RFI - Attachment F - Engineering Report

              Commercial                    1.28                     1.63                  2.91
                Urban                       0.26                     0.45                  0.72
                Base                        0.68                     1.66                  2.34
               Average                      0.74                     1.25                  1.99

                                        Table 9: Nitrogen loading Rates
The highest loading rate for nitrogen were obtained in the commercial area and at the
base catchment

The high nitrogen loading rate encountered in the commercial areas in all size particles
and at the base of the hill in the larger particles is attributed to the mechanical breakdown
of gross pollutants from the high traffic movements.

The high loading rate with fine particles is not consistent with the literature, however
these results show that in areas of high nitrogen loading and high traffic movements can
result in high concentrations in fine particulates. Street sweeping is encouraged in these
areas as it prevents the large organic gross pollutants from breaking down and becoming
more difficult to catch.

There was a low Nitrogen loading encountered at the base of the hill in suspended solids
size particles. There was also a low percentage of organic matter in this subgroup. This
is consistent with the literature (CRC 2003); however this suggests the Fine suspended
solids in the bottom of the catchment have not been generated by mechanical breakdown
of leaf material. The more probable source of the suspended solids size particles is
erosion and runoff from neighbouring properties and is further proven by the high
loading rates of phosphorous discuss latter.

                                     Nitrogen Loading Rates

              2.00

              1.50
                                                                                        Commercial
   kg/ha/yr




              1.00                                                                      Urban
                                                                                        Base
              0.50

              0.00
                           Sub 1200 Microns              Over 1200 Microns
                                             Categories


                           Figure 22: Nitrogen Loading Rates for particle size groups



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