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

          Vegetated Buffers
          Vegetated buffers provide stable groundcover, thereby minimising the erosion potential
          of the landscape surface.      Vegetation includes grassed surfaces and deep rooted
          vegetation. Energy from rainfall is dissipated over a broad, stable surface, and shallow
          sheet-flow of accumulated stormwater is slowed by the rough surface provided by the
          vegetation. The soil binding capacity of the plant roots, and the capacity of the plants to
          assimilate nutrients from infiltration water, provides the first step of the treatment train.
          Stormwater flows from the vegetated buffers into Bio-retention Trenches or directly into
          the Constructed Wetland System.

          Bio-retention Trenches
          The Bio-retention Trenches are generally dry, but during a stormwater flow the trenches
          may contain accumulated water to a depth of 200 mm, and 150 mm shortly thereafter
          when the trench is dewatering. The trenches are designed to allow passive infiltration of
          stormwater through the substrate of the trenches, and into the adjacent soil.            The
          infiltration rate is designed to allow effective assimilation of nutrients by grasses in the
          trenches, which evapo-transpire some of this water, and filter off suspended solids
          during the process.

          Flow out of the Bio-retention Trenches is underground, with collection of filtered water in
          a gravel layer that exits the trench through a Low Flow Underdrain Pipe. Flow out of the
          Bio-retention Trenches during high flow will primarily be through, and across, the crest of
          the gabion weirs. Maximum flow depths over the weir crests in the 100 year local runoff
          event are estimated to be less than 25 mm, assuming minimal flow losses through the
          gabion weir walls due to long term blockage.        Outflow is towards the Constructed
          Wetland System.

          Constructed Wetland System.
          The Constructed Wetland System features permanent water bodies that provide a final
          polishing step to stormwater flowing through the treatment train.    Suspended solids
          settle out within the standing water, and the flora and fauna within the constructed
          wetlands assimilate nutrients.    Pollutants that may enter the Constructed Wetland
          System are contained, diluted by the large volume of water in the standing water body,
          and collect in sediment at the base of the wetland system or at the water margin. The
          processed stormwater in the water column can exit the Constructed Wetland System
          through the gabion diffuser wall.

          The Constructed Wetland System provides an ecological barrier to pest flora entering
          the Noosa National Park. By maintaining local plants within the Constructed Wetland
          System, and removing weeds, the Constructed Wetland System is designed to work as
          an ecological barrier.

          5.2.        PROPOSED TREATMENT TRAIN

          This sub-section describes the proposed treatment train for stormwater management
          associated with the operating phase of the developed site (after construction is fully
          complete).   The treatment units include a Rainwater Tank, Vegetation Buffers,
          Bioretention Trenches and the Constructed Wetland System used to manage
          stormwater. The treatment train sequence is shown in Appendix B as follows:




02011 Simmonds & Bnstow Pty Ltd                Pacific Plumbing - Scanlon Property Group Pty Ltd                    J-1109-155 - 8 September 2011
I ICLIENTFILES1Contraft Conse,ct,ons11 109-1550- Essence of Pemgan SCEP Stage I UpdateW9-output Docume, IsU-1109-1SSc_SMP_Sc nbn Property
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