BEFORETHEPALMERSTONNORTHCITYCOUNCIL______________________________________________________________

UNDER The Resource Management Act1991(RMA)

AND

INTHEMATTER ofareviewunders128(1)(c)oftheconditions of consent applying tothe Te Rere Hau Windfarm, NorthRangeRoad,PalmerstonNorth

SECTION42AREPORTBYTOMEVANS

Dated:17August2017

001

Introduction

[1] MynameisThomasRossEvans.IamassociatedirectorofResonate

ConsultingPtyLimited(TradingasResonateAcoustics)andIresidein

the state of Victoria, Australia. I am the author of reports dated

27October2016and15March2017inrelationtorevisedconditions

fortheTeRereHauWindfarmtoaddresseffectsidentifiedasaresult

of incorrect information supplied in the original application. I also

provided recommendations to ensure the conditions reflected

contemporarystandardsforoperationoftheTeRereHauWindfarm.

My background and professional qualifications are summarised in

detailinAppendixB–CVofmyreportdated27October2016.

[2] I am experienced in acoustic assessment of windfarms in Australia

and am familiar with the New Zealand standards applied to the

assessmentandmanagementofwindfarmnoise. PalmerstonNorth

City Council (“PNCC”) consulted with New Zealand Windfarms

Limited (“NZWL”) (also the “consent holder”) concerning the

appointment of an independent consultant to assist PNCCwith the

process. I was one of the nominees and was subsequently

appointed. Ihavehadnopriorrelationshipwitheithertheconsent

holderorPNCC.Myrolewastoindependentlyreviewthehistorical

materialandthedataobtainedontheoperationoftheTeRereHau

Windfarm and make recommendations as to the appropriate

conditionstomonitorandcontrolnoiseeffectsoftheexistingWTGs

andanyfurtherWTGsauthorisedbytheexistingconsent.

[3] Ihavevisitedthesiteandthedetailofmysitevisitiscontainedinmy

reportdated27October2016.

Codeofconduct

[4] I have read the Environment Court code of conduct for expert

witnesses 2014, and I agree to abide by it. I have prepared this

002

reportinaccordancewiththatCode.Ihavenotomittedtoconsider

materialfactsknowntomethatalterordetractfromtheopinionsI

express in this report. I have acknowledged the material used or

reliedonitformingmyopinionsandinthepreparationofthisreport.

Conclusions reached in the Resonate reports attached to the notice of

review

[5] ThereportsattachedtothenoticeofreviewareincludedonPNCC’s

website. There are two reports. The first is the report dated 27

October 2016 and the second is dated 15March 2017. The latter

report addresses some specific issues identified by the consent

holders (NZWL’s) acoustic consultant,MiklinHalstead in relation to

my report dated 27 October 2016. I confirm that those reports

representmy professional opinion except to the extent that I have

madeanymodificationsorchangestothiss42Areport.

[6] IhaveworkedwithPNCC’splanner,CraigAuckram,inthesettingof

conditionsinthenoticeofreview.InaseparatepartofthisreportI

addressthequestionwhetherornotanyadditionalmodificationsto

theconditionsarerequired.

[7] Themain purposes ofmy report, dated 27 October 2016, were to

reviewtheavailableinformationrelatingtonoiseemissionsfromthe

windfarmandtoadviseonsuitablenoise-relatedconsentconditions

givenboththis informationandcurrentregulatoryrequirementsfor

windfarmnoiseinNewZealand.Theinformationreviewedinrelation

tothewindfarmatthistimeissummarisedinmyreportandincluded

both the noise compliance assessment, which was undertaken by

MarshallDayAcoustics(MDA)andsummarisedintheirreportRp008

R03 2011095W dated 18 February 2014 (MDA Report), and a

spreadsheetsummarisingnoise-relatedcomplaintsreceivedbyPNCC

from 2009 through until 2016 regarding the windfarm. I highlight

003

these two items as they relate to the summary of my findings I

providebelow.

[8] In determining appropriate noise-related conditions for the

windfarm, Iwas asked to consider the site as a new proposal, and

therefore subject to thecurrentPalmerstonNorthDistrictPlanand

currentNewZealandrequirementsforwindfarmnoiseassessment,

as well as to consider knowledge of the noise generated by the

existing site. This includes the noise monitoring results presented

within the MDA Report and the agreement of all parties that the

wind turbine generators (WTGs) installed at thewindfarm produce

specialaudiblecharacteristics(SACs)inthenearfield.

Complaintsregister

[9] In my report, I provided a summary of the complaints PNCC has

received regarding noise from the subject windfarm. While

complaintsare,on theirown,notconfirmation that thesite isnon-

compliantwithreasonablenoise-relatedconditionsnoraretheyare

reasonfortheimpositionofspecificnoise-relatedconditions,theydo

provideimportantinformationonthenatureofnoiseexperiencedby

residentsaroundthewindfarm.

[10] ThePNCC complaints log I reviewed indicates that, fromMay2009

until August 2016, 1722 complaints were received from a total of

32different locations. The residents of some locations lodged a

relativelysmallnumberofcomplaints,whileconsiderablecomplaints

(greaterthan40innumber)havebeenreceivedfromninelocations.

004

[11] InreviewingthecomplaintsreceivedbyPNCC,Ihaveconcludedthat

the complaints did not necessarily relate to downwind conditions,

when noise from the windfarm would be expected to be louder.

Mostcomplaintsalsoappearedtoberelatedto lowerwindspeeds,

ratherthanmediumorstrongwinds.

[12] Additionally, many of the complaints received referred to the

character of the noise rather than simply the level of noise. These

complaintsdescribe thenoise in terms that coulddescribe tonalor

amplitudemodulationSACs,andthisissupportedbythedescriptions

ofthewindfarmnoiseintheresidentaffidavits.

OverallnoiselimitsandconsiderationofHighAmenityareas

[13] The key change in noise-related conditions for windfarms in New

Zealand that has occurred since the windfarm was originally

constructed is thatthe1998versionofNewZealandStandard6808

hasbeensupersededbyNewZealandStandard6808:2010Acoustics

–WindFarmNoise (NZS6808:2010). It is clear thatanynewnoise-

relatedconditionsfortheTeRereHauWindfarmwillneedtomake

reference to regard toNZS 6808:2010.However, certain aspects of

NZS6808:2010areunclearastohowtheywouldapplytothewind

farm, and will therefore need to be supplemented with additional

conditions.

[14] Theoverall noise limits forwindfarms that apply inmost situations

aredefined inSection5.2ofNZS6808:2010,with thenoise limitat

noisesensitiveusesbeing40dB(A)orthebackgroundnoiselevelplus

5 dB, whichever is the greater. The noise limit will vary with wind

speed as, for wind speeds where the background noise level is

greater than35dB(A), thenoise limitwill behigher than40dB(A).

Section 5.1 of NZS 6808:2010 notes that these noise limits are

appropriate for protecting the health and amenity of residents for

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most noise sensitive activities, but also notes that compliancewith

thenoiselimitsdoesnotmeanthatwindfarmnoisewillbeinaudible

atnoisesensitivelocations.

[15] AkeyaspectofNZS6808:2010thatdiffersfromthe1998versionis

that the ‘background noise level’ is defined to be the noise level

measuredintheabsenceofanynoisefromwindfarms,whetherthat

bethenoisefromotherstagesofthesubjectwindfarmoraseparate

site.TheMDAReportrelieduponbackgroundnoiselevelsmeasured

during windfarm shutdowns but was not clear as to whether the

background levels measured were influenced by noise from other

windfarms, including the TeRereHauExtensiononTararuaDistrict

CouncilLandandtheneighbouringTararuaWindFarm.Thiswillneed

tobeclarified,andthebackgroundnoisemeasurementsrepeatedif

necessary, as part of the future compliance assessment required

underthenewconditionsimposedonthesubjectwindfarm.

[16] Theexceptiontothenoiselimitsstatedin[10]isprovidedinSection

5.3 ofNZS 6808:2010which states thatmore stringent noise limits

shouldbeconsideredwhereaDistrictPlanpromotesahigherdegree

ofprotectionofamenityfortheacousticenvironmentofaparticular

area.NZS6808:2010referstosuchareasasHighAmenityareas.This

isrelevanttotheapplicationofnoise-relatedconditionsforTeRere

HauWindfarm as change decision 15A-H to the Palmerston North

District Plan recently identified particular sections of the Rural

Residential Zone that surrounds the site as ‘High Amenity’ with

specificreferencetoNZS6808:2010.

[17] Where residences are located in a High Amenity area, then

NZS6808:2010states that theminimumnoise limit foreveningand

night time periods should be reduced to 35 dB(A). Section 5.3.2 of

the Standard restricts theapplicationof this reduced limit to lower

wind speed periods, below a defined wind speed threshold. It

006

recommends that the wind speed threshold should be 6m/s, but

that ‘an alternative wind speed threshold may be applied where

justifiedonmeteorological,topographical,andacousticalgrounds.’

[18] Inmyfirstreport,Irecommendedthatthewindspeedthresholdfor

the High Amenity limits be increased to 8 m/s in the case of the

subjectwindfarm.Iconsiderthisincreasedjustifiedinthiscaseas:

(a) Themeasuredbackgroundnoiselevelsattworesidenceswithin

thedefinedHighAmenityarelow(lessthan30dB(A))forwind

speeds of up to 8 m/s. For example, the background noise

levelsat48RidgeviewRoadpresented in theMDAReportare

26-27 dB(A) up to 8 m/s for most of the considered wind

directions. This provides justification on acoustical grounds as

requiredbyNZS6808:2010.

(b) Additional acoustical justification is provided when the

potentialforSACsfromthewindfarmisconsidered.Itisagreed

that theWTGs installed at thewindfarmproduce SACs in the

near field, and this presents a risk that these SACs may be

detectableatresidencesinanareadesignatedasrequiringhigh

acousticamenity.Whilethismaynotbeareasononitsownto

extendthewindspeedthresholdto8m/s,Iamoftheopinion

thatitprovidesadditionaljustificationfortheextensionofthe

thresholdtoensurereasonableprotectionofacousticamenity

tothedesignatedHighAmenityareas.

(c) Thetopographyaroundthewindfarmissuchthatresidencesin

the High Amenity areas may be shielded when the wind is

blowing in particular directions, potentially increasing the

difference inwindspeedbetweenthewindfarm(atwhichthe

wind speed ismeasured and used for the assessment against

NZS6808:2010)andtheresidence.Therefore, Iconsiderthere

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is justification to consider a higher wind speed threshold on

topographicalgrounds.

(d) Inrelationto(c)above,andbasedonmydiscussionswithPNCC

andreviewofthecomplaintregister,somecomplaintsreceived

aboutthewindfarmrefertosituationswhereitisoperatingbut

there is little or nowind at the house to provide background

masking noise. Given that the WTGs at the windfarm only

commenceoperationat5.5m/s,ahighwind speed threshold

ofonly6m/smaynotadequatelyaddressthissituation.

I note that the extension of the wind speed threshold does not

necessarilymeanthattheHighAmenitylimitwillapplyinallcasesup

to 8m/s. Rather itmeans an investigationneeds tobeundertaken

comparing the operational noise levels to the background noise

levelsforthoseresidenceswithinHighAmenityareas,inaccordance

with Section C5.3.1 of NZS 6808:2010. An average difference of at

least 8 dB between the operational and background conditions is

requiredfortheHighAmenitylimitstobejustified.

[19] Based on the above, I have summarised the various noise limits

applicabletothewindfarmunderNZS6808:2010inTable1.Thetime

periods are as per the standard time periods from New Zealand

Standard6802Acoustics–Environmentalnoise.

Table1 NZS6808:2010noiselimitsapplicabletowindfarm

Timeperiod Windfarmnoiselimit

Allareas:Day,7am–7pm 40dB(A)orbackground+5dB,whicheverisgreater

HighAmenityareas*:Evening/Night7pm–7am 35dB(A)orbackground+5dB,whicheverisgreater

Otherareas:Evening/Night7pm–7am 40dB(A)orbackground+5dB,whicheverisgreater

*Noiselimitsfor“otherareas”applytoresidencesinHighAmenityareasifHighAmenitylimitisdeemedtonotbejustifiedfollowingassessmentinaccordancewithC5.3.1ofNZS6808:2010.

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[20] Inmeasuringandassessingoverallnoiselevelsfromthewindfarmfor

assessment against the noise limits in Table 1, the proposed

conditionsimposeadditionalspecificrequirementsasfollows:

(a) Operational and background noise levels are to be assessed

basedonmeasurementsconductedforthenighttimeperiod,

which, for the purpose of this condition, is defined as the

periodfromonehouraftersunsettoonehourbeforesunrise.

This definition is as per themeasurement specification that

wasjointlydevelopedpriortothemonitoringresultsdetailed

in the MDA Report. I consider it appropriate for the

complianceassessmenttobebasedonnight-timedataasthis

will provide a conservative assessment of windfarm noise

levels given the lower backgroundnoise levels that typically

occur at night. The definition of night in this instance is

appropriate as it will ensure that measurements avoid the

influenceof extraneousnoise, suchasbirdnoise,which can

occurwithinthestandardnighttimeperiodof10pmto7am.

(b) Theassessment is tobeseparatelyconductedbasedonfour

defined wind directions. I consider this an appropriate

approach as wind farm noise levels can vary with wind

direction and the definedwind direction sectors adequately

address the predominant wind directions that occur at the

site, as well as the different conditions under which

complaintshaveoccurred.

(c) Restrictionsareincludedontheoperationalconditionsofthe

windfarmthatcanbeconsideredintheassessment.Thisisto

ensure the exclusion of measurements taken when a

sufficientnumberofWTGsareofflineformaintenanceordue

to failure that it may noticeably reduce the noise levels at

residences.

009

(d) Aminimumnumberofvaliddatapointsforthedifferentwind

direction sectors. This is required to provide a robust

assessmentofthedifferentdirectionsectors.

SpecialAudibleCharacteristics(SACs)

[21] Anotherrelevantconsiderationforthewindfarmandtheapplication

of NZS 6808:2010 in noise-related conditions is the assessment of

SACs,namely tonalityandamplitudemodulation.While it isagreed

thattheWTGsproduceSACs,specificallytonality,inthenearfield,it

hasnotbeendemonstratedwhethertheseSACsoccuratresidences,

at leastata levelthatwouldrequiretheapplicationofapenaltyto

the measured wind farm noise level. Given the knowledge of the

near field SACs and the fact that complaints from residents often

describe the characterof thewindfarmnoise in terms that suggest

potentialSACs,Iconsideritimportantthatarigorousassessmentof

SACsfromthewindfarmberequiredbytheconsentconditions.

[22] Assessments of potential SACs at residences were documented

within theMDA Report but had limitations that I addressedwithin

myfirstreport.Additionally,Inotethattheassessmentwillneedto

be updated to address the objective assessment methodologies of

SACsrequiredbyNZS6808:2010andotherrecentguidance.

[23] For tonality, Appendix B of NZS 6808:2010 is clear that the

assessmentmethodologyfortonalnoiseataresidenceshouldbein

accordance with the Reference Method from Annex C of

International Standard ISO 1996-2:2007 Acoustics – Description,

measurement and assessment of environmental noise – Part 2:

Determination of environmental noise levels. Annex C of ISO 1996-

2:2007detailsamethodologyfordeterminingthetonalaudibilityof

ameasurementandrecommendsapenaltyscheme.Wherethetonal

audibility is less than 4 dB, no penalty is applied.Where the tonal

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audibilityisabove4dB,thepenaltyistheaudibilityless4dBuptoa

maximumpenaltyof6dB.

[24] Themainproblemthatariseswithrespect to theapplicationof the

ISO1996-2penaltiesfortonalaudibilityinthecaseofthewindfarmis

thatNZS6808appliesanapproachtowindturbinenoiseassessment

wherebyalargenumberof10-minutedatapointsarecorrelatedwith

wind speed and then averaged to determine the windfarm noise

levelforeachwindspeed.However,theaudibilityofanytonesfrom

the windfarm at a residence will be related to variable factors

including the wind speed and direction at the WTGs, and the

backgroundmaskingnoiseinthespecificfrequencyrangearoundthe

tone at the residence. Therefore, it is quite possible that, if the

windfarm produces audible tones at residences, these tones may

onlybesubjecttoapenaltyasaSACforalimitedpercentageofthe

collected10-minutedatapoints.

[25] Appendix B of NZS 6808 suggests that penalties for any tonal

characteristicsmayonlybeappliedtotheindividual10-minutedata

points ina completedataset, and theoverallwind farmnoise level

should then be recalculated from the adjusted dataset. However, I

have a significant concern that NZS 6808 does not adequately

considerasituationwhereaWTGisknowntoproduceatonalSACin

thenearfieldbutwherethischaracteristicmayonlybedetectedat

residencesundercertainconditions.Inthiscase,theapplicationofa

penalty to individual 10-minute data points will not always

adequately reflect the potential annoyance caused by a

characteristic.

[26] To illustrate thediscussion in [25]above, Iprovide thehypothetical

exampleofatonalnoisethatwouldattractapenaltyof5dBunder

ISO1996-2thatoccursfor20percentofthetimeataresidence.This

corresponds to an annoying tone that occurs with reasonable

011

regularity, and depending on weather conditions may occur

constantlyforseveralconsecutivenights.Ifthe5dBpenaltywereto

only be applied to 20 percent of the 10-minute data points, the

overall average noise level would only increase by approximately

1dB.Idonotconsiderthistoreflectthepotentialannoyanceofthe

SACinthisinstance.A1dBpenaltyisunlikelytosignificantlyaltera

compliance assessment for such awindfarm and therefore, from a

regulatory perspective, there is unlikely to be any incentive for the

operator to rectify the tone or otherwise reduce noise levels.

Additionally,InotethatthetonalpenaltiesfromISO1996-2canalso

be applied to other industrial noise sources inNew Zealand, under

NZS6802,andIwouldexpectahighertonalpenaltythan1dBwould

be applied to an industrial noise source were it to produce an

annoyingcharacteristicfor20percentofthetime.

[27] Anadditionalconsiderationregardingtonalityfromwindfarmsisthe

assessment time for individual samples. The proposed conditions

around tonality include a requirement that tonality is assessed in

two-minuteperiodsratherthan10-minuteperiods,eventhough10-

minutemeasurementsarethebasisofNZS6808.WhereatonalSAC

is detected, then the highest penalty for any two-minute period

within that 10-minute period is applied. I have recommended this

approachas, inmyexperience, the levelof tonalaudibilitycanvary

quitemarkedlyovera10-minuteperiod.Unlike thewindfarmnoise

level,which typically remains fairly steadyovera10-minuteperiod,

thelevelofaudibilityofatonecanvaryduetochanges inboththe

levelofthetonefromthewindfarmandthelevelofthebackground

masking noise. Therefore, the level of tonality assessed over a 10-

minute period may not be suitably representative of the level of

annoyance that could occurwithin that time. I have recommended

thattheleveloftonalaudibility,ifany,isdeterminedintwo-minute

periodstoaddressthispotentialvariability.Inotethatatwo-minute

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assessment period is longer than the minimum one-minute period

requiredbyAnnexCofISO1996-2.

[28] For amplitude modulation, NZS 6808 notes that some amplitude

modulationwillalwaysbepresentinaudiblewindturbinenoiseand

advises that an amplitude modulation SAC is only deemed to be

presentwhenexcessiveamplitudemodulationoccurs.AppendixBof

theStandarddetailsan ‘interimtestmethod’ for theassessmentof

excessiveamplitudemodulationbut states that ‘it isenvisaged that

appropriate objective tests for modulation special audible

characteristicswillbedevelopedinfuture’toreplacetheinterimtest

method.

[29] Given the interimnatureof the amplitudemodulation testmethod

detailed in NZS6808, I consider that it is appropriate for the

conditions to make reference to the recent amplitude modulation

assessmentmethodologydevelopedbytheUKInstituteofAcoustics,

asrecommendedina2016reviewreleasedbytheUKDepartmentof

Energy & Climate Change (DECC). The DECC reviewwas specific to

windfarmamplitudemodulationandincludedarecommendationfor

a penalty to be applied to the measured noise level where the

modulation exceeded a peak-to-trough level of 3 dB. The penalty

thatcouldbeappliedwherethisoccurredrangedfrom3dBuptoa

maximumpenaltyof5dB.

[30] Inotethattheamplitudemodulationpenaltyschemerecommended

intheUKDECCreport isclearthatanypenaltyappliesto individual

10-minutedatapointsonly,butisnotclearastowhatnumberof10-

minute data points incurring a penalty should be considered

unacceptable, rather stating that the ‘frequency and duration of

breaches’ should be considered, as well as the coincidence of the

breacheswithconditionscausingcomplaints.Where thenumberof

data points with penalties for amplitude modulation that result in

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breaches of the noise limit is considered unacceptable, it

recommends that the windfarm operator should be required to

implement mitigation. However, I do not consider this approach

consistentwiththeapproachtakentoSACsinNZS6808.

[31] Toadequately address the applicationof penalties for SACs for the

subject windfarm, proposed Condition 8 requires the following

approach:

(a) 10-minuteperiodswhichhaveundergoneananalysisforSACs

(tonalityandamplitudemodulation)aregroupedinto1m/s-

widewindspeedbinsforeachwinddirections.

(b) Ifatoneisdetectedthatattractsapenaltyandisaresultof

thewindfarm, then the applicable penalty is applied to that

period. A separate penalty is applied if excessive amplitude

modulationisdetected.

(c) IfbothtonalandamplitudemodulationSACsaredetectedin

anindividualperiod,thepenaltiesarearithmeticallysummed.

However, themaximumpenaltyapplicabletoany10-minute

periodis6dBinaccordancewithAppendixBofNZS6808.

(d) Iflessthan10percentofthedatapointsinaparticularwind

speed anddirectionbin attract a penalty for SACs, then the

penalty is applied to the individual 10-minute data points

only,and theoverallwind farmnoise level is recalculated in

accordancewithNZS6808.

(e) If10percentormoreof thedatapoints inaparticularwind

speed anddirectionbin attract a penalty for SACs, then the

arithmeticaveragepenaltyforthosepenaliseddatapoints is

determined and applied to the overallmeasuredwind farm

noiselevelforthatwindspeed.

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I consider that the above approach adequately addresses the

question of the threshold at which intermittently-occurring SACs

shouldbeconsideredtobearegularfeatureofthewindfarmnoise.If

aSAC,suchasatone,occursinfrequently(lessthan10percentofthe

time) then the effective penalty will be relatively small due to the

averagingapproachappliedbyNZS6808.However,iftheSACoccurs

morethan10percentofthetime,thenitisconsideredtooccurwith

reasonable regularity and an appropriate penalty is applied. I

considerthethresholdof10percentappropriate,andnotethatthe

samethresholdhasbeenappliedinrecentwindfarmnoiseguidelines

issuedinAustralia,namelytheNewSouthWalesWindEnergy:Noise

Assessment Bulletin, dated December 2016, and the Queensland

State code23:Wind farmdevelopment–PlanningGuideline, dated

July2017.

Requirementforacompliancenoisemonitoringreport

[32] Proposed Condition 10 details the requirements for a compliance

noise monitoring report to be submitted to PNCC to demonstrate

compliance, or otherwise, with the consent. The condition details

specificrequirementsforthereportthatIconsiderarenecessaryfor

a robust assessment of noise from the windfarm. In my report, I

notedthatitmaybepossibleforthiscomplianceassessmenttouse

theexistingnoisemeasurementdataalreadycollectedforthesite(as

documentedintheMDAReport)butnotedthat:

(a) It would need to be confirmed that the ‘background noise

levels’ measured during the windfarm shutdowns was

unaffected by noise from other stages of thewindfarm and

otherwindfarms.Ifthiscannotbeconfirmed,thenadditional

shutdownswillberequiredtoconfirmthebackgroundnoise

levelinaccordancewiththe2010versionofNZS6808.

015

(b) Tonalityandamplitudemodulationassessmentswillneedto

be undertaken using the relevant objective methodologies

detailed in the conditions. The MDA Report utilised

methodologiesthat,whileoriginallyconsideredadequatefor

the situation underwhich that assessmentwas undertaken,

havenowbeensuperseded.

(c) The tonality assessment in the MDA Report used tonality

results collected in the near field (i.e. at theWTGs) to filter

the results in the far field. While I consider this a valid

approach inprinciple, thenear fieldtonalityassessmentwas

only carried out in the downwind direction over a limited

windspeedrange. Iconsider it importantthatanynearfield

assessment of tonality consider different wind speeds and

directions that are representative of the orientation of

residences under a suitable variety of wind speeds and

directions.Thisisbasedonmypriorexperiencethatturbines

may radiate tones in other directions that are not detected

immediatelydownwindoftheturbine,andthePNCCregister

of complaints which demonstrates that a considerable

numberof complaints are receivedunder lightwindswhere

residences do not appear to be directly downwind of the

windfarm.

(d) Other, relatively minor, alterations would be required to

update the assessment such that it addresses the

requirementsofthe2010versionofNZS6808.

[33] Condition11requiresthecompliancenoisemonitoringreporttobe

independently peer reviewed by an acoustic expert acceptable to

PNCC.Iconsiderthisconditionnecessaryduetothetechnicalnature

of windfarm noise assessment, in particular the assessment of

potentialwindfarm SACs at residences. The technical nature of the

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assessmentmeans that expertise is required to provide confidence

that thecomplianceassessmenthasaddressed the requirementsof

theconsent.

Stage4ofthewindfarm

[34] Stage 4 of the windfarm is yet to be constructed and, if NZWL do

decide to construct it, then it will be necessary for a number of

conditions to bemet. These are detailed in proposed Condition 12

and require that compliance is first demonstrated for the

65currently installedWTGs prior to the installation of any further

WTGs.TheproposedConditionalsostatesthatapredictiveacoustic

assessmentwillneedtobesubmittedtoPNCCforapproval,withthe

compliance monitoring data collected for the current form of the

windfarmusedtovalidatethepredictionsforStage4.

Secondreportissued15March2017

[35] My second report, dated 15 March 2017, provided a response to

comments on my original report fromMiklin Halstead of MDA. In

certaincases, IagreedthatMrHalstead’ssuggestedchanges to the

proposed noise-related conditions were reasonable and these

changes are incorporated in the current proposed noise-related

conditions. For two items, however, I disagreedwithMrHalstead’s

suggestions; namely the wind speed threshold at which the High

Amenity condition shouldapplyand theprocess for theapplication

of penalties for special audible characteristics, particularly tonality.

My reasons for this disagreement are summarised above in

paragraph[18]forthehighamenitythresholdandparagraphs[23]to

[31]fortheapplicationofSACpenalties.

017

Proposedconditions

[36] I confirm that the proposed noise-related conditions presented for

this Hearing incorporate the recommendations of my report and,

other than where I have provided additional recommendations

withinthisStatement,reflectmyprofessionalopinion.

Differences in opinion between me and the consent holder’s acoustic

consultant

[37] Following my initial report dated 27 October 2016 PNCC, in

accordancewithamemorandumofunderstandingwiththeconsent

holder, provided the consent holder with the opportunity to

comment on that report. The comments were received from Mr

Halstead. Generally speaking, Mr Halstead agreed with the

conclusionsreachedinthereportdated27October2016,butthere

weresomemattersofdifference.

[38] Certainmattersofdifferencewere inrelationtothewordingofthe

HighAmenity condition (other than thewind speed threshold) and

theconditionsunderwhichdatapointsweretobeconsideredvalid.I

considered that the suggestions provided byMr Halstead on these

aspects were appropriate and these suggestions have been

incorporatedintotheproposedconditions.

[39] Following my discussions with Mr Halstead, the main area of

disagreement is that Mr Halstead does not believe that there is

justificationtoincreasethehighwindspeedthresholdabove6m/s,

whereasIconsiderthatthereisjustificationtoincreaseitto8m/s.

[40] Inourdiscussion,MrHalsteadstatedthat,inhisview,justificationfor

increasingthewindspeedthresholdforhighamenitywouldonlybe

justifiedwherebackgroundnoise levelswere very low (< 25dB(A))

anddidnotshowastrongrelationshipwithwindspeed.Hedidnot

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consider that these conditions were met at the subject windfarm

basedonhisassessmentofthebackgroundnoisedatahiscompany

hadcollected.

[41] Viaemail,MrHalsteadprovidedanexampleofabackgroundnoise

datasetatanothersitewherehewouldconsidertheapplicationofa

higher High Amenity wind speed threshold to be justified. The

datasetshowedatrendlinelevelbelow25dB(A)uptoapproximately

8m/s,with the trendline level only increasing by a relatively small

amountwithincreasingwindspeed.

[42] In responsetoMrHalstead’sviewontheHighAmenitywindspeed

threshold, InotethatSection5.3ofNZS6808doesnotstatethat it

excludessiteswherethereisarelationshipbetweenwindspeedand

background noise level from consideration of higher wind speed

thresholdsfortheHighAmenitylimit.

[43] The High Amenity definition in NZS 6808 states that its aim is to

protect sensitive land uses in defined High Amenity areas under

conditions in which the windfarm may be operating but the

backgroundnoiselevelislow.Theonlydefinitionitprovidesaround

thisisthataHighAmenitylimitmaybejustifiablewherethereisan

8dB difference between the windfarm noise level and the

background level. Given that the background noise levels at

residenceswithintheHighAmenityareaare27dB(A)orlessatwind

speeds of up to 8 m/s under certain wind directions, allowing a

windfarmnoiselevelof40dB(A)wouldhavethepotentialtoresultin

adifferenceinoperationalnoiselevelsof13dBormore.Therefore,I

consider it appropriate to increase the High Amenity wind speed

thresholdto8m/sinthiscasetoensurethat,wheretheremaybean

increaseinnoiselevelof8dBormoreabovebackground,theoverall

windfarmnoiseleveldoesnotexceed35dB(A).

019

[44] I also consider that the other factors identified earlier in my

statement, namely the potential difference in wind speed at the

windfarm and the residence due to topographic shielding, and the

riskofaudibleSACsatresidences,provideadditionaljustificationfor

anincreasedHighAmenitywindspeedthresholdinthisinstance.

[45] I do not view it as necessary to extend the wind speed threshold

beyond8m/sastypicallythebackgroundnoiselevelsextendbeyond

30dB(A)by10m/s.However,Idoacknowledgethatthismayleadto

increasesofmore than8dBabovebackgroundat some residences

withintheHighAmenityareaunderspecificwindconditions.Overall,

Iconsiderthatitsapplicationupto8m/swillensurethatappropriate

acousticamenityismaintainedforthoseconditionswhereitismost

likely that the windfarm will be operating but there will be a low

background noise level at the residences within the defined High

Amenityarea.

[46] One additional difference of opinion between Mr Halstead and

myselfwasthatMrHalsteadstatedthat, inhisview,NZS6808was

clearthatpenaltiesforSACsshouldonlybeappliedtoindividual10-

minuteperiodsratherthantotheoverallmeasuredwindfarmnoise

level.

[47] While I agree that this is the strict interpretation of NZS 6808, I

considerthattheStandarddoesnotadequatelyconsideroraddress

the situation where a windfarm produces intermittent SACs at a

residence as per my earlier points raised in this statement. The

potentialannoyanceofsuchSACsdoesnot,inmyview,alignwiththe

penaltythatwouldbeappliedifthosepenaltiesareonlyappliedtoa

percentageofthedatapoints.

[48] Therefore, the proposed penalty scheme sets a bar for particular

windconditionswhere,iflessthan10percentofdatapointscontain

020

aSAC,thentheNZS6808approachmaybeapplied.However,ifmore

than10percentofdatapointscontainaSAC,thenthepenaltyshould

be applied to the overall wind farm noise level determined via a

trendline,ratherthantheindividualdatapoints.

[49] In support of the above, I note that recent windfarm noise

assessmentguidanceinNewSouthWalesandQueenslandalsouses

a10percentlevelasatriggerfortheapplicationofthepenaltytothe

trendlineratherthanindividualdatapoints.

[50] It is also stated in theUKamplitudemodulation guidance that, if a

certainpercentageofdatapoints attract apenalty that results in a

breach, thenmitigation should be required. This reflects the same

approach,wherebyasmallnumberofSACsmaybeconsideredtobe

adequatelyreflectedbyasmallpenalty,butthat,atacertainpoint,

applyingthosepenaltiesonlytoindividualdatapointswithinalarge

datasetdoesnotadequatelyreflecttheannoyance.

[51] I also note that the requirement for the SAC assessment to be

grouped into specific wind speed and direction sectors will enable

targetedmitigationbyNZWLshouldSACsbedetectedthatresult in

anexceedanceofthenoiselimits.Inmyexperience,SACsarehighly

dependentonwindspeedanddirectionandthiswillallowpractical

mitigation options, should they be required, to be developed and

targetedtothosewindconditionsunderwhichtheSACsoccur.

Considerationofsubmissions

[52] Ihaveconsideredthesubmissionsfiled inresponsetothenoticeof

review. I provide a response to those that raised specific aspects

relatedtowindfarmnoisethatmayimpactontheproposedconsent

conditions.

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Submissions3and5

[53] Twoof the submissions (Submission3andSubmission5) state that

the submitter is not able to hear any noise from the windfarm at

distances of 1 to 1.5 kilometres from the site, while another

submission(Submission7)statedthatthewindfarmnoiseisminimal

attheirresidence.Iacceptthatnoteveryonewillbeabletohearthe

windfarm at all times, with audibility depending on a number of

factors including both the level ofwindfarm noise and the level of

backgroundnoise.However, I note that theproposednoise-related

consentconditionsarebasedonobjectivemeasuresofthewindfarm

noiselevel,includingobjectivemeasuresofSACs,thatareconsistent

with good practice for windfarm noise assessment in New Zealand

andelsewhere.Ifthewindfarmcanoperateincompliancewiththese

conditions,then,fromanacousticperspective,itwouldbeabletobe

operateassuch.

Submissions6,8and10

[54] Submission 6, 8 and 10 all raised concerns regarding periodswhen

windspeedatthewindfarmwassufficientfortheWTGstooperate

butwindspeedat the residencewasvery low, such that therewas

reduced natural masking of the windfarm noise. At any windfarm

site,itispossiblethattheseconditionswilloccurfromtimetotime.

Myexperiencehasbeen that theyaremore likely tooccuratnight

time,whenthedifferencebetweenhubheightandgroundlevelwind

speedtendstobehigherandthereislessnoisegeneratedbyhuman

activity, and under specific wind directions where there may be

greater shielding of wind at the residence due to the topography.

Therefore, I am satisfied that the proposed conditions address this

issue appropriately as they require separate assessments to be

carriedout foreachof thepredominantwinddirectionsat thesite,

andtheyrequiretheassessmenttofocusonthenight-timeperiod.I

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acknowledge that there will be times when the background noise

levelwillbelowandthewindfarmwillbeproducingaudiblenoiseat

residences, but note that NZS 6808 does not recommend that

windfarms be required to achieve inaudibility at noise-sensitive

locations.

[55] Submission 8 also raised a concern that itwas difficult to interpret

the meaning of the NZS 6808-based noise limits. It was suggested

that theseshouldbeviewedas the targetbut that itwas thenoise

experiencedandreportedbyresidentsthatshouldbeconsideredin

compliance.Inotethattheappropriateapproachtotheregulationof

windfarmnoise inNewZealand is to applyobjectivenoise limits in

accordance with NZS 6808, and this is acknowledged within the

PalmerstonNorthDistrictPlan.InotethatConditions16to20ofthe

proposedconditions relate to the implementationofaContactand

Complaints Procedure by NZWL that will require consideration be

giventoinformationreceivedfromresidents.

Submission9

[56] Submission 9 raised a concern regarding potential deliberate

manipulationofwind turbines during compliancenoisemonitoring,

byalteringthepitchofthebladestoreducenoiseemissions.WhileI

am not aware of any sitewhere this has occurred, I note that the

compliance assessment submitted to PNCC will need to be

independently peer-reviewed. If determined necessary by the

appointed peer reviewer, it may be appropriate for the electrical

output data from the WTGs over the monitoring period to be

providedforthereview.

[57] Submission 9 also expressed significant concerns with respect to

potential amplitude modulation from the WTGs installed at the

windfarm. This included a concern that the specified amplitude

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modulationassessmentmethodologyintheproposedconditionswas

not sufficiently accurate in detecting amplitude modulation. In

response to this, I note that it is not possible to comment on the

unpublished research referred to in the submission regarding the

Institute of Acoustics amplitudemodulationmethodology but note

thatthismethodologyhasundergoneextensivetesting,andhasbeen

publishedbythepeakbodyforacousticiansintheUK.Inmyopinion,

I consider the Institute of Acoustics methodology to be the best

availableassessmentmethodologyforamplitudemodulationofwind

turbinenoise.

[58] Itwas also recommended by Submission 9 that the SAC penalty of

6dBbeappliedinfullregardlessofanySACtesting.Idonotconsider

thisappropriateand it isnotconsistentwiththeapproachrequired

byNZS6808.SACshavebeenshowntooccurinthenearfieldofthe

WTGs but, to date, have not been objectively identified at

residences.GiventheoccurrenceofSACsinthenearfield,Iamofthe

opinion that a robust SAC assessment methodology is required at

relevant residential locations, and consider that the methodology

requiredbytheproposedconditionsissuchamethodology.

[59] A final concern of Submission 9 was the need for verifiable

compliance testing and, as requested in the submission, ongoing

‘live’orreal-timetestingofthewindfarm.Withrespecttotheneed

forverifiabletesting,Iagreethatanindependentpeerreviewofany

compliancetestingisrequiredandnotethatthisisconditionedinthe

proposed consent.However, I donot consider that there is a need

for ongoing ‘live’ or real-time monitoring of windfarm noise. My

reasonsforthisare:

(a) ‘Live’ monitoring of windfarm noise is not feasible as the

NZS6808 assessment methodology, as specified in the

proposed conditions, requires a sufficient number of 10-

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minute data points to be collected and analysed for an

assessmenttobeconsideredvalid.Theassessmentisnotofa

single10minuteperiod.

(b) Thesignal-to-noiseratioofwindfarmnoiseatresidencesand

atadistance fromthewindfarm isoftenrelatively low,with

thewindfarmnoiselevelatorclosetothebackgroundnoise

level.Therefore, inmyopinion, ‘live’monitoringsystems for

windfarmsare likely tobe subject to significant interference

fromextraneousnoise,andwilllikelyreturnahighnumberof

false‘exceedances’.

(c) In my experience, windfarm noise levels remain relatively

steady (for a given wind speed and direction) over many

years.However,ifthereisareasontobelievetherehasbeen

a change in noise levels, I consider that the proposed

conditions enable noise emissions to be managed into the

future.

Submission11

[60] Submission 11 summarised a detailed analysis of resident logs and

complaintsthathadpreviouslybeenundertakenbythesubmitter.It

concluded that complaints referred primarily to the wind direction

sectors identifiedintheconsentconditionsandtypicallywhenwind

speedatthewindfarmisintheregionof8–10m/sinthesoutheast,

and6–8m/sinthenortheast.Aspermyreviewofcomplaints,the

reviewidentifiedthatcomplaintsdodiscussnoisefromthewindfarm

intermsthatsuggestpotentialSACs.

[61] I note that the proposed consent conditions will require that a

detailed SAC assessment will be undertaken to address the wind

speedanddirectionsidentifiedinSubmission11.

025

[62] The proposed conditions impose a High Amenity limit on certain

residencesforthelowerwindspeedrangeofupto8m/s.Aspermy

earlier statements, I do not consider it reasonable, based on the

availablebackgroundnoisedata,toextendtheHighAmenitylimitup

tothe10m/sreferencedinSubmission11.However,Inotethatthe

assessmentofwindfarmnoise,includingSACs,willneedtoextendto

wind speeds of up to 15.5 m/s. Therefore, I consider that the

applicationoftheconditionswillrequireassessmentofthoseperiods

wherethevastmajorityofcomplaintshavebeenreceivedfromthe

residents.

Submission12

[63] Submission 12 raised a number of suggested changes to the

proposedresourceconsentconditions,and Ihaverespondedtothe

suggestionsthatimpactonthenoise-relatedconditionsbelow.

[64] The first suggestion is that thewind conditions asmeasuredat the

windfarm mast will be different to that at the residences. My

experience tells me that it is likely that there will be a difference

between the wind at the mast and the wind at the residences.

However, I note thatNZS6808 requireswind speedmeasurements

to be takenwithin thewind farmand at theWTGhubheight, and

therefore the nominated western mast location is an appropriate

measurementlocation.Irefertomyresponseinparagraph[54]asto

othermeasures incorporated intotheconditionstoaddressperiods

oflowwindspeedatresidencesinparticular.

[65] Submission 12 also states that all residences on Ridgeview Road

shouldbeconsideredHighAmenityareas. Inote that thedefinition

ofHighAmenityAreasisamatterforPNCCbutthat,asthewindfarm

willberequiredtocomplywiththeHighAmenityconditionatsome

residences onRidgeviewRoad, noise levels at other residenceswill

026

also effectively be controlled to the same condition due to the

relatively close proximity of these residences. Therefore, I do not

considerthattheextensionoftheHighAmenityoverlayinthePNCC

District Plan to all residences on Ridgeview Road would have any

noticeableeffectonnoiselevelsfromthewindfarm.

[66] Arequestwasmadethatthewindsectorsspecifiedintheconditions

‘shouldbecheckedsothattheymatchthenaturaldistributionofthe

wind’. I confirm that Ihave reviewedannualwinddatacollectedat

thewindfarmmastforboth2014and2015andthenominatedwind

directionsectorsaddressthevastmajorityofconditionsthatoccurat

the site. There will be periods that fall outside of the nominated

sectors during any assessment period but these appear to be very

limited in number and it would not be appropriate to conduct a

compliance assessment on that occasional occurrence of different

winddirections.

[67] Suggestion H of the Submission is that Condition 7.4 should be

amendedtorequireWTGstobegenerating,ratherthan‘onlineand

availableforgeneration’,foradatapointtobeconsideredvalid.The

reason for thecurrentdefinition is that therewillbeperiodsat the

lower end of the defined wind speed range where WTGs will be

online but the natural variation of wind speed across the site will

meanthatthewindspeedattheWTGwillnothavereachedcut-in.

Asthisispartofthenaturaloperationofthesite,Iamsatisfiedthat

thecurrentconditionisappropriatebutnotethat:

(a) Giventhattheremaybedatapointsat6m/swhereWTGsare

not operating due to local wind speed (below 5.5m/s), bin

analysis of the data would be preferable as per C7.4.2 of

NZS6808. This would ensure that the result at higher wind

speedswouldnotbeinfluencedbyanyofthesedatapointsat

6m/s.

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(b) Iwould expect that the compliance noisemonitoring report

requiredunderCondition10wouldconsiderthegenerationof

the site during the monitoring and, if NZWL opt not to

operate certain WTGs under particular conditions, that this

wouldbeidentifiedinthereportasaconditionthatthenoise

monitoringresultswerecollectedunder. Iwouldalsoexpect

that the peer review of the report required under

Condition11wouldconsiderthis.

[68] Suggestion IofSubmission12states thatCondition7.5.2 shouldbe

amendedtodefineaminimumnumberofdatapointsforeachofthe

SSE and ESE wind direction sectors. The condition has been

documentedassuchtoallowtimelyreportingofresults,inlinewith

otherconditionsofconsent,andIamsatisfiedthatit,alongwiththe

requirements for the assessment of SACs across the range ofwind

speeds and wind directions defined, will result in an adequate

assessmentofwindfarmnoise.

[69] Suggestion J of Submission 12 suggested an approach to the

assessmentof tonal sound that, basedonmyunderstandingof the

submission, is equivalent to the methodology already required by

NZS 6808. Annex C of ISO 1996-2 requires that the tonal energy is

determined and then the masking/background energy in the

frequency band immediately around the tone is determined. The

differencebetweenthetwoisusedtodeterminetheaudibilityofthe

tone.Thismethodologyhasbeendeterminedbasedontheoutcome

of subjective listening tests and I consider it an appropriate

methodologyforthedeterminationoftonalityandtonalaudibility.

[70] Suggestion K of Submission 12 requests consideration of On/Off

testing.On/Off testing is defined in Section7.7ofNZS6808. Inmy

experience,On/Offtestingcanbeinconclusiveasit issubjecttothe

specific short term background noise and operational conditions at

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the timeof the test. I consider the longer term testing requiredby

the proposed consent conditions to provide a more robust

assessment methodology, particularly for SACs which are highly

dependent on the background noise at themeasurement location.

Longertermtestingprovidesaclearerindicationoftheoccurrenceof

SACsasitprovidesmeasurementoverawiderrangeofconditions.

[71] Suggestion L of Submission 12 states that there is a lack of clarity

aroundthetimeframesintheproposedconditions,particularlywith

respect to the assessment of noise during the daytime and the

definition of the evening period. Upon review of the currently

proposed conditions, I agree that these aspects should be better

definedandhaveprovided recommendations toaddress thisat the

endofthisstatement.

[72] Suggestion M of Submission 12 states that mitigation should be

implemented to address the complaints of residents. From an

acousticperspective, Idonotagree this isnecessary.That is, if the

windfarm can operate in accordance with the proposed consent

conditionsthenIwouldconsiderittoprovideanappropriateacoustic

outcome.

[73] The final requestof Submission12 is for a condition related to the

measurementofinfrasoundfromthewindfarm.Infrasoundissound

atvery,verylowfrequenciesand,duetothehighhearingthreshold

at these frequencies, typicallywell below the threshold of hearing.

Modernwindfarmsdoproduceinfrasoundbut,inmyexperience,the

levelofinfrasoundthatoccursatresidences,andindeedevenatthe

WTGs themselves, is well below the threshold of perception. NZS

6808 does not require the assessment or measurement of

infrasound, and it is not appropriate to classify it as a SAC, and

therefore I do not consider it appropriate to include the suggested

condition.Additionally,basedonmyexperience,Idonotconsiderit

029

necessarytoincludesuchaconditionbecausethelevelofinfrasound

atresidences is likelytobesignificantly lowerthanthethresholdof

perception. I note that none of the complaints lodged with PNCC

refer to thewindfarm in away that indicates potential infrasound,

withthecomplaintsclearlyreferringtoaudiblenoise.

Recommendedconditions

[74] InreviewingtheproposedconditionsofconsentinthePNNCNotice

ofReview, Ihavenoted some recommendedchangesbelow.These

are a result of specific concerns raised by submissions received on

thereview.

[75] Firstly, I recommend that the last paragraph of Condition 4 be

rewordedasfollows(changeboldedforemphasis):

This condition only applies twelvemonths after the conditions have

been amended pursuant to PNCC’s review under RMA, s 128(1)(c),

from 7 pm to 7 am, up to a hub height wind speed of 8m/s and

where the difference between operational and background noise

levels is greater than 8 dB(A) in accordance with Section C5.3.1 of

NZS6808:2010,otherwisecondition5applies.

[76] Iconsiderthischangeimportantbecause,asidentifiedbySubmission

12,thereispotentialconfusionaroundthedefinitionofeveningand

night time given the definition of night given in Condition 7.2. The

time definitions given above are consistent with the standard

definitionsofeveningandnighttimeunderNZS6802(asreferenced

byNZS6808)butIconsiderthatthespecificdefinitionoftimesinthis

condition provides additional clarity to the time at which the High

Amenitylimitsmayapply.

030

[77] For thesamereasonas theabove, I recommendthatCondition7.2

be reworded as follows to assist with clarity (change bolded for

emphasis):

Theoperational andbackgroundnoise levels are to beassessed for

theperiodfrom1houraftersunsetto1hourbeforesunriseonly.

Theremovalof thephrase“nighttime”fromthisconditionreduces

potentialuncertaintywithvaryingdefinitionsofthisterm.

[78] Myfinalrecommendedchangeistoaddresstheconcernthat,asthe

assessment only requires assessment during the evening and night

time period, it is not clear how any exceedances during daytime

would be addressed, should they occur. It is quite possible that an

exceedance would only occur at night time, due to higher

backgroundnoise levelsduringthedaytimeand lessstringentnoise

limits for residences in High Amenity areas, but this needs to be

demonstratedbytheconsentholder.

[79] Considering the above, I suggest the following additional condition

(Condition10.7)beaddedtotheconsent:

Ifanymitigationmeasuresareidentifiedwithinthecompliancenoise

monitoring report, then evidence shall be provided that these

measureshavebeenappliedatalltimesofday,unlessjustificationis

providedwithinthecompliancenoisemonitoringreportastowhythe

mitigationmeasuresshouldbelimitedtospecifictimesofday.

[80] I consider that the above suggested condition would address the

concernarounddaytimenoiselevels,requiringtheconsentholderto

justifywhyanymitigationshouldonlyapplyduringspecificperiods.

This justification will need to be included in the compliance noise

monitoring report andwill therefore be subject to the peer review

requiredunderCondition11.

031

Conclusion

[81] With the incorporation of my recommendations above, which I

understandhavebeenmadeintotheproposedconditionspresented

by PNCC, I consider that the proposed noise-related conditions are

appropriate basedonmy site visit, the information I have received

andreviewedregardingthecurrentsite,andoncurrentregulationof

windfarmnoiseinNewZealand.

Date: 17August2017

___________________________TomEvans

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