2016-04-19 P&E Committee - Item 1, Attachment 2 - Air Quality Assessment Report

4           Ausplume Dispersion Modelling
4.1         Modelling Approach
The Ausplume model (version 6.0) has been used in this assessment. Ausplume is an approved
Gaussian plume dispersion model for regulatory assessment in Queensland. The model accounts for
meteorological data, building wake effects and terrain effects in the prediction of ground level
concentrations of pollutants from stack, area or volume sources. Ausplume assumes steady state
meteorology for the field of influence of the source being considered.

Steady state meteorology assumes that for any given time period of model calculation (usually
1 hour), the wind and other meteorological conditions are uniform over the entire area being
modelled, and that a plume is assumed to travel instantaneously to the edge of the modelled area in
a straight line. A number of additional parameters are considered in the modelling. Each of these
parameters is considered in the following sections.

Given the relatively simple terrain in the surrounding area and the small separation of source and
receptor, adoption of a Gaussian plume dispersion model such as Ausplume is considered
appropriate.


4.2         Receptors
Terrain data for the area surrounding the development was obtained from the Digital Elevation Model
(DEM) 25 Metre Grid of Australia derived from LiDAR model, which represents a National 25 metre (bare
earth) DEM that has been derived from some 236 individual LiDAR surveys between 2001 and 2015.
Terrain heights for a total of a 1 km x 1 km grid (10 m intervals) surrounding the proposed
development was included in the dispersion model to account for ground height variability. In
addition, a total of 72 discrete receptors covering the nearby sensitive receivers were included in
the model at heights of 1.5 m, 4.5 m, and 7.5 m above ground level.


4.3         Meteorological Data
A site specific meteorological dataset has been determined using the prognostic model TAPM (The Air
Pollution Model). Prognostic models, such as TAPM, permit the development of localised
meteorological datasets, based on synoptic weather conditions. The model predicts the regional
flows important to dispersion, such as sea breezes and terrain induced flows, against a background
of larger-scale meteorology provided by synoptic analyses. The output of this model, when used with
a diagnostic meteorological model, such as Calmet, provides a meteorological dataset suitable for
introduction into the diagnostic wind field results.

Predictions of meteorological parameters for the region in the surroundings of the development site
were undertaken using TAPM (Version 4). The model was configured with a series of nested grids
chosen to provide an appropriate communication and transfer of information from the broad synoptic
to the local scale.


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                            Synergy Property Partners Pty Ltd- Air Quality Assessment - Proposed Service Station, 123 Eumundi-Noosa Road, Noosaville
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