RFI - Attachment F - Engineering Report

                               Nitrogen Concentration vs. Organic Content

                            12000
   Nitrogen Concentration




                            10000
                            8000
           (mg/Kg)




                            6000
                            4000
                            2000                                           R2 = 0.7708

                               0
                                    0%        5%         10%         15%         20%         25%   30%
                                                            Organic Content (%)


                                         Figure 17: Nitrogen Loads vs. Total Organic loads
These observations have management implications as the removal of organic material or
all sizes can have a significant effect on nitrogen loads


Calculated Loading Rates
Loading rates were calculated for suspended solids, bed load, total nitrogen, total
phosphorus and gross pollutants. The total mass removed was used to estimate the loads
based on either the lab analytical data or from the grain size distribution.


Suspended Solids/Bed Loads/Gross Pollutants

Figure 18 and Figure 19 show that there was a variation in loading rate with the different
land use. The highest loading rates were encountered in the commercial area. This is
constant with the literature. High loadings were also encountered at the base of the hill.
This has a management implication for the use of at-source treatment. At-source
treatment should be focused in commercial areas and at the base of steep topography.
The figures also show that monthly loading rates across all land uses were proportional
and generally related to rainfall. This suggests that rainfall is important in determining
maintenance frequency.




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