RFI - Attachment F - Engineering Report

Removal loads and Intensity

                               Loads and Peak Intensity




                                                             Peak Rainfall Intensity
                        1800                            10
                        1600                                                            Total
     Total loads (kg)




                        1400                            8                              Removoed




                                                                  (mm/6mm)
                        1200                                                           (kg)
                        1000                            6
                         800                                                           Peak
                                                        4                              Intensity
                         600
                         400                            2                              (mm/6mins)
                         200
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                               Month


                               Figure 5: Loads vs. Peak Intensity.
It is apparent that there may be a relationship between rainfall and intensity. A
comparison of Figure 3 and Figure 5 shows that loads stayed the same in December,
despite the drop in rainfall; however there was a storm with high peak intensity in
December. This storm would have created high overland flow velocities which would
have mobilised larger particles into the Enviropods, especially for the steep grades
encountered in the Blackbutt catchment.

Figure 6 below show there may be some relation between peak intensity and gross
pollutant capture (R2=0.67). This correlation from a small data set suggests further
investigation could be carried out on the relationship between rainfall depth, intensity and
load. Possibly there is a threshold of intensity that will mobilise gross pollutants




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