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
005
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
007
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.
008
[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
010
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
012
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
013
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.
014
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
016
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
018
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.
021
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
022
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
023
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-
024
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.
027
(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
028
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
032