Revised Stormwater Management Plan

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




                                         Figure 4 MUSIC Model Layout
4.5 Proposed Stormwater Treatment Train
A 20,000 litre rainwater tank is proposed to collect and treat roof stormwater runoff. The remaining
areas of the site will receive primary treatment via SPEL Stormsack’s installed in each stormwater
pit on site – Refer to Appendix D for details. The proposed tertiary treatment to discharge off site is
a Bioretention Basin. Refer to Table 5 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 5 –Type and Size of Stormwater Treatment Device
            Stormwater Treatment Device       Detail
            Catchment 1
            Rainwater Tank                                            20,000 L
            SPEL Stormsacks                                           Nine (9)
            Bioretention basin                          115 m2 Surface Area, 90 m2 Filter Area

4.6 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 6 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 6 – MUSIC Results –Treatment Train Effectiveness
                                                           Reduction        Target
                           Unmitigated    Mitigated
         Pollutant                                         Achieved        Reduction      Compliance
                             (kg/yr)       (kg/yr)
                                                              (%)             (%)
            TSS               3410           498                86             80                Y
             TP               6.39           1.16               82             60                Y
             TN               35.1           11.2               69             45                Y
            GP                 234            0                100             90                Y
Covey Associates Pty Ltd                            6                                        Project No: 161968
Consulting Engineers                                                                            100415 Rpt Iss B