Appendix 6. Odour Buffer Assessment [As Published] · 132007.2399

                                                                                            [22]
              Odour Buffer Assessment
              StarCo Developments


downwind line from the source. Errors in location caused, for example, by a shift in the mean wind
direction, can lead to larger differences between measured and observed concentrations. Taking
these factors into account, if the ranges of possible observed and modelled values do not coincide,
it is likely that there are errors in model inputs, particularly emission rates

A comparison of the odour concentrations predicted through filed intensity observations and those
predicted using the CALPUFF dispersion model under the same meteorological conditions is
presented below in

               Table 8.4: Comparison of Modelled to Observed Odour Concentrations
    Observation                 Observed Concentration                   CALPUFF Prediction
          2                             0.75 - 0.91                            <0.1 – 1.0
          4                             0.47 - 0.63                            <0.1 – 0.3
          5                             0.32 - 0.48                            <0.1 – 2.0
Notes: Model comparisons were made with CALPUFF run in 2-D mode to simplify the analysis due to the
proximity of the observation locations to the STP.




9   ASSESSMENT

Dispersion modelling of the significant odour sources within the Noosa STP using CAPLUFF has
indicated that the area of interest within the Precinct G development is marginally below the
Queensland odour guideline level of 2.5 ou. However, there are several other factors that must be
considered in assessing the potential for development within the current buffer zone.

First and foremost of these is that a temporal analysis of the predicted odour concentrations at
various times of the day indicates that it is predominantly in the early hours of the morning and
late in the evening that the predicted odour levels approach the guideline criteria.          This
corresponds to the times of day when people are usually indoors and less likely to be affected by
any adverse odour events. As can be seen in Figure 6.2 odour concentrations are not expected to
exceed 0.5 ou during the day at the proposed development site.

The second is the fact that the 2.5 ou guideline is designed to be applied to new developments or
expansion of existing facilities only. For assessment of the impact of existing facilities other
assessment techniques such as complaints records and community surveys should be given greater
weight than dispersion modelling (refer to section 3.3).

The record of odour complaints maintained by the Noosa STP indicates that since the upgrade of
the facility odour has only been problematic as a result of abnormal activity at the STP. The
CALPUFF modelling results agree with this level of complaint with the nearest residents to the STP
predicted to experience a C99.5 1-hr level of less than 1 ou under normal operating conditions. This
complaint level is also validated by the records from Noosa Springs where only one odour event
has been noted in the last 18 months (one of the three noted by the STP).

The small community survey conducted by PAE also indicates that the dispersion modelling results
reflect the impacts of odour from the STP, with only one respondent regularly noticing odours from
the STP. Both areas surveyed are approximately equidistant from the STP as the proposed
development, although the predicted odour levels are lower.

With these points in mind, together with the validation of the meteorological data used with the
data collected on site between December 2004 and February 2005, dispersion modelling appears to
provide a good assessment for the potential odour impacts on the Noosa Springs site. Of particular



1898a report final.doc                                                   PAE Job Number 1898a