Development Application Part 2 - Environmental & Stormwater Management Plans · OPW11/0335

          Commercial Section

          1) Direction of flow from the Commercial area (hotel, restaurant roof, tank) into Wetland
          C2
          2) Direction of flow from the South balance (overland flow) and Commercial area
          (restaurant podium) into Bio-retention Cl,
          3) Direction of flow from Bio-retention C1 into Wetland C2.

          Stormwater that has passed through all these treatment units enters the receiving node
          (Appendix B). The design stormwater quality passing through the treatment units, as
          well as into the receiving node, were modelled using MUSIC Version 4.

          5.3.        MODELLING OF THE STORMWATER TREATMENT TRAIN

          Results of MUSIC modelling showed that there will be a decrease in stormwater runoff
          from the Stage 1 development area.      Loads of sediment, total nitrogen and total
          phosphorus will be substantially removed from stormwater before entering the Noosa
          National Park from the Stage 1 development area (Appendix B).

          There will be an 84% reduction in stormwater entering Noosa National Park, from 6
          MUyear to 0.9 MUyear.          The annual load of total suspended solids from the
          undeveloped commercial area is about 1000 kg/year, whereas the annual load from the
          developed site is 140 kg/year (Appendix B). Likewise, annual loads for total nitrogen
          and total phosphorus are also expected to be an order of magnitude lower than the
          present load from the existing caravan park site (Appendix B).

          Water Quality predictions from the MUSIC model (Appendix B) indicate that
          contributions of total suspended solids, nitrogen and phosphorus in treated stormwater
          from the developed site (Table 3) comply with the required water quality objectives
          (Table 1 and Table 2). The median design concentrations are expected to be below the
          required water quality objectives, and 90% of the time this should be the case (refer to
          receiving node results listed in Appendix B).

          The predicted maximum concentrations of suspended solids, nitrogen and phosphorus
          in extreme stormwater flows might temporarily exceed the guidelines (Appendix B), but
          the design concentrations (Table 3) will be improved from the existing water quality in
          the terminal wetland measured after a stormwater flow event (refer to Table 3 in
          Simmonds and Bristow, 201OErrorl Reference source not found.). The MUSIC
          modelling indicated that the treatment train for the Essence of Peregian development will
          improve the water quality of stormwater entering the terminal wetland.




©2011 Simmonds & Bristow Pty Ltd              Pacific Plumbing - Scanlon Property Group Ply Ltd                      J-1109-155 - 8 September 2011
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