November 2004 (PDF 11.6 MB) - Barrick Gold Corporation

Cowal Gold Project – Noise Management PlanTherefore, only Pasquil stability categories F and G are considered to be temperature inversions fornoise assessment purposes (Table 11).Using this method, an inversion can be determined by using a relationship between stabilitycategories and sigma-theta which is defined as the standard deviation of the horizontal wind directionfluctuations (σ A in degrees) (EPA, 2000).The following parameters are measured as part of the sigma-theta method:• time of day;• wind speed and direction;• surface roughness/vegetation cover; and• sigma-theta σ A (standard deviation of horizontal wind direction fluctuations).The existing meteorological station will measure wind speed and direction at an elevation of 10 m inaccordance with Table C4 of Appendix C of the INP (Appendix A). As outlined in Section E4 ofAppendix E of the INP (Appendix A), sigma-theta data will be measured on an hourly basis and wouldbe collected as specified in Australian Standard AS 2923 1987 Ambient Air – Guide for Measurementof Horizontal Wind for Air Quality Applications (Appendix B).Section E4 of Appendix E of the INP (Appendix A) states that the sigma-theta method is:‘...applied in one step to determine the daytime stability category and two steps to determine thenight-time stability category as follows:• the daytime (from 7 am to 6 pm) stability category may be determined directly from σ A datausing [Table 13].• the night-time (from 6 pm to 7 am) stability category may be determined in two steps:– determine the stability category from σ Α data using [Table 13].– modify this stability category based on prevailing wind speed using [Table 14].’Section E4 of Appendix E of the INP (Appendix A) states that the data in Table 12 is appropriate forsteady-state conditions and an aerodynamic surface roughness length of 15 centimetres (cm).Examination of Table E7 of Section E4 of Appendix E of the INP (Appendix A) indicates that theProject area surface is best characterised by rough pasture, which has a surface roughness ofbetween 4 and 10 cm. As a conservative measure, 4 cm was selected and incorporated into acorrection factor formula for Table 12.Table 12Wind Fluctuation Criteria for Estimating Pasquill Stability CategoriesPasquill StabilityCategoryABCDEFGSource: EPA, 2000Standard Deviation of the Horizontal Wind DirectionFluctuations 3,4 (σ Α in degrees)σ A ≥ 22.5 o17.5 ≤ σ A