November 2004 (PDF 11.6 MB) - Barrick Gold Corporation

Table E7. Aerodynamic roughness of various surfacesSurface Comments Roughness (z o) (m)Water Still, open sea 0.1–10.0x10 -5Sand, open desert 0.0003Open soil 0.001–0.01GrassShort scrub, long grass and mostfield cropsMown lawn: 0.02–0.10 mRough pasture: 0.25–1.0 m0.003–0.010.04–0.100.05–0.10Forest 0.6–2Suburban area 0.6City 0.6–2E5DiscussionIn summary, the above discussion outlines threeindependent ways that readily-available or easilycollectedmeteorological data can be analysed toestimate the frequency with which atmosphericstability categories of different classes occur.It is envisaged that consultants assessing thesusceptibility of an area to inversions would eitheraccept the default meteorological parameters, orundertake their own analyses using one of theschemes outlined above.Where the default meteorological parameters are tobe replaced by the consultant’s own assessment,then any one of the above schemes could be used.However, in order of preference, the schemes are:E6Default values for the prediction ofnoise impactsOnce the percentage occurrence of stability categorieshas been determined from one of the methodsdescribed above, it is necessary to determinewhether the Pasquill Stability Category occurs for ≥30 per cent of the time during the night-time inwinter, signifying the need for further assessment.Table E8 details the default values (temperaturegradient and wind speed) to be used for the predictionof impacts where further assessment is required.1. Direct measurements of temperature gradientover a height interval of at least 50 m, withsimultaneous measurements of wind speedand wind direction at two heights.2. The sigma-theta method.3. The Pasquill-Gifford scheme and Turnerscheme (equally preferred).Other methods are detailed in the US EPA’s document(1987), On-Site Meteorological Program Guidancefor Regulating Modelling Applications.NSW industrial noise policy83