature.
47
Figure 8.1 Inner Dowsing, Race Bank and North Ridge cSAC and wind farms
(Source ABPmer 2011)
8.6 Sandbank topography: From analysis of historical charts, Race Bank is considered to be a
stable feature, although with mobile sand waves on the seabed (Centrica 2009). The
predominant sediment transport pathway across the cSAC is north-westerly (ABPmer 2011).
The presence of both Race Bank and Docking Shoal could, in combination, create a „channel‟
in which currents are predicted to increase by a maximum of 0.1ms (ABPmer 2011). The
increase in current may increase the mobility of sand sized sediment by 2% but sediments
within the channel are coarse, large particles which are insensitive to changes in flow speeds
(ABPmer 2011). If any change to sediment mobility occurred then it is liable be very minor. Any
reduction in the rate of morphological change, owing to a change in sediment mobility, is
unlikely to be distinguishable from natural variability (ABPmer 2011). The overall transport
pathway remains unchanged so the overall sandbank topography shall be maintained.
8.7 Sediment character: The sandbank is comprised of relatively uniform sands extending to a
depth greater than the expected level of excavation (ABPmer 2011). During construction and
decommissioning, sand would be disturbed which would be rapidly re-deposited on the seabed
and would not cause a significant increase to the background sediment concentrations nor
change the sediment composition or character (Centrica 2009). Scour protection would
introduce new substrate but the extent of change is minor – 0.14% of the sandbank feature.
8.8 Distribution of sub-features and biotopes: Most benthic fauna found on sandbank features
are either sessile or, if motile, will not be able to move sufficiently quickly to avoid being killed
consequently any fauna covered by the turbine base or scour would be lost. There is the
48
potential for a permanent loss of 0.14% sub features and biotopes within the direct foot print of
the wind farm (ABPmer 2011). The impact on biotopes, community composition and the
population structure are considered minor because the Race Bank feature is a highly dynamic
environment in terms of sediment transport. Such sandbanks are typically characterised by
relatively impoverished faunal assemblages consisting of species with a low sensitivity to
physical disturbance (being regularly exposed to harsh physical processes). Such communities
exhibit high recoverability either through migration from nearby areas or through the settlement
of planktonic larvae (ABPmer 2011). The overall distribution of subtidal sandbank communities
would be maintained.
8.9 Species composition of representative or notable biotopes: The community composition
and population structure may experience changes due to the introduction of a hard substrate.
However, the hard substrate would only affect a maximum of 0.14% of the total sandbank area.
Again, DECC considers this change minor.
Conclusion
8.10 Taking into account all the above, it is concluded that the proposed Race Bank Offshore Wind
Farm, will not adversely affect the integrity of the Inner Dowsing, Race Bank and North Ridge
cSAC, either alone or in combination with the other wind farms.
49
Table 8.1 Summary of impacts on Inner Dowsing, Race Bank and North Ridge cSAC (Source ABPmer 2011).
Impact Nature of
impact Scenario used
1
Impact within the Race Bank Sandbank
2
Impact within the Entire cSAC Sandbank feature
Impact within the entire cSAC Area
Proportion of area affected
(%)2
Absolute area
affected (m
2)
Proportion of area affected
(%)3
Absolute area
affected (m
2)
Proportion of area affected
(%)4
Absolute area
affected (m
2)
Direct loss of seabed due to the footprint of the wind turbine bases, substations and associated scour protection
Permanent
96 x 6MW with gravity based foundations and two gravity based substations cover the greatest area of seabed
0.16 299,000 0.14 299,000 0.07 623,400
Disturbance of seabed due to inter-array cabling
Temporary 6MW cable layout with two substations uses the greatest length of cable
0.049 90,800 0.042 90,800 0.028 235,300
Disturbance of seabed due to export cabling
Temporary Two substations layout uses greatest length of cable
0.04 71,600 0.03 71,600 0.01 119,000
Physical disturbance of seabed habitat during installation (use of jack-up rigs)
Temporary
96 x 6MW turbines and two substations requires the largest number of jack-up rig deployments
0.003 5,600 0.003 5,600 0.001 11,800
Total 0.25 467,000 0.25 467,000 0.12 989,600
Total Permanent 0.16 299,000 0.14 299,000 0.07 623,400
Total Temporary 0.09 168,000 0.08 168,000 0.04 366,100
Notes:
1. The scenario used is the worst case with respect to the size of footprint within the total cSAC area (ABPmer 2011)
2. The Race Bank sandbank is a collective term for the Race Bank, West Ridge, North Ridge and Dudgeon Shoal features and covers an area of 95,916,482.59m2 (ABPmer 2011)
3. Draft cSAC area - which reflects changes made to the boundaries as a result of consultation and now measures 218,262,420m2 (JNCC Pers Comm 23/04/2010)
4. Draft cSAC - which reflects potential changes made as a result of consultation using an entire cSAC area of 844,986,205.02m2 (JNCC Pers Comm 23/04/2010)
50
9 INSHORE SUBTIDAL SANDBANKS – ASSESSMENT OF EFFECTS RESULTING FROM
DOCKING SHOAL AND RACE BANK, ALONE AND IN COMBINATION
9.1 The export cables from Docking Shoal and Race Bank may affect the inshore sub tidal
sandbank features of The Wash and North Norfolk Coast SAC. DECC considered the following
attributes within this assessment:
Extent of subtidal sandbank;
Sandbank topography;
Sediment character;
Distribution of biotopes; and
Species composition of representative or notable biotopes.
Background
9.2 In total, a maximum of ten export cables will be laid through The Wash (assuming that all three
s36 applications are consented). Two from Lincs Offshore Wind Farm, four from Docking Shoal
and four from Race Bank. The export cables will be installed using ploughing or jetting
techniques. DECC notes that the first Lincs export cable has been installed using a plough
towed by the cable laying vessel. The cable is simultaneously buried as the cable ship and
cable plough make forward progress (BERR 2008). DECC also notes that the installation
programme for Centrica projects indicates that jetting would be the worst case impact for
installing the eight export cables from Docking Shoal and Race Bank, in relation to immediate
substrate loss on the benthic fauna both within and on the seabed.
Results
9.3 Extent: Subtidal sandbanks are identified as a feature within The Wash and North Norfolk
Coast SAC although the total area of subtidal sandbank habitat has not been described.
Assuming all the main biotopes recorded along the cable route from the site specific surveys
could be classified as subtidal sandbanks then a total of 2.4km2 may be impacted by cable
laying activities if jetting is used. Approximately 1.2km2 would be affected if all cables were
installed by ploughing. The total area of the SAC is 1,077 km2 therefore less than 0.22% of the
SAC may be temporarily impacted from the jetting of the 9 remaining cables and accounting for
the Lincs export cable which has been installed by ploughing (Centrica 2008, 2009).
9.4 DECC notes that Natural England has previously advised that their preferred cable installation
method for Lincs was by ploughing (Natural England 2008). The first export cable for Lincs has
been installed by plough. If the Docking Shoal and Race Bank cables are installed by plough
then the total area impacted is 0.11%.
9.5 Topography: Subtidal sandbanks occur in areas of strong tidal currents and are physically
affected by the strength of currents, wave action and storms (Jennings et al. 1999, Allen 2000).
The nature of the receiving environment within which cable laying activities will take place
51
indicate that the cable track will be rapidly back-filled by subsequent tidal movement and
therefore there will not be anything more than a temporary impact on the topography of subtidal
sandbanks with the immediate start of recovery of the seabed following disturbance (BERR
2008).
9.6 Sediment character: The sediments fluidised would be rapidly re-deposited on the seabed and
would not cause a significant increase to the background sediment concentrations nor change
the sediment composition or character (Centrica 2009).
9.7 Distribution of sub-features and biotopes: Most benthic fauna found on sandbank features
are either sessile or, if motile, will not be able to move sufficiently quickly to avoid being killed
consequently any fauna covered by the base or scour would be lost. The worst case scenario
for a loss would be 0.23% of sub features and biotopes within the direct foot print of the export
cables. The impact on biotopes, community composition and the population structure are
considered minor because the sub-tidal feature is a highly dynamic environment in terms of
sediment transport. Sediment re-suspension frequently results in highly turbid waters (Allen
2000). The nature of the benthic communities reflects these dynamic environmental conditions
with community structure being primarily a function of depth and physical processes. Such
communities exhibit high recoverability either through migration from nearby areas or through
the settlement of planktonic larvae (ABPmer 2011). The overall distribution of subtidal
sandbank communities would be maintained.
9.8 Species composition of representative or notable biotopes: Cable installation shall not
increase the abundance of invasive species nor introduce any new substrate or physical
processes which might change the species composition along the export cable route.
Conclusions
9.9 Taking into account all the above, it is concluded that the Docking Shoal and Race Bank
Offshore Wind Farms, will not cause an adverse effect on the integrity of The Wash and North
Norfolk Coast SAC with regard to inshore subtidal sandbanks, either alone or in combination
with Lincs Offshore Wind Farm.
52
10 INTERTIDAL MUDFLATS AND SANDBANKS – ASSESSMENT OF EFFECTS RESULTING
FROM DOCKING SHOAL AND RACE BANK, ALONE AND IN COMBINATION
10.1 The export cable from Docking Shoal and Race Bank may affect the intertidal mudflats and
sandbank features of The Wash and North Norfolk Coast SAC. DECC considered the following
attributes within this assessment:
Extent of intertidal mudflats and sandbanks;
Sandbank topography;
Sediment character;
Distribution of sub-features and biotopes (notably cockles); and
Species composition of representative or notable biotopes.
Background
10.2 Intertidal mudflats and sandflats are submerged at high tide and exposed at low tide.
10.3 Centrica shall install up to 10 export cables through The Wash and Norfolk Coast SAC: two
export cables for the Lincs project (of which one has already been installed) and eight export
cables for both Race Bank and Docking Shoal (Centrica 2007, 2008, 2009).
Results
10.4 Extent: The extent of the impact of jetting for the 9 cables, in combination, would be
approximately 0.25km2 out of a SAC area of 1,077km
2, of which 183km
2 is classified as inter-
tidal. Therefore approximately 0.14% of the intertidal habitat would be impacted if jetting were
used to install the export cables for Lincs, Race Bank and Docking Shoal (Centrica 2007,
2008).
10.5 The extent of the impact of ploughing is approximately 0.12km2. Therefore approximately
0.07% of the intertidal habitat will be impacted by installing the maximum of 10 export cables by
plough (Centrica 2007, 2008).
10.6 Topography: The nature of the receiving environment within which cable laying activities will
take place indicate that the cable track will be rapidly back-filled by subsequent tidal movement
and therefore there will not be anything more than a temporary impact on the topography of
intertidal sandbanks. Dare et al. (2004) note that visible hydraulic suction dredging tracks
persist for a few days or weeks in The Wash according to the tidal and wave conditions
however it should be noted that a plough is designed to replace the sediment in situ whilst a
dredge removes sediment. Any changes to topography shall be temporary and shall not affect
the integrity of the intertidal sandbanks and mudflats.
10.7 Sediment character: The sediments fluidised would be rapidly re-deposited on the seabed and
would not cause a significant increase to the background sediment concentrations nor change
the sediment composition or character (Centrica 2009).
53
10.8 Distribution and extent of characteristics biotopes: Most benthic fauna found on intertidal
mudflats and sandbank features are either sessile or, if motile, will not be able to move
sufficiently quickly to avoid being killed consequently any fauna covered by cable laying would
be lost. Adopting the worst case; there shall be a loss of 0.13% of sub features and biotopes
within the direct foot print of the export cables, should all remaining nine (9) export cables for
the Lincs, Race Bank and Docking Shoal projects be installed by jetting. The impact on
biotopes, community composition and the population structure are considered minor because
the intertidal sandbanks feature is a highly dynamic environment in terms of sediment transport.
Sediment re-suspension is frequent resulting in highly turbid waters (Allen 2000).
Cockles – attribute of the intertidal mudflat and sandbank feature
10.9 JNCC and Natural England (2011b) raised concern that cabling through commercial cockle
beds may affect the food resource available for features of The Wash SPA. The following
sections (10.10 to 10.22) consider impacts on the features and attributes of The Wash and
North Norfolk Coast SAC and where relevant should also be read as an assessment of the
impact on those features of The Wash SPA that rely on these as a food resource.
10.10 The export cable route runs through the edge of the extensive intertidal cockle beds and close
to the intertidal mussel beds, both of which are of commercial and conservation importance.
The indicative cable route may pass through an aggregation of fishable cockles close to the
eastern bank of the River Nene. However, the cable route has been altered so that it only
passes through the outer edge of the cockle bed.
10.11 The Marine Licence will contain a condition requiring the submission of a Cockle Bed Mitigation
Plan. This shall require Centrica to survey the cockle beds, prior to cable installation, and
submit a plan to mitigate any impact to the cockle beds of the proposed works, where
necessary. Mitigation may include, dredging and reseeding cockles in impacted areas of the
beds, the use of low pressure vehicles for the cable installation works and the restriction of
cable works to a very narrow corridor within the cockle beds. This plan will need to be reviewed
by the MMO in consultation with Natural England and the Eastern Inshore Fisheries and
Conservation Authority (EIFCA) prior to any cable works commencing. The MMO has advised
that this Plan should incorporate lessons learnt from the installation of the Lincs OWF export
cable lay (MMO, Pers comm., 24 April 2012)
10.12 The Wash Cockle Fishery is regulated by EIFCA. In May 2011, further cockle data were
received from the EIFCA showing the results of their latest surveys within The Wash. For
comparison, these were mapped against the cockle distribution presented in the Docking Shoal
and Race Bank Environmental Statements and against the revised export cable corridor. In
general, the extent of cockle beds within The Wash has decreased, with the EIFCA‟s
appropriate assessment under Regulation 61 of The Conservation of Habitats and Species
Regulations 2010 concluding that no further suction dredging should take place in The Wash
over the 2011/12 season. EIFCA (2011b) noted in their response to the draft AA that this does
not preclude suction dredging in subsequent years which may coincide with cabling.
54
10.13 EIFCA opened all but two cockle beds in The Wash for hand working in June over the 2011/12
season (EIFCA 2011b). The Inner Westmark Knock cockle bed remains open for hand working
(EIFCA 2011b). DECC notes that, whilst installing the Lincs export cable, Centrica has worked
alongside the EIFCA and cockle fishermen to reach an agreement which maintains the cockle
fishery in The Wash. This agreement includes extensive pre- and post cable installation
monitoring of the commercial cockle beds.
10.14 The effects of cable laying on fishing grounds would be temporary and localised. Cable vessel
burial rates mean that disruption to cockle beds would be minimal. The area of cockle bed
affected by cable installation of the Lincs, Race Bank and Docking Shoal export cables was
determined to be 0.25km2, or 0.25% of the total available resource which includes both
commercial and natural cockle beds (Centrica 2011a, 2011b). Centrica intends to meet with
EIFCA to discuss ways of clarifying the available cockle beds further reducing any impacts.
10.15 With regards to effect that the temporary loss of cockles may have on The Wash SPA features:
EIFCA (2011a) state that “in reality, the conservation objective relating to cockle and mussel
stocks is likely to be well exceeded because private mussel lays in The Wash are well-stocked
(rough estimates show around 10,000 tonnes mussel are currently held within the Several
fishery). These stocks are not included in estimates because there is no management control
on these stocks – however, layholders have stated that even with a fishery occurring on the
lays, significant quantities of mussels will be left in situ because they are too small to be fished
this year. Cockle and mussel stocks also exist in the private Le Strange Estate area of The
Wash; these stocks are not counted because they do not fall within EIFCA management, but
again they will contribute to food stocks for the relevant SPA species.” Furthermore The Wash
is the second largest area of intertidal flats in the UK with 30,700ha of intertidal mudflats and
sandbanks which are rich in invertebrate and provide extensive feeding for waders and wildfowl
(Schofield et al. 1992). The extent and duration of any change is unlikely to deplete the
biomass of the large intertidal area so there shall be no significant effect on wintering, passage
and breeding birds.
10.16 Cable installation may increase sediment loads within the cockle beds. Plume Dispersion
Modelling predicts resulting sediment loads, settling rates and plumes during installation of the
export cables through standard marine jetting (as a worst case scenario). The model predicts
sediment loads and deposition thickness at the intertidal mussel and cockle beds to the south-
east of the proposed export cable corridor. The results found that suspended sediment
concentrations at the mussel and cockle beds would be 0.48mgl-1 and 0.24mgl-1 respectively,
ten days after release, and that sediment deposition thickness would be less than 0.1mm
(Centrica 2008, 2009). The Marlin database (www.marlin.ac.uk) states that, for this habitat,
smothering of up to 5cm is unlikely to affect deposit or suspension feeders, particularly when
the smothering sediment was typical of the area. DECC notes that the cockle beds are subject
to a ‘prop- wash’ from fishermen whereby the vessel is manoeuvred around above the cockles
55
to remove sediment prior to harvesting. The impacts of prop-washing were found not to cause
significant adverse effects to the cockle population or the supporting habitat (EIFCA 2011a).
10.17 DECC notes that cockles have behavioural adaptations to disturbance in response to the
dynamic nature of their environment. They are active burrowers and have the ability to rapidly
rebury after exposure. Hand raking of cockles has been demonstrated to have no effect on the
ability of cockles to rebury (McLaughlin et al. 2007) and even after mechanical harvesting
cockles are able to rebury to survive (Cook 1988, Coffen-Smout and Rees 1999).
10.18 Species composition: Potential impacts to the inter-tidal habitats will be through physical
disturbance or indirect impacts on benthic communities arising from smothering and reduction
in water quality. Intertidal mudflats and sandflats are areas of very high sediment transportation
and deposition and any physical impact will be of short duration with tidal currents rapidly
causing the infilling of any areas of impact.
10.19 Intertidal species that occur in mudflats and sandbanks in The Wash areas are equipped to
cope in environments with high sediment loads and the increase in suspended sediment arising
from cable laying are not thought to cause changes in the communities present (CEFAS 2001).
Any impacts that may occur shall be localised and temporary with the short lived species
impacted being able to rapidly re-colonise areas of disturbance with longer lived species re-
colonising over time.
10.20 Owing to mobility of sediment and consequent abrasion, species that inhabit clean sands tend
to be mobile and robust and include amphipod crustaceans, such as sandhoppers Bathyporeia
spp., some polychaete worms and bivalve molluscs (English Nature 2000). None of the
biotopes identified at the receptor sites are sensitive to increased suspended sediment loads
and are of only low sensitivity to sediment deposition. This is not surprising given the
occurrence of these biotopes in conditions where proximity to mobile sediments is normal. The
overall distribution and extent of characteristic biotopes would be maintained.
10.21 DECC notes that one export cable from the Lincs project has already been installed, by plough,
through The Wash. The construction programme for each project dictates that there will be a
gap of at least a year or more between cable installation between Lincs, Race Bank and
Docking Shoal.
Conclusions
10.22 Taking into account all the above, it is concluded that the proposed Docking Shoal and Race
Bank Offshore Wind Farms, will not cause an adverse effect on the integrity of The Wash and
North Norfolk Coast SAC with regard to intertidal mudflats and sandbanks, either alone or in
combination with Lincs cabling through The Wash and North Norfolk Coast SAC.
56
11 DECOMMISSIONING
11.1 Each project falls within the scope of the Energy Act 2004 which includes decommissioning
provisions. Broadly speaking, the Secretary of State shall require a person who is responsible
for an offshore renewable energy installation to prepare a costed decommissioning programme
and ensure that it is carried out. The Secretary of State can approve, modify or reject a
decommissioning programme.
11.2 Decommissioning activities will need to comply with all relevant UK legislation at the time. Such
legislation currently includes The Conservation of Habitats and Species Regulations 2010 (as
amended) and the Offshore Marine Conservation (Natural Habitats, &c.) Regulations 2007 (as
amended). The person(s) responsible for the wind farm will produce and agree a
decommissioning programme with DECC and in consultation with the MMO, JNCC and Natural
England, or their respective successors.
11.3 Decommissioning will take place at the end of the lifetime of each wind farm. All of the wind
turbines and substations (including foundations) will be removed. There is potential for the wind
farm to be re-powered.
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12 CONCLUSIONS IN RELATION TO EFFECTS ON THE INTEGRITY OF EUROPEAN SITES
12.1 Based on environmental information relating to the Docking Shoal (Phase I), Race Bank and
Dudgeon Offshore Wind Farms and supported by published data from other sites, it is
concluded that sufficient information is available to enable an Appropriate Assessment to be
made both alone and in combination with other plans and projects.
Harbour seals – The Wash and North Norfolk Coast SAC
12.2 The Secretary of State does not consider that the construction of Docking Shoal (limited to a
100MW Phase I), Race Bank and Dudgeon Offshore Wind Farms shall adversely affect the
integrity of Harbour seals in The Wash and North Norfolk SAC, for the following reasons:
Each project shall agree a Marine Mammal Mitigation Protocol with the MMO, in
consultation with JNCC and Natural England, prior to consent;
Piling noise from each project shall not displace nursing Harbour seals from inshore
waters at Blakeney Point;
Mature Harbour seals are opportunistic foragers who forage across The Wash and
beyond; and
Piling simultaneously at Race Bank and Dudgeon shall not create a barrier to Harbour
seal movement nor displace a significant number of Harbour seals from foraging areas.
The Secretary of State notes that any Marine Licence (issued by the MMO) will require
monitoring of underwater noise levels during piling operations.
Sandwich terns - North Norfolk Coast SPA
12.3 The Secretary of State does not consider that the construction and operation of Docking Shoal
(Phase 1), Race Bank and Dudgeon Offshore Wind Farms shall adversely affect the integrity of
the breeding population of Sandwich terns from the North Norfolk Coast SPA, for the following
reasons:
Each project can be modified, within the Rochdale Envelope, to reduce impact on
Sandwich terns;
The predicted annual mortality, both alone and in combination with Sheringham Shoal
and Triton Knoll Offshore Wind Farms does not exceed 94 individuals when using an
avoidance rate of 98.83% provided that the installed capacity at Docking Shoal (Phase
1), Race Bank, Dudgeon and Triton Knoll is reduced.
Sandwich terns have extensive foraging ranges and adult birds provisioning chicks
favour coastal waters during the summer months. Sandeels are unlikely to be displaced
over a significant distance from piling. Clupeids may be displaced from the waters but
58
the overall prey availability shall not change and will remain well within the foraging
range of Sandwich terns.
Alternatively, the application for a scheme at Docking Shoal can be refused and the predicted
Sandwich tern mortality associated with this scheme can be reallocated to the Race Bank,
Dudgeon, and (without prejudice to its consideration by the Planning Inspectorate) Triton Knoll
schemes such that a restriction on the number of turbines (within the maximum capacity of the
site) is not required.
Offshore subtidal sandbanks – Inner Dowsing, Race Bank and North Ridge cSAC
12.4 The Secretary of State does not consider that the construction and operation of Race Bank
Offshore Wind Farm will adversely affect the integrity of the Inner Dowsing, Race Bank and
North Ridge cSAC with regard to sub-tidal sandbanks, either alone or in combination with
Docking Shoal, for the following reasons:
At no point does the extent of the potential loss of the subtidal sandbank feature
increase above 1%;
The sandbank topography and character shall be maintained; and
The distribution of sub-features and biotopes will be maintained.
Inshore subtidal sandbanks - The Wash and North Norfolk Coast SAC
12.5 The Secretary of State does not consider that the installation of export cables from the Docking
Shoal offshore wind farm (if consented) and the Race Bank offshore wind farm will adversely
affect the integrity of The Wash and North Norfolk Coast SAC with regard to sub-tidal
sandbanks, either alone or in combination with Lincs Offshore Wind Farm, for the following
reasons:
At no point does the extent of the potential loss of the inshore subtidal sandbank
feature increase above 1%;
The inshore subtidal sandbank topography and character shall be maintained; and
Any loss of sub-features and biotopes will be small in extent and temporary owing to
the high recoverability within what is already a highly dynamic environment.
Intertidal mudflats and sandbanks - The Wash and North Norfolk Coast SAC
12.6 The Secretary of State does not consider that the installation of export cables from the Docking
Shoal offshore wind farm (if consented) and the Race Bank offshore wind farm will adversely
affect the integrity of The Wash and North Norfolk Coast SAC with regard to intertidal mudflats
and sandbanks, either alone or in combination with Lincs Offshore Wind Farm, for the following
reasons:
At no point does the extent of the potential loss of intertidal mudflats and sandbanks
increase above 1%;
59
The total impact on cockle bed will be localised, temporary and only 0.25% of the total
resource;
The topography and character of the intertidal mudflats and sandbanks shall be
maintained; and
The Wash is the second largest area of intertidal flats in the UK with 30,700ha of
intertidal mudflats and sandbanks which are rich in invertebrate and provide extensive
alternative feeding for waders and wildfowl.
Summary
12.7 The Secretary of State concludes that the Race Bank and Dudgeon offshore wind farms shall
not have an adverse effect on the integrity of the following European Sites, either alone or in-
combination with other plans or projects:
The Wash and North Norfolk Coast Special Area of Conservation (SAC);
The Inner Dowsing, Race Bank and North Ridge candidate Special Area of
Conservation (cSAC); and
The North Norfolk Coast Special Protection Area (SPA) - provided that the Docking
Shoal scheme is refused such that the predicted annual Sandwich tern mortality
(including the predicted impact from the Triton Knoll and Sheringham Shoal offshore
wind farms) falls within a 94 bird limit.
12.8 The Secretary of State additionally notes that Docking Shoal (Phase 1), Race Bank Offshore
Wind Farm and Dudgeon Offshore Wind Farm shall not have an adverse effect on the integrity
of the following European sites, either alone or in combination with other plans or projects:
The Wash and North Norfolk Coast Special Area of Conservation (SAC);
The Inner Dowsing, Race Bank and North Ridge candidate Special Area of
Conservation (cSAC); and
The North Norfolk Coast Special Protection Area (SPA) - provided that the capacity at
Docking Shoal (Phase 1), Race Bank, Dudgeon and Triton Knoll is restricted such that
the predicted annual Sandwich tern mortality (including the predicted impact from Triton
Knoll and Sheringham Shoal offshore wind farms) falls within a 94 bird limit.
12.9 The Secretary of State notes that the implementation of Marine Licence conditions on the
timing of intertidal working in The Wash and seasonal restrictions on piling activity to avoid
impacts on herring spawning will further reduce the risk of any potential adverse effects.
Author National Infrastructure Consents Team, Energy Development Unit, DECC
Date December 2011, updated June 201221
21
Text amended, 16 July 2012, to remove details of turbine manufacturer
60
APPENDIX 1: SUMMARY OF RESPONSES TO DRAFT APPROPRIATE ASSESSMENT ISSUED FOR COMMENT 30th
September 2011
Organisation Summary of response Amendments
Marine Management Organisation
Confident that the conclusions of the Appropriate Assessment are supported with sufficient evidence and the mitigation proposed within the assessment is appropriate to support the conclusion that Docking Shoal Phase 1, Race Bank and Dudgeon Offshore Wind Farms will not have an adverse effect on the integrity of European Sites, either alone or in combination. Shall not provide a response on the effects of Sandwich terns until the MMO has appointed consultants.
None.
The MMO have commissioned an independent review of the Folkerts model. The preliminary results suggest the Folkerts model provides a realistic and reasonable model to inform this assessment. The outcomes of the MMO‟s ornithological review will feed into the decision-making process prior to determination.
The SPA review was conducted in 2001, is there a more up to date figure that could be used for the assessment?
None. The SPA citation figure is used.
It is acknowledged that seals are likely to be displaced in some instances during the construction phase, it is imperative that this does not occur during periods where mothers are giving birth to young.
None. Harbour seals give birth to their young on land or in very shallow water; neither location would be exposed to significant levels of piling noise. See section titled: Effects of piling noise on foraging behaviour of nursing Harbour seals.
The use of the dBht metric throughout is not ideal as this method has yet to be published in peer reviewed scientific literature.
None. dBht is a valid measure of the behavioural and auditory effects of underwater noise. See: http://www.subacoustech.com/information/downloads/reports/534R1231.pdf
JNCC and Natural England
Suggest that it is not possible to consider 98.83% as a definitive avoidance rate across The Wash.
None. The field study of tern collisions with wind turbines at Zeebrugge provides the best empirical evidence available on the avoidance rates of terns.
Consider that DECC has not provided a detailed examination of the risk associated with using a higher level of mortality.
See Section 7.
Question the validity of the Collision Risk Modelling DECC has amended the Collision Risk Modelling to reflect the
61
Organisation Summary of response Amendments
Methodology. Namely:
The method used to calculate flight density;
The method used to account for non-SPA birds; and
The use of the Folkerts collision risk model.
survey methods used at each site. DECC has not sought to alter the correction factor attributed to non-SPA birds as JNCC/NE noted that, for these projects, the result would have little or no effect on the mortality figures (JNCC/NE 2011d). DECC notes JNCC/NE‟s position regarding the use of the Folkerts model but intend to use this model as it is assumed to represent the offshore environment and conditions more accurately than the Band model.
DECC should undertake a population level risk assessment of Harbour seals in The Wash.
None. DECC and the MMO are satisfied that the MMMP, piling schedule, herring spawning restrictions and relative usage of each site provide sufficient evidence to conclude the AA.
Centrica must carry out detailed ground investigation and provide evidence of how previous issues have been overcome otherwise alternative methods or landfall sites should be assessed.
There are engineering options other than HDD which have the potential to cross the salt marshes by non-open cut methods (See Section 4). The Marine Licence shall include a condition to ensure the salt marsh is crossed by non-open cut methods.
There is no information in the AA which demonstrates that micro-siting round S. Spinulosa is feasible.
DECC notes that there is sufficient room to micro-site within the indicative cable corridor and the wind farms themselves, as required by condition of the Marine Licence (see Section 4 – Sabellaria spinulosa reef).
Impacts on the commercial cockle bed and The Wash SPA should be assessed
The effects on the cockle beds have been updated and works through The Wash shall avoid the overwintering season.
EIFCA No consideration of the effects of The Wash SPA designation.
The effects on the cockle beds have been updated and works through The Wash shall avoid the overwintering season.
Expect a clear justification of the decision to scope out effects on S. Spinulosa Annex I Reef Habitat and how micro-siting of the cable (to avoid areas of core Annex I reef) would be managed.
DECC notes that there is sufficient room to micro site within the indicative cable corridor and the wind farms themselves, as required by condition of the Marine Licence (see Section 4 – Sabellaria spinulosa reef).
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Organisation Summary of response Amendments
Intertidal sand and mud features: No consideration of the wider footprint and effect of cabling operation (i.e. anchoring, vessels laying on etc).
Section 10 deals with vessel anchoring and movement through commercial Cockle Beds
Intertidal sand and mud features: No consideration of in-combination effects, specifically with fisheries both with respect to SAC intertidal and SPA species
None. The impact of cable installation is not consider a likely significant effect either alone or in combination.
Intertidal sand and mud features: AA should factor in some variability and consider effects in this context rather than based on the most recent figures.
None. The assessment is made using the available evidence and incorporates precaution as necessary.
RSPB RSPB response is focussed on potential ornithological impacts only. Welcome the view that it is necessary for mitigation to be adopted for all three projects. RSPB agrees, in principle, to the concept of a Grampian Condition for Docking Shoal.
None.
Provide justification for use of a mortality threshold greater than 75, i.e. that recommended by Natural England and JNCC
See Section 7
Use predicted collision risk figures for all projects that do not exclude a proportion of individuals on the basis of adjustment for passage birds, given the associated uncertainty
See Section 7
Use the most appropriate predicted collision risk figures for all projects and present a clear, stepwise explanation of how the final figures have been derived, with justification for each step, and explanation of why the adopted approach is most applicable
See Section 7
The AA assesses only the potential impact of increased None. Piling will be subject to restrictions to avoid herring
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Organisation Summary of response Amendments
energy expenditure by Sandwich terns as a result of populations of sensitive prey species being displaced from the sites during piling activity.
There is no assessment of the potential (longer term) impact of overall reduction in prey stocks as a result of lethal effects on earlier life stages and/or disruption of spawning activity over several successive (potentially overlapping) years of piling activity, should piling coincide with sensitive periods.
spawning periods.
Lincolnshire Wildlife Trust
If DP vessels are being used; all four points in paragraph 4.10 should therefore be adopted into the Marine Mammal Mitigation Protocol (MMMP). The MMMP should go a step further than this and should halt, subject to navigational safety, the operation of the ducted propellers if a seal is seen within the vicinity of the vessel and therefore potentially at risk from injury.
None. A detailed MMMP must be agreed with the MMO in consultation with JNCC and Natural England, prior to construction, based on the latest inter-agency protocol (JNCC 2010). This shall be a condition of any Marine Licence.
Wish to be assured that any S. spinulosa reefs present in the development area will be protected and that micro-siting can be implemented successfully to avoid any reef features. LWT drew DECC‟s attention to potential S. spinulosa reefs identified as part of the MCZ process.
Noted. The Marine Licence will have a condition requiring the developers to conduct an Annex 1 habitat survey prior to construction so that all turbines cables etc can be micro sited around any interest features.
A condition of consent should be included that ensures no projects pile simultaneously.
Race Bank and Docking Shoal shall not pile simultaneously. The distance (36km) and relative importance of Dudgeon (based on survey data) suggests that their shall be no adverse effect on Harbour seals from The Wash and North Norfolk Coast SAC.
Pre, during and post-construction monitoring should be carried out for sandeels and herring. This would allow the herring spawning season to be avoided.
None. Pre and post construction monitoring for sandeels and clupeids shall be a condition of any Marine Licence.
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Organisation Summary of response Amendments
The Lincolnshire Wildlife Trust would advise that the export cables be laid by plough rather than jetting to minimise the area impacted by installation.
None. The assessment considers the worst case scenario. DECC notes that the first Lincs export cable has been installed by plough through the subtidal area.
Paragraphs 10.6 and 10.8 – These paragraphs refer to subtidal features but it is in the intertidal sandbank feature section.
Corrected.
Centrica Concerns regarding the mitigation proposed with respect to Harbour seal and believe that recent discussions within the offshore industries have highlighted the fact that the cause of these incidents are unlikely to be related to the construction of Offshore Wind Farms.
None. DECC acknowledges in paragraph 4.10 that the use of DP vessels extends beyond offshore wind vessels.
Concerned that the avoidance rate applied for Sandwich tern too precautionary and is not representative of the situation offshore.
None. The field study of tern collisions with wind turbines at Zeebrugge provides the best empirical evidence available on the avoidance rates of terns.
The inclusion of Triton Knoll Offshore Wind Farm has made this appropriate assessment robust.
None.
Dudgeon Offshore Wind Ltd
Sandwich tern avoidance rate remains overly precautionary. A 99% avoidance rate should be used.
None. The field study of tern collisions with wind turbines at Zeebrugge provides the best empirical evidence available on the avoidance rates of terns.
Triton Knoll should not be considered in combination because the application is not yet in the planning system.
None. Triton Knoll is (according to the IPC (now National Infrastructure Directorate) list of projects) liable to enter the planning system before any project, subject to this assessment, are determined. It is thus prudent to consider the effect of Triton Knoll in combination.
Note that Triton Knoll escapes any mitigation. None. The IPC (now National Infrastructure Directorate) and the MMO may choose to apply further restrictions to Triton Knoll
65
Organisation Summary of response Amendments
project at the appropriate time.
Refute the restriction on the number of 3MW turbines permitted.
None. Restriction on turbines used across all three projects are intended to protect the integrity of the Sandwich tern colony.
Seek clarification that Offshore Wind Farm operators are not being disproportionately penalised for corkscrew seal deaths in light of broad use of DP vessels offshore.
None. DECC acknowledges in paragraph 4.10 that the use of DP vessels extends beyond offshore wind vessels.
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APPENDIX 2: SUMMARY OF RESPONSES TO FINAL APPROPRIATE ASSESSMENT ISSUED FOR COMMENT 21th
December 2011
Organisation Summary of response Amendments
Marine Management Organisation
Response received 2nd
march 2012.
MMO response includes comments received from Cefas and a technical review of bird collision risk and prey displacement commissioned by MMO from CEH.
Section 6.15. MMO notes that seals with dependent young will require to forage in areas close to their young (and cannot move away to follow fish prey displaced by piling noise)
Section 6.17. The MMO notes that there is some evidence that acoustic deterrent devices used with fishing nets may attract some seals and consequently any use of these devices within the MMMP would need to be carefully considered and approved by the MMO.
Table 4.1 includes reference to “sub-tidal mudflats” as a European site interest feature scoped into this assessment but not subsequently included in the assessment text.
Having considered the report from CEH the MMO is satisfied with the conclusions of the AA with regard to impacts on Sandwich terns of the North Norfolk Coast SPA subject to the clarification and resolution of the issues raised by CEH regarding standard errors on survival rates (used as input parameters to the PVA model)
The MMO considers that the mitigations proposed within the assessment are appropriate to support the conclusion of no adverse effect on European marine sites
None. Table 6.1 and section 6.12 assess the impact on nursing Harbour seals at Blakeney Point
Text added to section 6.17 to reflect this.
Noted. Table 4.1 amended to correctly describe the interest features as “offshore sandbanks” and “sub-tidal sandbanks” (See section 5.5 and 5.6)
Noted. DECC understands (MMO, pers comm., 26th April 2012)
that further dialogue has occurred between Centrica and CEH and that CEH has advised MMO that its queries have now been satisfactorily addressed
Noted
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Organisation Summary of response Amendments
JNCC and Natural England
Query the use of the Folkerts model citing a discrepancy of between 17.2 and 48.3% when compared with the Band model.
None. The final AA acknowledges that different models will produce different results. An independent review of the Folkerts model concluded that the model is “scientifically robust” (CEH 2012).
CEH (2012) added “The majority of comparisons appear close to or less than 20%. This is encouraging given the inexact nature of these calculations, and given that 20% is the recommended error of uncertainty proposed by Band. With no clear certainty which of the two approaches is closer to the true value, nor that one is unequivocally more robust than the other, we believe that the Folkerts model can be employed where the two estimates are consistently within 20% or less of one another.
CEH (2012) note there is one large anomaly (48.3%) with respect to the collision risk estimates for Docking Shoal. Even with the corrections to the input parameters provided by Centrica, this anomaly still holds. Without the detailed workings of both approaches it is not possible to ascertain whether there is a difficulty with the Folkerts model or with the Band model. Thus, CEH (2012) believe that there is no clear answer to which of the two is closer to the true answer from the information provided. Until someone is able to undertake a comprehensive comparison of the two methods, this anomaly remains unexplained and should not be used to suggest that either model is not scientifically robust. As such, we do not believe that the anomaly provides sufficient evidence to discount the Folkerts model from use in this case.
JNCC/NE note that although an avoidance rate of 98.83% was within a range of appropriate estimates of the mean avoidance rate that could be derived from Sandwich tern from the Zeebrugge wind farm, this did not constitute a recommendation that this was the definitive value to use.
None. The Zeebrugge data represents the “best available scientific evidence” regarding the avoidance of Sandwich terns at a wind farm. Consequently DECC believes this avoidance rate is the best to use for this Assessment. DECC may use a different avoidance rate if the evidence base changes.
JNCC/NE reiterate their advice that a harvest of 75 terns per annum should be viewed as being an upper acceptable limit.
None. DECC maintains the view that 94 is an acceptable upper level of mortality to the Sandwich tern population for the reasons set out in Section 7 of this report, namely:
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Organisation Summary of response Amendments
With no data on emigration / immigration rates it is not possible to conclude if modelling a closed population is precautionary
We do not consider the Dutch work to be further justification for a threshold of 94 birds; in fact it suggests a lower threshold than the 75 advised as the upper threshold of acceptable mortality.
94 represents the absolute risk;
There is precaution within the Population Viability Analysis; and
There is precaution within the Collision Risk Modelling.
DECC acknowledges the absence of reliable data on immigration/emigration rates and has amended the text accordingly
Comment noted and text removed (section 7.20).
JNCC/NE are of the view that the MMMP, piling schedule, herring spawning restrictions and relative usage of the site does not justify the conclusion of no adverse effect.
None. JNCC/NE cite the conclusion of the Section 6 of the AA which is the judgement reached after the detailed deliberation set out in the preceding paragraphs.
To reiterate, the MMMP provides a clear mechanism to avoid near field injury to Harbour seals. The piling schedule means that only two of the four projects are likely to pile at the same time thus limiting the scope of in combination effects. The herring spawning restrictions shall ensure that herring stocks are available as a prey source for harbour seals.
JNCC/NE are of the view that the AA should not focus (just) on the effects on the seals from a single colony at Blakeney Point.
None. Blakeney Point is the closest colony (between the wind farms and piling noise) this represents the “worst case scenario” for the purpose of this AA.
Agree that the saltmarsh features of the North Norfolk Coast SAC shall be protected if HDD techniques or micro tunnelling techniques are used and successful.
None. See section 4.18 which states that crossing the salt marsh by non-open cut methods such as HDD or micro-tunnelling shall be a condition of any consent for Docking Shoal and Race Bank hence DECC scoped these features out of the AA.
Agree that the evidence shows there is sufficient space to micro route the cable around Annex 1 Sabellaria spinulosa reef.
None.
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Organisation Summary of response Amendments
Re-iterate that the cockle stocks have declined but note that the cockle beds could be re-seeded by hand.
Noted. Any cockle bed re-seeding would be agreed, as part of a wider Cockle Bed Mitigation Plan in consultation with the EIFCA and CEFAS. See Section 10.
Passage and overwintering birds could be affected by sequential disturbance or a reduction in food resource due to works in the intertidal.
None. As stated in paragraph 4.19, the Marine Licence shall include a condition as requested by Natural England to restrict works in the intertidal area to the period 01 May and 31 August in any given year to avoid disturbance to overwintering birds and minimise disturbance to passage birds.
The potential impact on food resource for passage and over-wintering birds is assessed at 10.18 to 10.21 (benthic species composition) and 10.9 to 10.17 (cockle stocks).
EIFCA None. None.
RSPB A harvest of 75 terns per annum should be viewed as being an upper acceptable limit.
None. DECC maintains the view that 94 is an acceptable upper level of mortality to the Sandwich tern population for the reasons set out in Section 7 of this report, namely:
94 represents the absolute risk;
There is precaution within the Population Viability Analysis; and
There is precaution within the Collision Risk Modelling.
A single data set from Zeebrugge necessitates the application of precaution.
None. The Zeebrugge data represents the “best available scientific evidence” regarding the avoidance of Sandwich terns at a wind farm. Consequently DECC believes this avoidance rate is the best to use for this Assessment. DECC may use a different avoidance rate if the evidence base changes.
The potential impacts on other SPAs should be considered.
None. JNCC/NE (2010) have scoped their advice to DECC on the North Norfolk Coast SPA.
Concerned that “In the absence of any other information, all surveys from 2004 onwards at Docking Shoal, Race Bank and Dudgeon are assumed to have used the alternative radial survey method. “
None. This assumption takes a precautionary approach i.e. all surveys post 2004 were assumed to exhibit the worst-case in terms of bird density and thus a higher collision risk.
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Organisation Summary of response Amendments
Concerned with the use of the Folkerts model citing a discrepancy of between 40.9 and 48.3% in one scenario at Docking Shoal when compared with the Band model.
None. The final AA acknowledges that different models will produce different results. An independent review of the Folkerts model concluded that the model is “scientifically robust” (CEH 2012).
CEH (2012) added “The majority of comparisons appear close to or less than 20%. This is encouraging given the inexact nature of these calculations, and given that 20% is the recommended error of uncertainty proposed by Band. With no clear certainty which of the two approaches is closer to the true value, nor that one is unequivocally more robust than the other, we believe that the Folkerts model can be employed where the two estimates are consistently within 20% or less of one another.”
CEH (2012) note there is one large anomaly (48.3%) with respect to the collision risk estimates for Docking Shoal. Even with the corrections to the input parameters provided by Centrica, this anomaly still holds. Without the detailed workings of both approaches it is not possible to ascertain whether there is a difficulty with the Folkerts model or with the Band model. Thus, CEH (2012) believe that there is no clear answer to which of the two is closer to the true answer from the information provided. Until someone is able to undertake a comprehensive comparison of the two methods, this anomaly remains unexplained and should not be used to suggest that either model is not scientifically robust. As such, we do not believe that the anomaly provides sufficient evidence to discount the Folkerts model from use in this case.
Agree that the Triton Knoll should be considered as the application is “reasonably foreseeable”. RSPB suggest that the assessment of in combination effects would be clearly lacking if the Triton Knoll application were ignored.
None.
Cannot agree with the conclusion of no adverse effect regarding the indirect effects on Sandwich terns.
None. DECC and the MMO have set out draft conditions applicable to each consent to mitigate and manage the effects of piling noise on clupeids.
Concerned that alternatives to crossing the saltmarsh None. JNCC/NE agree that the saltmarsh features of the North
71
Organisation Summary of response Amendments
feature have not been assessed. Norfolk Coast SAC shall be protected if HDD techniques or micro tunnelling techniques are used and successful.
Cannot agree with the conclusion of no adverse effect regarding the potential impact on cockle beds and indirect effects on wading birds.
None. JNCC/NE note that the cockle beds could be re-seeded by hand.
Centrica Believes that the use of the 98.83% avoidance rate within the Southern Wash AA remains highly precautionary and is inconsistent with the 99.6% avoidance rate used by DECC for the Sheringham Shoal AA.
None. DECC as the competent authority takes the view that the Zeebrugge data represents the “best available scientific evidence” regarding the avoidance of Sandwich terns at a wind farm. DECC may apply a different avoidance rate in future if new evidence emerges.
Centrica notes that the collision rate used for Sheringham Shoal has been increased by 20% from 11 to 13 birds in the Southern Wash AA under the assumption that the surveys carried out for the original Environmental Statement will have utilised radial survey methods (0.141km
2 survey area) but that calculations will have been
on an assumption of the „box‟ survey area (0.18km2 survey
area) and Sandwich tern densities may therefore have been underestimated. It is Centrica‟s opinion that this collision rate increase makes the assessment of collision effects more robust in the Southern Wash AA.
None. DECC has followed a precautionary approach.
Matters relating to the use of ducted propeller vessels are currently being resolved at an industry level through the use of risk-based assessments and Centrica anticipates that the outcome of this work will be used to inform any consent conditions which might apply to the use of such vessels and any monitoring that may be required whilst they are in operation.
None.
Lincolnshire Wildlife Trust
None. None.
Dudgeon Offshore Wind Ltd
DOW believes that whilst the appropriate assessment adopts an overly precautionary approach in many areas, as detailed in our previous response dated 18th October
None.
72
Organisation Summary of response Amendments
2011, it does demonstrate that the Dudgeon Offshore Wind Farm (Dudgeon) project can be consented without having an adverse effect on the integrity of European Sites.
Section 7 of the appropriate assessment should either be significantly increased to include other potential scenarios or should be cut right back i.e. all the appropriate assessment needs to do is to make the case for the 94 Sandwich tern annual mortality threshold and not detail how it could be apportioned between projects.
However, Scenario B maximises offshore wind development within the mortality threshold level.
Section 7 of the AA is illustrative only with regard to turbine configurations. Annex 1 presents a scenario which could achieve a mortality threshold of 94 terns per annum with all sites included. Annex 2 (equivalent to “Scenario B”) identifies a bird allocation with the Docking Shoal application refused.
Para 7.29: We understand the logic used to derive this figure and do not believe at this stage that a higher threshold level would be acceptable given the current state of debate.
None. The rationale for a mortality threshold of 94 birds per annum is set out in paragraphs 7.11 to 7.20.
Minor amendments and points of clarification. Minor corrections and amendments made.
RWE nPower Triton Knoll Offshore Wind Farm design envelope and associated predicted impact on Sandwich tern was sufficiently low to enable the DECC AA to conclude an acceptable level of impact. Final work on the Triton Knoll planning application has been progressed, including an Habitats Regulations Assessment report and will shortly be submitted to the IPC (now National Infrastructure Directorate) under the Planning Act 2008.
The Triton Knoll Offshore Wind Farm application satisfies the criteria established for DECC AA‟s Scenario B (exclusion of Docking Shoal). The alternative conclusion, where all projects take a further, prorated, reduction in capacity to accommodate a much reduced Docking Shoal proposal has not been taken into account as it was not a consideration at the time of revising the Triton Knoll Offshore Wind Farm design envelope.
None.
Noted. “Scenario B” (excluding Docking Shoal from the in-combination assessment) is now included as Annex 2.
73
Organisation Summary of response Amendments
It is evident that of the two scenarios, Scenario A leads to a substantially greater reduction in the combined installed capacity of than Scenario B and therefore offering a less favourable outcome for the delivery of UK Government energy and climate change policies.
Noted
74
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ANNEX 1 An approach to identifying restrictions on s36 Greater Wash offshore wind
farm capacities
1.1 What follows is a short paper to illustrate how each project might be amended to reduce
Sandwich tern mortality. The content is illustrative only and is without prejudice to any
Ministerial determination.
1.2 Table 1 summarises the Sandwich tern collision risk predictions for each project and the
cumulative, or in combination effect, of all projects using a snapshot area of 0.141km2.
Table 1: Sandwich tern collision risk predictions for birds from the North Norfolk
Coast SPA from Greater Wash Offshore Wind Farms using a snapshot
area of 0.141km2
Site Turbine layout Avoidance rate
98.83%
Docking Shoal (Phase I - 100 MW)
16 x 6.15 MW (126m) 14
16 x 6.15 MW (145m) 13
16 x 6.0 MW (155m) 14 22
20 x 5MW (128m) 14
16 x 6.15MW (152m) 13
16 x 6.0MW (145m) 12
16 x 6.0MW (154m) 13
Race Bank (Exc. Tern Sensitive Areas) (580 MW)
94 x 6.15 MW (126m) 49
94 x 6.15 MW (145m) 45
96 x 6.0 MW (155m) 49 23
96 x 6.0MW (145m) 43
94 x 6.15MW (152m) 46
96 x 6.0 (154m) 45
116 x 5MW (128m) 49
Dudgeon (354-560 MW)
168 x 3 MW 43
118 x 3 MW 30
120 x 3.6 MW 29
85 x 6.15 MW 26
Sheringham Shoal (317 MW) 88 x 3.6 MW 1324
Triton Knoll (1,200 MW)
25333 x 3.6 MW 9
288 x 3.6 MW 8
240 x 5 MW -
150 x 8 MW -
Total (including Docking shoal 100MW scheme)
102
1.3 The projects in combination shall not exceed a mortality threshold of 94 Sandwich terns per
annum. Consequently the projects must be amended to limit Sandwich tern mortality. DECC
has made no attempt to amend Sheringham Shoal which is under construction. The remaining
81 birds (94 –13) must be allocated between the 3 s36 sites and Triton Knoll.
22
Additional turbine options supplied by Centrica 18/1/12 23
Additional turbine options supplied by Centrica 18/1/12 24
ECON completed the CRM for Sheringham Shoal so the collision risk is assumed to follow a snapshot area of 0.141km
2.
25 RWE has indicated that they no longer seek to
build this turbine configuration (RWE, 2012)
82
1.4 This approach uses the best-case turbine configuration for each site (the turbine configuration
that has the potential to generate the most MW for each bird killed) from the configurations
listed in Table 1. In practice, each developer may use fewer, larger turbines in order to
commission as much capacity as possible within the allowable mortality threshold. Turbine
selection is a commercial consideration. The turbine choice and quantity (within the Rochdale
envelope) is a matter for the developer.
1.5 Sandwich tern collision risk per turbine can be expressed as follows (Table 2) using the best
case CRM figures from Table 1:
Table 2: Collision Risk Mortality and bird mortality per turbine (assuming 98.83% AR)
Project Birds killed Turbines Bird mortality (per turbine)
Docking Shoal (Phase I) 12 16 0.75
Race Bank 43 96 0.448
Dudgeon 26 85 0.306
Triton Knoll 8 288 0.028
1.6 Sandwich tern mortality must be reduced at each project. In DECC‟s view the fairest way to
proceed is to make any reductions proportionate to the impact of each project. In terms of
effects, the closer a project lies to the Sandwich tern colony the greater the risk of bird strike.
Accordingly, Docking Shoal makes the largest reduction in proportion to its capacity, followed by
Race Bank, and Dudgeon. Given the uncertainties in collision risk modelling (i.e. a prediction as
opposed to fact); allocating terns in proportions is not considered unreasonable. DECC has
allocated terns to projects according to the relative risk each project poses – i.e. the larger the
impact the more tern mortality must be reduced.
1.7 The following calculations estimate what reduction in capacity (MW) might be required at each
project. The calculation to illustrate the required reduction in mortality is:
1. Based on the best case CRM number for each site (i.e. assumes use of best available
technology); and
2. Proportionate to the predicted CRM mortality (in line with “the polluter pays principle”).
1.8 Using the total, best-case CRM values for the four sites (above) it is possible to:
a) Express the risk each project presents relative to each other; then
b) Express the No. of terns that each project should save (according to (a)); and
c) Estimate the possible reduction on capacity and/or turbine choice.
1.9 The following figures are expressed using a coarse method for illustrative purposes only. In
practice the location of turbines which are either moved or deleted is critical – examining the
ornithological survey data could identify particular areas within each project where bird strike is
83
liable to be highest. Removing „high risk‟ turbines may present one method of reducing mortality
without the loss of capacity estimated below.
1.10 By virtue of its high mortality rate per turbine, any decision affecting Docking Shoal has a
significant repercussions on the total capacity (MW) which may be realised in The Wash.
The best case Sandwich tern mortality presented in Table 1 must be reduced from 89 birds
(across Docking Shoal (phase 1), Race Bank, Dudgeon, and Triton Knoll) to 81 birds, ie. a
reduction of 8 birds.
1.11 The following calculations express the reduction in tern mortality required from each project:
Docking Shoal (Phase 1):
12 terns x 100 = 13.483%. 13.483% of 8 terns = 1.0787 89 total CRM
Docking Shoal must save 1.0787 terns
Race Bank:
43 terns x 100 = 48.315%. 48.315% of 8 terns = 3.8652 89 total CRM
Race Bank must save 3.8652 terns
Dudgeon:
26 terns x 100 = 29.214%. 29.214% of 8 terns = 2.3371 89 total CRM
Dudgeon must save 2.3371 terns
Triton Knoll:
8 terns x 100 = 8.989%. 8.989% of 8 terns = 0.7191 89 total CRM
Triton Knoll must save 0.7191 terns
In summary the required saving, rounded to the nearest one decimal place, is: Docking Shoal – 1.1 tern Race Bank – 3.9 terns Dudgeon – 2.3 terns Triton Knoll – 0.7 terns Total – 8 terns The revised wind farm configuration is shown in Table 3:
84
Table 3: Greater Wash wind farm configuration revised to reflect an annual 94 Sandwich tern mortality limit (assuming a 98.83% avoidance rate)
Project Sandwich tern mortality
Configuration
Revised Sandwich tern mortality
Illustrative revised turbine configuration
Docking Shoal (Phase I)
12 16 x 6.0MW 10.9 14 x 6.0MW
Race Bank 43 96 x 6.0MW 39.1 87 x 6.0MW
Dudgeon 26 85 x 6.15MW 23.7 77 x 6.15MW
Total (3 sites) 81 73.7
Sheringham Shoal 13 88 x 3.6MW 13 88 x 3.6MW
Triton Knoll 8 288 x 3.6MW 7.3 262 x 3.6MW
Total (5 sites) 102 94
Note: These example turbine configurations use the best performing turbines (the turbines with the lowest predicted Sandwich tern mortality) and are illustrative of possible turbine configurations
85
ANNEX 2: An approach to allocation of Sandwich tern mortality against the Greater Wash
offshore wind farm applications excluding Docking Shoal
1.1 What follows is a short paper to illustrate how each project might be allocated Sandwich tern
mortality, assuming that Docking Shoal is not consented26
. The content is illustrative only and is
without prejudice to any Ministerial determination.
1.2 Table 1 summarises the Sandwich tern collision risk predictions for each project and the
cumulative, or in combination effect, of all projects using a survey snapshot area of 0.141km2.
Table 1: Sandwich tern collision risk predictions for birds from the North Norfolk
Coast SPA from Greater Wash Offshore Wind Farms using a survey snapshot
area of 0.141km2
Site Turbine layout Avoidance rate
98.83%
Docking Shoal (Phase I - 100 MW)
16 x 6.15 MW (126m) 14
16 x 6.15 MW (145m) 13
16 x 6.0 MW (155m) 14
20 x 5MW (128m) 14
16 x 6.15MW (152m) 13
16 x 6.0MW (145m) 12
16 x 6.0MW (154m) 13
Race Bank (Exc. Tern Sensitive Areas) (580 MW)
94 x 6.15 MW (126m) 49
94 x 6.15 MW (145m) 45
96 x 6.0 MW (155m) 49 27
96 x 6.0MW (145m) 43
94 x 6.15MW (152m) 46
96 x 6.0 (154m) 45
116 x 5MW (128m) 49
Dudgeon (354-560 MW)
168 x 3 MW 43
118 x 3 MW 30
120 x 3.6 MW 29
85 x 6.15 MW 26
Sheringham Shoal (317 MW) 88 x 3.6 MW 13
Triton Knoll (1,200 MW)
28333 x 3.6 MW 9
288 x 3.6 MW 8
240 x 5 MW -
150 x 8 MW -
Total (excluding Docking Shoal)
90
1.3 The projects in combination shall not exceed a mortality threshold of 94 Sandwich terns per
annum. Consequently the projects as described do not need to be restricted to meet the
Sandwich tern mortality limit.
1.4 The remaining 4 birds can be used to expand the turbine configurations shown in Table 1. The
Sheringham Shoal site is under construction and is already at its maximum consented capacity.
Similarly the indicative configuration at Race Bank already maximises the site capacity (96 x
26
Assuming that the Docking Shoal offshore wind farm application is refused and the proposal is no longer in the planning system and hence not considered in the Appropriate Assessment in-combination assessment 27
Additional turbine data supplied by Centrica 18/1/12 28
RWE has indicated that they no longer seek to build this turbine configuration (RWE, 2012). See Section 7.28.
86
6MW turbines = 576MW). Consequently the remaining birds can be allocated to expand the
turbine configuration for the Triton Knoll and Dudgeon applications.
1.5 One additional bird is allocated (without prejudice to the consideration of this application by the
Planning Inspectorate) to Triton Knoll (9 birds, allowing an illustrative turbine configuration of
333 x 3.6MW = 1199MW), and 2 birds are allocated to Dudgeon (28 birds, allowing an
illustrative turbine configuration of 91 x 6.15MW = 560MW). The final bird is not allocated.
1.6 The proposed wind farm configuration is shown in Table 2:
Table 2: Greater Wash wind farm configuration revised to reflect an annual 94 Sandwich tern mortality limit assuming that Docking Shoal is refused (assuming a 98.83% avoidance rate)
Project Sandwich tern mortality
Configuration
Proposed Sandwich tern mortality
Illustrative revised turbine configuration
Illustrative max capacity
Race Bank 43 96 x 6.0MW 43 96 x 6.0MW 576MW
Dudgeon 26 85 x 6.15MW 28 91 x 6.15MW 560MW
Total (2 sites) 69 71 1136MW
Sheringham Shoal 13 88 x 3.6MW 13 88 x 3.6MW 317MW
Triton Knoll 8 288 x 3.6MW 9 333 x 3.6MW 1199MW
Total (4 sites) 90 2452MW 93 2652MW
Note: These example turbine configurations use the best performing turbines (the turbines with the lowest predicted Sandwich tern mortality) and are illustrative of possible turbine configurations