November 2004 (PDF 11.6 MB) - Barrick Gold Corporation

Appendix C Procedure for assessing noise increasedue to temperature inversionsC1IntroductionThe procedure for assessing the increase in noisecaused by temperature inversions involves thefollowing main steps:• Do an initial screening test to determinewhether there is the potential for increasednoise levels due to inversions, and whetherfurther detailed analyses are warranted.• Determine the extent of impact. Where thereis the potential for inversions to increasenoise levels, the actual extent of impact (interms of percent occurrence of inversions) forthe locality being assessed is to bedetermined. Where inversions are predictedfor more than 30 per cent of the total nighttimeduring winter, these are considered to besignificant and should be taken account of inthe noise assessment.• Predict the level of noise using default oralternative parameters to determine theincrease in noise levels expected due toinversions. Default inversion parameters arespecified to avoid the need for potentiallycostly on-site monitoring, but, if preferred,other values based on direct measurementsmay be used.• Assess the impact to determine whether theincreased noise levels due to inversions willaffect receivers in the vicinity of thedevelopment. The predicted increased noiselevels are compared with the project-specificnoise levels to determine if any exceedances(and hence noise impacts) are expected.Table C1. Initial screening test proceduresTest1. Night-timeoperation2. Test formaximumpossible levelof impactProcedureDetermine whether the development in question operates at night (2200 to 0700).If the development operates at night, do screening test 2 to determine the potential forimpact.If the development does not operate at night, there is no potential for noise impact dueto inversions, and no further consideration of these effects is required.Do a noise-prediction assessment, assuming the following meteorological conditions torepresent the upper level of impacts:Non-arid areas (average annual rainfall 500 mm or more)• temperature inversion strength: 3°C/100 m• source-to-receiver drainage-wind speed where applicable 1 : 2 m/s at 10 m heightArid and semi-arid areas (average annual rainfall less than 500 mm)• temperature inversion strength: 8°C/100 m• source-to-receiver drainage-wind speed where applicable 1 : 1 m/s at 10 m heightIf the predicted noise levels show an increase of less than 3 dB, meteorological effectsare not considered to be an issue and no further consideration of these effects isrequired.If a greater than 3 dB increase is predicted, meteorological effects are an issue andfurther work is needed to determine the meteorological conditions applicable to the sitein question. (See Table C2.)(Table D1 in Appendix D may be used as a guide to predicting the effect ofinversions for this Step.)Note:1. The drainage-flow wind default value should generally be applied where a development is at a higheraltitude than a residential receiver, with no intervening higher ground (for example, hills).NSW industrial noise policy73