November 2004 (PDF 11.6 MB) - Barrick Gold Corporation

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Table 4.2.Adjustments for durationDuration of noiseIncrease in acceptable noise level at receptor, dB(A)(one event in any 24 hour period)Daytime and evening(0700–2200 h)Night-time(2200–0700 h)1.0 to 2.5 hours 2 Nil15 minutes to 1 hour 5 Nil6 minutes to 15 minutes 7 21.5 minutes to 6 minutes 15 5less than 1.5 minutes 20 10NSW industrial noise policy30
5 Meteorological conditions5.1 IntroductionCertain meteorological conditions may increasenoise levels by focusing sound-wave propagationpaths at a single point. Such refraction of soundwaves will occur during temperature inversions(atmospheric conditions where temperaturesincrease with height above ground level) and wherethere is a wind gradient (that is, wind velocitiesincreasing with height) with wind direction fromthe source to the receiver. These meteorologicaleffects typically increase noise levels by 5 to 10 dB,and have been known to increase noise levels by asmuch as 20 dB in extreme conditions, therebycausing a significant noise impact on residentsliving in areas prone to these effects.Temperature inversions occurring within the lowest50 to 100 m of atmosphere can affect noise levelsmeasured on the ground. In the geographical areaswhere this policy applies, these temperature inversionsare most commonly caused by radiativecooling of the ground at night leading to the coolingof the air in contact with the ground. This is especiallyprevalent on cloudless nights with little wind.Air that is somewhat removed from contact with theground will not cool as much, resulting in warmerair aloft than nearer the ground.In assessing noise impacts, the criteria are expectedto apply under weather conditions that would beexpected to occur at a particular site for a significantperiod of time. These include conditions of calm,wind and temperature inversions. As the criteria areexpected to apply under weather conditions characteristicof the area, it is important at the start of anoise assessment to assess the potential for suchmeteorological effects occurring, thus enablingbetter prediction of potential noise impacts. Thesections below outline the procedures for assessingtemperature inversions (Section 5.2) and wind effects(Section 5.3). Essentially, there are two underlyingapproaches to assessing these effects: the simpleand the more detailed approach.Simple approach. With the simple approach, theproponent may forego detailed analyses of meteorologicaldata and simply apply given default meteorologicalparameters to predict noise levels. Thisapproach assumes that meteorological effects arepresent for a significant amount of time, avoidingthe need to quantify these effects in detail. It isconservative, in that it is likely to predict the upperrange of increases in noise levels. Actual noiselevels may be less than predicted. This approach isgenerally used to test whether further analyses arewarranted.Detailed approach. The detailed approach involvesanalysing meteorological data to determine whetherinversion and/or wind effects are significantfeatures warranting assessment. Where assessmentis warranted, default parameters are available foruse in predicting noise or, where preferred, measuredvalues may be used instead. The detailedapproach gives a more accurate prediction of noiseincreases due to meteorological factors—as a tradeofffor the additional work involved.5.2 Temperature inversionsThe 4-step procedure for assessing the amount bywhich noise is increased by inversion effects issummarised in Figure 5.1. Assessment of impacts isconfined to the night noise assessment period (10pm to 7 am), as this is the time likely to have thegreatest impact—that is, when temperature inversionsusually occur and disturbance to sleep ispossible.Essentially, the assessment involves a stagedapproach, designed to require an assessment onlywhere initial screening tests show that inversioneffects on noise are potentially significant. Wherethe potential is established, the next step is toanalyse existing meteorological data to determinethe percentage occurrence of temperature inversions.An occurrence of 30% of the total night-timeduring winter (June, July and August) has beenselected as representing a significant noise impactwarranting further assessment. As temperatureinversions generally occur during the night-timeand early morning periods, this percentage occurrencecorresponds to about two nights per week.The night-time period for determining inversionfrequency is from 1 hour before sunset to 1 hourafter sunrise (taken to be 6 pm to 7 am), which is thetime period during which inversions are most likely.(This is different from the night noise assessmentperiod over which inversions are to be assessed,NSW industrial noise policy31
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Page 49 and 50: 1 Policy framework1.1 Overview of t
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Page 55 and 56: industry were sufficient to alter t
Page 57 and 58: Figure 1.2.The overall process of a
Page 59 and 60: Figure 1.4.Predicting source noise
Page 61 and 62: Figure 1.6.Negotiation process and
Page 63 and 64: has shown that it is a reasonable a
Page 65 and 66: Table 2.2. Modification to acceptab
Page 67 and 68: egory for the amenity criteria will
Page 69 and 70: activities, they also increase envi
Page 71 and 72: Table 3.1. Methods for determining
Page 73 and 74: Table 3.2. Determining the existing
Page 75 and 76: ambient noise levels can affect the
Page 77: Table 4.1.Modifying factor correcti
Page 81 and 82: which is from 10 pm to 7 am.) Winte
Page 83 and 84: around structures. At higher wind s
Page 85 and 86: eing used for a particular project.
Page 87 and 88: • employing ‘quiet’ practices
Page 89 and 90: 3. Control in transmission—the ne
Page 91 and 92: 8 Negotiation process8.1 The proces
Page 93 and 94: Features of a negotiated agreementp
Page 95 and 96: 9 Consent/licence conditionsThe pro
Page 97 and 98: 10 Applying the policy to existingi
Page 99 and 100: 11 Reviewing performanceMonitoring
Page 101 and 102: • the noise instrumentation used.
Page 103 and 104: ReferencesBerglund B. & Lindvall T.
Page 105 and 106: activities may include construction
Page 107 and 108: Spectral characteristics: The frequ
Page 109 and 110: Table A1. Assessment steps1. Do a p
Page 111 and 112: In this case, the amenity criterion
Page 113 and 114: any assessment period in any season
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Page 117 and 118: able to show that the wind-induced
Page 119 and 120: Take the background noise measureme
Page 121 and 122: Appendix C Procedure for assessing
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Page 125 and 126: Appendix D Estimating noise increas
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• hourly or three-hourly cloud ce
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Table E7. Aerodynamic roughness of
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Appendix FPercentage occurrence of
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282000 1354000 20-25284000 1354000
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394000 1362000 45-50256000 1364000
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366000 1372000 45-50368000 1372000
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338000 1382000 25-30340000 1382000
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310000 1392000 20-25312000 1392000
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282000 1402000 25-30284000 1402000
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394000 1410000 20-25256000 1412000
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366000 1420000 20-25368000 1420000
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338000 1430000 15-20340000 1430000
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310000 1440000 20-25312000 1440000
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282000 1450000 20-25284000 1450000
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November 2004 (PDF 11.6 MB) - Barrick Gold Corporation

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