Navitus Bay Wind Park Clarification note on matters ... · migrating adult salmon (Salmo salar); Navitus Bay Offshore Wind Park. Navitus Bay Wind Park Clarification Note ... 0.06

Navitus Bay Wind Park

Clarification note on matters relating to

migrating adult salmon (Salmo salar);

Navitus Bay Offshore Wind Park.


Clarification Note

Page ii Proportionate Assessment

Any persons intending to use this document should satisfy themselves as to its applicability for

their intended purpose.

In preparation of this document Navitus Bay Development Limited and their subcontractors

have made reasonable efforts to ensure that the content is accurate, up to date and complete

for the purpose for which it was prepared.

Neither Navitus Bay Development Limited or their subcontractors make any warranty as to the

accuracy or completeness of material supplied.

Neither Navitus Bay Development Limited or their subcontractors shall have any liability for

any loss, damage, injury, claim, expense, cost or other consequence arising as a result of use

or reliance upon any information contained in or omitted from this document.

© Copyright Navitus Bay Development Limited 2014


Clarification Note

Proportionate Assessment Page iii

TABLE OF CONTENTS

1. Introduction .................................................................................. 1

1.1 Background ................................................................................... 1

2. Clarification ................................................................................... 2

2.1 Likelihood of exposure; Monopiles .................................................... 2

2.2 Likelihood of exposure: Pin Piles ...................................................... 8

2.3 Way Forward ............................................................................... 11

3. References .................................................................................. 12

4. Figures ....................................................................................... 13


Clarification Note

Page iv Proportionate Assessment

LIST OF TABLES

Table 2.1 – Total salmon rod catches (2004 – 2012) .................................... 3

Table 2.2 – Indicative proportional exposure of migrating salmon to piling

events by month (assuming 4 hour piling duration for all 98 piles in each

month) .................................................................................................. 4

Table 2.3 – Indicative maximum number of piles that could be installed in each

month of a given year .............................................................................. 6


events by month (assuming 4 hours piling duration for each pile and

theoretical maximum number of piles installed/month) ................................ 7

Table 2.5 – Indicative maximum number of space frame foundations (4 piles at

each) that could be installed in each month of a given year .......................... 9


events by month (assuming 2 hours piling duration for each pile and

theoretical maximum number of piles installed/month) .............................. 10

LIST OF FIGURES

Figure 2.1 – Salmon Noise Contours and Overlap with Migration Channel

(monopiles) .......................................................................................... 14

Figure 2.2 – Salmon Noise Contours and Overlap with Migration Channel (pin

pile) .................................................................................................... 15


Clarification Note

Proportionate Assessment Page 1

1. Introduction

1.1 Background

1.1.1 Navitus Bay Development Limited (NBDL) (‘the Applicant’) has made

an application to the Planning Inspectorate (PINS) for a Development

Consent Order (DCO) for the Navitus Bay Offshore Wind Park (the

Project), located west of the Isle of Wight in the English Channel.

1.1.2 This clarification note has been prepared in response to comments

received from Natural England and the Environment Agency in their

Relevant Representation (under Section 56 of the Planning Act 2008)

with regards to noise exposure of migrating salmon. This note also

supports ongoing discussions on providing clarity on the realistic

worst case, potential effects arising during the construction of the

Project and the precaution embedded within the assessment

presented in the Application.

1.1.3 The note builds on clarification provided in a project paper issued on

the 13th May 2014 (NBDL, 2014) and aims to demonstrate that the

worst case scenario set out in the ES for monopile installation at 98

locations in fact represents a precautionary case in relation to what is

likely, informed by more detail on the realistic piling scenario.

Additional clarification is also presented on the pin piling scenario,

again with the aim of demonstrating the proportionate risk of noise

exposure to migrating salmon arising from the installation of space

frame foundations.

The intention of this clarification note, therefore, is to facilitate

continued discussion on potential mitigation requirements, seeking

agreement and resolving current issues ahead of the start of the

Examination.


Clarification Note


2. Clarification

2.1 Likelihood of exposure; Monopiles

2.1.1 In the ES Volume B Chapter 10 and in the clarification note on piling

(NBDL, 2014), the intermittency of noise generated by piling during

construction was highlighted in order to provide context in terms of

actual likely exposure of migrating adult salmon in the vicinity of the

project development site. It is the Applicant’s opinion that such

intermittency substantially reduces the risk of any significant impacts

arising. However it is clear from recent discussions and the issues

raised in the Relevant Representations from Natural England and the

Environment Agency that further detail and consideration of the

potential for migrating adult salmon to be exposed to noise at

≥75dBht(salmon) would be helpful in clarifying positions and in seeking

agreement on both the predicted significance of impact presented in

the ES and in the mitigation deemed to be required.

2.1.2 To this end, the tables set out below present relevant information on

the maximum number of monopiles proposed, the time taken for

installation, the relative proportions of salmon that might be expected

to be migrating in the vicinity of the piling works and a calculation of

what this might equate to in terms of the proportion of the total

population that could be exposed to noise at ≥75dBht(salmon).

a) Proportion of population in the area

2.1.3 An estimate of the numbers of adult salmon that are predicted to be

in proximity to the project has been calculated from the Environment

Agency rod catch data across the period 2004 to 2012. It is

acknowledged that the timings of presence in the project area

compared with presence in the rivers (where the salmon are recorded

caught) are likely to require the application of a temporal correction

since they cannot be in both areas at the same time, however the

Applicant wishes to discuss and agree what this might equate to with

Natural England and the Environment Agency, prior to making such a

correction. In this note, therefore, the month in which the fish are

caught is directly transposed as ‘proportion of salmon migrating’ in

the vicinity of the project area.


Clarification Note


2.1.4 Rod catch data used in the calculations is as reported in EA fisheries

statistics reports (EA, 2004; 2005; 2006; 2007; 2008; 2009; 2013a,b

and c) spanning the period from 2004 to 2012 for the following

rivers:

River Test

River Itchen

River Avon

River Piddle

River Frome

2.1.5 The records have been broken down by month across all years and a

sum total of reported catches presented for each month across all

years in order to calculate a proportion of the stock represented by

month. The proportion caught in each month is then presented as

‘proportion migrating’ in that month (noting the caveat above

regarding whether this should be corrected to more accurately reflect

inshore migration vs river migration timings). Net data (for the Hants

area/Avon and Stour/Poole Harbour) were also considered, but have

been excluded from the current calculations as netting is only

permitted between 1st June and 31st July. Data used are presented in

Table 2.1 below:

Table 2.1 – Total salmon rod catches (2004 – 2012)

River Month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Test 2 0 9 16 87 207 465 787 636 87 0 0

Itchen 0 0 2 17 38 110 280 623 613 69 1 0

Avon 0 13 48 98 192 127 102 165 6 1 0 0

Piddle 0 0 3 9 30 23 15 11 3 0 0 0

Frome 1 0 3 1 33 93 117 129 16 39 1 0

Total 3 13 65 141 380 560 979 1715 1274 196 2 0

% 0.06 0.24 1.22 2.65 7.13 10.51 18.37 32.19 23.91 3.68 0.04 0.00


Clarification Note


b) Proportion of population exposed to noise

2.1.6 Piling installation has been presented in hours, assuming each pile

takes 4 hours to install, and then expressed in terms of the maximum

number of monopiles to be installed (98) and proportion of the month

that this equates to.

2.1.7 The risk of exposure from piling during construction is then presented

in two ways. Firstly, Table 2.2 presents the potential proportion of

the salmon migrating in a given month that might be exposed to

noise (based on the maximum 1800 kJ hammer) and, as an

expression of an absolute (and unrealistic) maximum worst case

assumes all 98 monopiles required for the entire project are installed

within each (and every) month. The last row of the table presents

the outputs of the calculation including consideration of the potential

width of the available migration channel exposed to noise at

≥75dBht(salmon).

2.1.8 Adopting this approach provides a perspective on what proportion of

the migrating salmon population could possibly be exposed to noise

levels ≥75dBht (salmon), as a result of all the monopiles proposed for the

Project being installed in a single month. This is clearly over

precautionary since it would not be possible to undertake the

installation of all monopiles within one month. However, presentation

of the exposure risk associated with even this extreme case is

beneficial in clarifying the risk of exposure in such a case and

therefore, by comparison, the relative risk of exposure arising from

the Project on a more realistic basis.

Table 2.2 – Indicative proportional exposure of migrating salmon to

piling events by month (assuming 4 hour piling duration for all 98 piles in each month)


Proportion of salmon migrations (%)

0.06 0.24 1.22 2.65 7.13 10.51 18.37 32.19 23.91 3.68 0.04 0.00

Total time in month (hours)

744 672 744 720 744 720 744 744 720 744 720 744

Total piling time (hours)

392 392 392 112 384 392 392 392 392 392 392 392


Clarification Note


Table 2.2 – Indicative proportional exposure of migrating salmon to piling events by month (assuming 4 hour piling duration for all 98 piles

in each month)


Proportion of piling time/month

0.53 0.58 0.53 0.16 0.52 0.54 0.53 0.53 0.54 0.53 0.54 0.53

Proportion of salmon population that could be exposed to piling noise

0.03 0.14 0.64 0.41 3.68 5.72 9.68 16.96 13.02 1.94 0.02 0.00

At 86% exposure rate**

0.03 0.12 0.55 0.35 3.17 4.92 8.33 14.59 11.67 1.67 0.02 0.00

* Denotes piling restriction in place therefore reducing hours of piling that may be undertaken;

i.e. 8/24 hr max between 1st to 14th April and no piling between 15th April and 15th May incl.

** Denotes the proportional percentage of the total population that could be exposed taking

account of the fact that not all salmon would be migrating through areas subject to piling

noise (calculated @ 86% of the available migration channel; i.e. 86% exposure)

2.1.9 The initial figures in Table 2.2 highlight that the proportion of the

salmon population that could be exposed to piling noise range from

0% (December) to 16.96% (August) assuming all of the fish

migrating in that month will move through the area ensonified at

≥75dBht (salmon). The August value represents an extreme worst case

of noise exposure from all of the proposed monopiles being installed

in that single month. Although this is clearly a wholly unrealistic

measure, it is equally clear that even under such circumstances, a

relatively minor proportion of migrating salmon could encounter noise

at a level of >75dBht.

2.1.10 The noise propagation modelling undertaken for the Project (as

presented in Volume B, Chapter 10 Appendix 10.2 (document ref.

6.2.2.10.2)) and in Figure 10.9 of the ES chapter (Volume B, Chapter

10 (document ref. 6.1.2.10)) indicates that even during monopile

installation at the worst case (northernmost) location that produces

contour boundaries in closest proximity to the coast, at least a

portion of the available channel width is not ensonified at 75dBht or

above although it is recognised that, using the narrowest width

available, the majority (86%) is ensonified from this location. This


Clarification Note


again, however presents a worst case assumption with respect to the

proportion of the channel subject to noise at or above the 75dBht

level as locations further south within the Project area obviously

occupy less of the total available channel width.

2.1.11 A series of estimates of the area ‘occupied’ has been made for

reference and is depicted in Figure 2.1. Notably this also includes

depiction of maximum spatial extent scenarios for concurrent piling

by two vessels1, but demonstrates that even using combinations of

northern and western locations, a range of values for the proportion

of the channel is evident; a ‘realistic’ assessment might therefore

utilise the range of values (8.5% to 86.4%) to further reduce the

proportion of migrating fish potentially exposed to this level of noise.

2.1.12 The second presentation of noise exposure provides a more realistic,

but still precautionary estimate of potential risk arising from the

installation on the basis of a theoretical maximum number of

installations for each month in a given year. These numbers have

been derived from consideration of vessel and engineering logistics,

together with meteorological and metocean data to inform likely

distribution of workable days throughout the year (as discussed at

recent meetings and in the previously presented piling note (NBDL,

2014)). Theoretical maximums by month are presented in Table 2.3

below.

Table 2.3 – Indicative maximum number of monopiles that could be installed in each month of a given year, assuming two piling vessels

operating


Max No. monopiles 12 16 18 24 28 30 32 32 28 18 18 16



2.1.13 Note that in this table, the numbers relate to maximum number of

monopile installations that are theoretically possible per month based

1 Although this therefore increases the potential extent of the area ensonified at ≥75dBht

(salmon), should two vessels be used the total period within which piling is undertaken would be

reduced by up to 50%.


Clarification Note


on statistical weather data; the total therefore indicated within the

year exceeds the maximum number of monopiles proposed for the

project by almost 280% (total indicated 272; total proposed 98).

Therefore, the scenario presented is again precautionary in relation to

that which could feasibly occur as a result of the project construction.

Table 2.4 – Indicative proportional exposure of migrating salmon to piling events by month (assuming 4 hours piling duration for each

monopile and theoretical maximum number of monopiles installed/month)


Proportion of salmon migrations (%) 0.06 0.24 1.22 2.65 7.13 10.51 18.37 32.19 23.91 3.68 0.04 0.00

Total time in month (hours) 744 672 744 720 744 720 744 744 720 744 720 744

Total piling time (hours) 48 64 72 96 112 120 128 128 112 72 72 64

Proportion of piling time/month 0.06 0.10 0.10 0.13 0.15 0.17 0.17 0.17 0.16 0.10 0.10 0.09

Proportion of salmon population that could be exposed to piling noise 0.004 0.02 0.12 0.35 1.07 1.75 3.16 5.54 3.72 0.36 0.004 0.000

At 86% exposure rate 0.003 0.02 0.10 0.30 0.92 1.51 2.72 4.76 3.20 0.31 0.003 0.000


i.e. 8/24 hr max between 1st to 14

th April and no piling between 15

th April and 15

th May incl.




2.1.14 It is evident from the outputs of Table 2.4 that a minor proportion of

migrating salmon, even during peak periods, could be exposed to

noise levels at ≥75dBht (<6%). In addition, and as stated above, this

assumes that 100 or 86% of the salmon moving through the area are

exposed to noise at ≥75dBht(salmon), when in reality one might assume


Clarification Note


a lower proportion of the total, when taking in to consideration the

location of piling activity (noise source) within the project area and

the varying distance resulting from such piling from the edge of the

75dBht contour to the coast.

2.2 Likelihood of exposure: Pin Piles

2.2.1 Concerns have also been raised regarding the maximum duration pin

pile scenario and therefore additional clarification on the basis of the

risk of exposure is presented below.

2.2.2 As reported in the ES Volume B Chapter 10, the noise propagation

modelling indicates that the noise generated by the 3.5 m pin piles

will not reach the coastline for either the 90 or 75 dBht(salmon) contours.

As such there is a permanent area of sea either side of the noise

contour that, under any pin piling scenario, would be subject to noise

levels of less than 75dBht(salmon); i.e. a level below that at which any

meaningful response might be anticipated. In order to progress

discussions on the acceptability of the assessment outcomes reported

in the ES and in seeking to work towards agreement on any

additional mitigation measures, further clarification on the realistic

worst case and associated risks of noise exposure is needed.

2.2.3 To this end, and adopting the same approach as for the monopile

scenario above, a presentation of the more realistic but still

precautionary estimate of potential noise exposure risk arising from

pin pile installation is given below. Again, these have been calculated

on the basis of a theoretical maximum number of installations of

space frame foundations based on statistical weather data for each

month in a given year. The numbers have been derived from

consideration of vessel and engineering logistics, together with

meteorological and metocean data to inform likely distribution of

workable days throughout the year (as discussed at recent meetings

and in the previously presented piling note (NBDL, 2014)).

Theoretical maximums by month are presented in Table 2.5.


Clarification Note


Table 2.5 – Indicative maximum number of pin piles that could be installed in each month of a given year, assuming two piling vessels

operating


Max No. pin piles 24 32 42 52 60 70 70 76 60 40 36 30



2.2.4 The number of pin piles that are predicted for each month roughly

equates to twice the number of monopiles. As each pin pile takes

two hours to install (rather than four), the overall piling time on a

monthly basis is broadly comparable to that for the monopiles,

although differences in the pile sizes and vessels that lead to a

variation in the logistics of loading the vessel and completing the

installation of all piles. The results are presented in Table 2.6 below.

2.2.5 As with the monopile scenario, the proportion of the channel subject

to noise emission at ≥75dBht has been estimated on the basis of

some simple mapping work (see Figure 2.2). From even the most

precautionary location at the north of the Project area, it is evident

the proportion of the channel subject to noise levels of ≥75 dBht(salmon)

from pin piling activities is well below 50% of the available width of

the channel2, with the highest proportion calculated to be just under

40%. At all other locations where pin piling may be undertaken, the

proportion of the channel is lower than this figure, and from many

locations the ≥75dBht(salmon) noise contour will affect none of the

channel formed by the land masses between which salmon will

migrate to home rivers in the area. This metric has been applied to

the outputs of the calculation, in order to include consideration of the

potential width of the available migration channel exposed to noise at

≥75dBht(salmon) in the presentation of the proportion of the population

therefore potentially exposed to such noise levels.

2 It is important to note that the creation of a relevant ‘channel’ on the migration route lies

between the land masses of the Isle of Purbeck and Isle of Wight.


Clarification Note


Table 2.6 – Indicative proportional exposure of migrating salmon to piling events by month (assuming 2 hours piling duration for each pile

and theoretical maximum number of piles installed/month)


Proportion of salmon migrations (%) 0.06 0.24 1.22 2.65 7.13 10.51 18.37 32.19 23.91 3.68 0.04 0.00

Total time in month (hours) 744 672 744 720 744 720 744 744 720 744 720 744

Total piling time (hours) 48 64 84 112 120 140 140 152 120 80 72 60

Proportion of piling time/month 0.06 0.10 0.11 0.16 0.16 0.19 0.19 0.20 0.17 0.11 0.10 0.08

Proportion of salmon population that could be exposed to piling noise 0.004 0.02 0.14 0.41 1.15 2.04 3.46 6.58 3.99 0.40 0.004 0.000

At 40% exposure rate 0.001 0.009 0.06 0.17 0.46 0.82 1.38 2.63 1.54 0.16 0.002 0.000






2.2.6 From the analysis of piling times for the pin piles, it is again clear that

a minimal proportion of migrating salmon, even during peak periods,

could be exposed to noise levels at ≥75dBht assuming that a

maximum of 40% of the channel is subject to noise at ≥75dBht

(<3%). Again, the scenario considered, even with the reduction

applied for 40% of the channel ensonified at ≥75dBht, is

precautionary since the overlap between noise contours and available

channel reduces below the 40% level to effectively zero at all but the

most northerly installation locations.


Clarification Note


2.3 Way Forward

2.3.1 It is worth re-iterating that none of the numbers presented in this

clarification note are intended to describe a percentage impact on the

population; rather, the numbers are given to indicate at what level of

the population a potential exposure to noise may occur. This then

requires consideration of the interpretation of the predicted noise

levels in terms of salmon response and behavioural aspects set out in

the ES and accompanying documents.

2.3.2 In recent discussions, the Environment Agency have suggested that a

useful approach to identifying mitigation might be to identify a

maximum number of days piling per month. This would appear to be

a suitable way of defining piling controls, which would be secured

through condition on the DCO, that provides sufficient confidence for

Regulators and scientific advisors that the risk of a potential impact

upon migrating salmon adults is sufficiently low for both the purposes

of EIA and Habitats Regulations Assessment (HRA), whilst

maintaining sufficient flexibility in installation programming for the

project construction to remain viable.

2.3.3 The assessment of risk presented herein provides a basis for

demonstrating that the mitigation controls would be biologically

relevant for the species and therefore underpin a rationale for

agreement between all parties that the Project can be developed in a

manner that avoids the potential for a likely significant effect on this

Annex II species. This is an important consideration given that

Atlantic salmon are listed as primary reasons or qualifying features

for the River. Avon (Hampshire) and River Itchen Special Areas of

Conservation.

2.3.4 In order to further facilitate discussions on suitable conditions, it is

suggested that identifying a maximum permissible days of piling in a

given month is considered to be analogous to specifying a maximum

number of piles that can be installed in a given month. On this basis

a consent condition would be clearly understandable and enforceable,

satisfying the requirements of the tests for planning conditions, i.e.

necessary, enforceable, relevant, precise and reasonable.


Clarification Note


3. References Environment Agency, 2004. Fisheries Statistics 2004. Salmonid and

freshwater fisheries statistics for England and Wales, 2004.

Environment Agency, 2005. Fisheries Statistics 2005. Salmonid and


Environment Agency, 2006. Fisheries Statistics 2006. Salmonid and


Environment Agency, 2007. Fisheries Statistics report 2007. Salmonid and

freshwater fisheries statistics for England and Wales, 2007. (Declared

catches of salmon and sea trout by rods, nets and other instruments).

Environment Agency, 2008. Fisheries Statistics report 2008. Salmonid and

freshwater fisheries statistics for England and Wales, 2008. (Declared

catches of salmon and sea trout by rods, nets and other instruments).

Environment Agency, 2009. Freshwater fisheries statistics for England, Wales

and the Border Esk, 2009. (Declared catches of salmon and sea trout by

rods, nets and other instruments).

Environment Agency, 2013a. Salmonid and freshwater fisheries statistics for

England and Wales, 2010. (Including declared catches of salmon, sea

trout, eels, smelt and lamprey by rods, nets and other instruments).

Environment Agency, 2013b. Salmonid and freshwater fisheries statistics for



Environment Agency, 2013c. Salmonid and freshwater fisheries statistics for



NBDL, 2014. Navitus Bay Wind Park; Fish and Shellfish Ecology; Assessment

approach and piling installation. Dated 13/05/14.


Environmental Statement


4. Figures




Figure 2.1 – Salmon Noise Contours and Overlap with Migration Channel (monopiles)




Figure 2.2 – Salmon Noise Contours and Overlap with Migration Channel (pin pile)

Documents

Navitus Bay Wind Park Clarification note on matters ... · migrating adult salmon (Salmo salar); Navitus Bay Offshore Wind Park. Navitus Bay Wind Park Clarification Note ... 0.06