Stormwater Management Plan

                              STORMWATER MANAGEMENT PLAN
Client: Hass Holdings ATF The Quasar Trust                                         Location: Taylor Court, Cooroy

                                Table 3 – MUSIC Source Node Attribute Summary
                                                                        Area
                                         Source Node
                                                                         (ha)
                                              Roof                      0.096
                                             Road                       0.437
                                          Landscaping                   0.181
                                           Hardstand                    0.042
                                        Untreated Road                  0.054
                                     Untreated Landscaping              0.013
                                             Total                      0.823

4.4 Proposed Stormwater Treatment Train

The development has been modelled as one (1) catchment with the following mitigation measures
proposed. Refer to Stormwater Management Plans in Appendix B for details.

Stormwater runoff from the site will be treated by a Bioretention Basin prior to discharge off site.
Refer to Table 4 for bioretention basin sizing. Filter media is established to a depth of 0.5 m, with a
0.1 m and 0.2 m transition and drainage layer, respectively. The extended detention depth is 0.3
m.

                             Table 4 –Type and Size of Stormwater Treatment Device
            Stormwater Treatment Device         Detail
            Catchment 1
            Bioretention basin                            115 m2 Surface Area, 115 m2 Filter Area

4.5 Pollutant Reduction Results

MUSIC modelling of the proposed stormwater treatment strategy for the site was performed to
ensure the identified load based pollutant reduction objectives were achieved. MUSIC version 6.2
has been used to model the effectiveness of the designed stormwater treatment trains.

The target reductions in stormwater pollutants are based on a comparison of an unmitigated
scenario i.e. having no treatment on site, and the mitigated scenario, which has stormwater
treatment measures incorporated into the site. The results of the MUSIC models for the each
catchment and the overall site can be found in Table 5 and demonstrate that compliance has been
met or exceeded for all the required pollutant load reduction objectives stated in the State Planning
Policy (2014) at catchment and site level.

                             Table 5 – MUSIC Results –Treatment Train Effectiveness
                                                              Reduction          Target
                           Unmitigated      Mitigated
      Pollutant                                               Achieved          Reduction       Compliance
                             (kg/yr)         (kg/yr)
                                                                 (%)               (%)
          TSS                 3380             687                 80               80               Y
           TP                 6.54             1.61                75               60               Y
           TN                 35.3             14.8                58               45               Y
          GP                  234              19.7                92               90               Y

As the results in Table 5 demonstrates, the stormwater quality management strategies proposed
for the proposed Highway Service Station meet or exceed the target reduction rates required by
the NSC and the State Planning Policy (2014).




Covey Associates Pty Ltd                              5                                        Project No: 161968
Consulting Engineers                                                                              100415 Rpt Iss A