RFI - Attachment F - Engineering Report

Surprisingly lower loading rates for phosphorous were encountered in the suspended
solid size particles than in the bed load and gross pollutants. This is inconsistent with the
literature. As suggested one of the principle sources of phosphorous is rock erosion. It is
possible that the eroded particles are continuing to erode and break down as they travel
with in the runoff. Capture of these particles before they enter the reticulation system
prevents further break down. All studies in the literature have tended to sample
stormwater at a downstream point for an entire catchment allowing entrained particles to
brake down in the reticulation system before they are sampled. This would explain the
higher loading rates in larger particles encounter in the Enviropod.


                                Phosphorous Loading Rates

              0.50

              0.40
                                                                                        Commercial
   kg/ha/yr




              0.30
                                                                                        Urban
              0.20
                                                                                        Base
              0.10

              0.00
                           Sub 1200 Microns           Over 1200 Microns
                                            Category


                       Figure 25: Phosphorous Loading Rates for particle size groups


PHOSPOROUS                        Sub 1200 Microns       Over 1200 Microns             All Particles
                                      kg/ha/yr                kg/ha/yr                   kg/ha/yr

              Commercial                 0.36                   0.38                       0.74
                Urban                    0.07                   0.08                       0.15
                Base                     0.30                   0.43                       0.73
               Average                   0.24                   0.30                       0.54

                                   Table 10: Phosphorous loading Rates




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