MWA Environmental updated odour modelling for Teys Bros. abattoir to account for higher emission rates during wet pad conditions. The modelling represented emission rates 30 times higher for 48 hours after over 10mm of consecutive daily rainfall. This accounted for the period until pads dried out. Model results found the relevant odour guideline was satisfied for planned western lot subdivisions and peak odour levels there were similar to existing residential areas near the abattoir.

1. MEMORANDUM
Date: 6 April 2011
To: Peter Bittner, HWL Ebsworth
Cc: Louis Toumbas -
From: Paul King Email: paulk@mwaenviro.com.au
Re: Teys Bros. Odour Modelling – April 2011
Peter
MWA Environmental has updated the preliminary odour modelling conducted in November 2009 to incorporate the
following refinements agreed with Mr Craig Beyers (ANE) and Mr Graham Ohmsen (ERM) during the expert
witness process:
• Regional observation based meteorology generated by TAPM input to CALMET as a 3D initial guess field
rather than observations.
• Varying odour emission rates for the Holding Pens and Stock Yards represented to account for periods of
higher odour emission rate during wet pad conditions as compared to typical emission rates.
The Specific Odour Emission Rates (SOER) represented from the Holding Pens and Stock Yards were adjusted to
account for periods when the pad is expected to be wet. The SOER during wet pad conditions was modelled as
30 times higher than during dry conditions based upon data presented in Nicolas et al 2004 1 .
The higher wet pad conditions emission rates were triggered to occur following two consecutive days of >10mm
rainfall (per day). When this condition occurs wet pad conditions emission rates were represented every hour for
the two days following (i.e. 48 hours of elevated odour emissions) representing the period of time until the pad
dries out. For events when >10mm rainfall occur, for example, on three consecutive days this was modelled as
two ‘events’ and thus four days of wet pad conditions emission rates were modelled.
The rainfall data from Archerfield Airport for the Year 2008 (consistent with modelled meteorological year) was
used as a basis for assessing when wet pad conditions would occur.
th
The results of the refined odour model are presented on Figure 1 as contours depicting the predicted 99.5
percentile 1 hour average odour concentrations across the model domain with all Teys Bros. odour sources. The
results indicate that the relevant 2.5 Odour Unit guideline is readily satisfied at the western lots which we
understand are planned for subdivision as per Figure 2 attached.
It is also relevant to note that in our review of the odour dispersion modelling results that the peak odour levels at
the development shown on Figure 2 ie western lots, are within or less than those experienced at existing
residential areas to the south, north and east of Teys Bros Abattoir.
No consideration has been given in the refined modelling results to the mitigating effect of intervening vegetation.
Paul King
1 Nicholas, P., Watts, P., Heirich, N., Hudson, N., Bell, K. (2004) Development of Odour Performance Criteria for the
Australian Feedlot Industry – Part A: Sampling results – Odour Emissions from Australian Feedlots, Meat & Livestock
Australia.
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2. MEMORANDUM
FIGURE 1
MWA Environmental 6 April 2011

4. MEMORANDUM
FIGURE 2
MWA Environmental 12 November 2010