B07056.W-01A Complete - Stormwater [As Published] · 132007.2398

                                                                                              modeling for the same catchment it was estimated the Enviropod 200 removal
                                                                                              efficiencies for nutrients were 40% for Total Phosphorous and 21% for Total Nitrogen.
                                                                                              The transform function for Nitrogen and Phosphorous for the Enviropod 200, has these
                                                                                              percentage removals as a linear relationship between influent concentration and Effluent
                                                                                              concentration.

                                                                                              The estimated removal efficiency of the Enviropod 200 is consistent with testing of the
                                                                                              CDS by the CRC which showed the CDS removed 30% Phosphorous and 13% Nitrogen.
                                                                                              The Enviropod 200 has a higher removal of nutrients than the CDS because it captures
                                                                                              finer particles and holds the retained material dry which prevents decomposition and
                                                                                              release of the nutrients, which was observed in the CRC study.

                                                                                              It is assumed an Enviropod GPT will perform the same as a generic GPT.

                                                                                              Buffa Tank
                                                                                              Buffa tank is an attenuation device. Attenuation is reduction of the peak flow of a storm.
                                                                                              Attenuation can greatly reduce the size of your treatment device. To simulate the effect
                                                                                              of the Buffa tank is suggested a sedimentation basin node be used. It is suggested that a
                      Figure 5: Sediment Removal by the Enviropod 200                         high flow bypass value be determined for the Buffa tank and the overflow weir be set to a
      Source: Auckland Cities Field and Laboratory testing for Stormwater Catch Pit Filters   width of 0m. The depth of the Buffa tank should correspond to the extended detention
                                                                                              depth. If it is indented for the Buffa tank to be used as pre-treatment a sump can be
                                                                                              added to the tank and the permanent pool volume calculated.
For the Enviropod GPT, It is assumed the system will perform the same as the generic
GPT node in relation to suspended solids
                                                                                              Effective Impervious Area
Gross Pollutants.
                                                                                              An important consideration when constructing your model is the effective impervious
The Enviropod has been tested at the University of South Australia to determine the           area terminology used for modeling in MUSIC. Effective impervious area is the directly
hydraulic and gross pollutant capture efficiency. The attached paper “Evaluation of           connected impervious area. It is a measure of the area of land that is directly connected
Gully Pit Inlet Litter Control Systems” details the results of the testing. The study         to the stormwater drainage system
showed the Enviropod captured 100%of gross pollutants up to 100 l/sec approach flow
for a gross pollutant bag. This result has been used to assume the treatable flow rate of     Table 2.2 gives an estimation of the percentage effective impervious area to the overall
the GPT bag as 50 l/sec. (See Enviropod Sizing)                                               total impervious area. The total impervious area is generally determined from analysis of
                                                                                              the proposed development layout and/or GIS and aerial images. For instance, an urban
It is assumed the Enviropod 200 will capture 100% of particles over 5mm unless the            catchment with 50% total impervious area has an effective impervious area for MUSIC
system is in bypass.                                                                          of 16%, i.e. being 31% of 50%.
                                                                                                                Urban           Commercial       Industrial       Rural            Forested
Nutrients.                                                                                                      Residential                                       Residential
                                                                                              Effective
The performance of the Enviropod in removing Nitrogen and Phosphorus has been                 Impervious Area   31              50               76               55               0
determined by a field study of the retained material in the Enviropods and corresponding      as a
3rd party modeling. Nitrogen and Phosphorous are transported in Stormwater in large                               Table 1: MUSIC Pervious and Impervious Area Parameters
                                                                                                         Source: Guidelines for Pollutant Export Modeling in Brisbane Version 7 - Draft
and small particles. Unfortunately conventional water sampling techniques do not tend to
sample large particles such as leaves. Large organic particles contain Phosphorous and
Nitrogen. The paper “Contaminate Investigation in Blackbutt Creek” details a 12month
study of nutrient capture in 80 Enviropods. Comparing the results with the third party