Pre-Request Response Application 132001.210310.1

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    Table 2 Mean Annual Pollutant Loads              -
                                                         Base Case and Developed Mitigated Site (Modelling
                                     Period 1/1/1998 -1/1/2002)     -
                                                                        Entire 65 ha site

                                                                                    30.5 ha Developed
                                                  65ha Base Case Site
                            Parameter                                             MItigated Site + 34.5 ha
                                                      (ForestedSite)                  Forested Buffer
                           Flow (MUYr)                      426                              431

                            TSS (kg/yr)                    36,500                           32,300
                                TP (kg/yr)                  37.0                             41.8

                             TN (kg/yr)                     422                              490




The pollutant exports from the entire site are seen to decrease for suspended solids, but increase for
total nutrients. This also assumes that the large external buffers to the site do not improve
stormwater quality in passage through them.

                                                                                                               1
When these results are considered in the context of typical stormwater management targets that
are applied to most developments, the requisite standards are met, as shown in Table 2.



    Table 3 Mean Annual Pollutant Load Reductions -Developed Mitig ted Site Only (Modelling
                                               Period 1/1/1998 -1/1/2002)

                                                Pollutant Load Reduction            Normal Development

                            Parameter          30.5 ha Developed Mitigated Site             Target
                                                   compared to Developed
                                                      Unmitigated site
                           Flow (MUyr)                     24.9%                             NA

                            TSS (kg/yr)                    80.7%                             80%
                             TP (kg/yr)                    68.9%                             60%
                             TN (kg/yr)                    52.4%                             45%




The   incorporation of the detention basin upstream of Dodonaea Close will serve to detain
stormwater emanating from       an approximate 2.8 ha forested catchment on the opposite site of

Beckmans Road. The detention basin is likely to primarily serve a hydraulic control function by
attenuating peak flows through a culvert under the road. The requirement for flow attenuation at this
point relates to the integration of the site stormwater management systems with that of the adjoining
development.

If you have any questions regarding the above advice, please contact Damion Cavanagh on 026687
0466.

Yours Faithfully
BMT WBM Pty Ltd




         fV\’;_     ~~~

Damion Cavanagh
Associate




1
    SPP Healthy Waters      -
                                comparison of developed unmitigated versus development mitigated. It should be
noted that the assessment considers only the developed portions ofthe site and excludes undeveloped portions
i.e. the very large external buffer area outside of the defmed development extent.




C:1B15573.c.dcclF B15573 013.doc                                                             A part of BMT in Energy and Environment