LATE RFI Attachment 6 - Stormwater Management Plan

SQIDEP Evaluation                                                 SPEL Basin, Sippy Downs




A number of anomalies, which have subsequently been addressed in a supplementary
report prepared by Drapper Environmental Consultants, were also seen in the qualifying
events (Table 5 in USC, 2019) and are shown below.

   •   TSS below LOD – shown in orange highlights – makes minimal difference to overall
       averages
   •   Less than 8 aliquots – shown in green. This applies to less than 20% of the total
       number of samples and therefore meets the criteria
   •   50% of storms to have at least 70% of hydrograph coverage – the supplied graphs
       seem to indicate this, but further clarification was sought and confirmed as noted
       below.

It is noted the supplementary report addressed these points as follows:

   1) A sensitivity analysis was undertaken to determine the impact of reporting at the LOD
      and 50% of the LOD. It was found by Drapper that reporting at the LOD or 50% of
      the LOD as is prescribed by SQIDEP makes about 1-2% difference. We note that
      USC was not consistent in their reporting of LOD events but this was corrected by Dr
      Drapper in the Supplementary Report.


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