PART Response to Information Request · OPW11/0335

6.1         Management of Stormwater

           This sub-section describes the treatment train (Drawings 02 & 06) used to manage
           stormwater flowing through the Essence of Peregian development. The treatment train
           is designed to keep stormwater within the landscape of the proposed development site.
           There are three treatment units in the design treatment train:

           6.1.1       Roof Water capture

           Guttering provides capture of the rainwater incident upon the roofs of the buildings
           within the development. 100% of the roof guttering is connected to rainwater tanks,
           which provide both rainwater storage for re-use within the development, and attenuation
           of stormwater flows.

           These tanks have been sized in line with MP-4.3 of the Queensland Building Code to
           meet water savings targets, and sized are as follows
              • Beach Shacks: 3 kL
              • Building A: 100 kL
              • Building B: 100 kL
              • Hotel/Commercial Area: 100k L

           These tanks are to be provided with appropriate inlet arrangements, including first-flush
           diverters. Overflow of the tanks are to be connected to the Bioretention basins for
           treatment before release to the receiving environment.

            6.1.2     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.

           6.1.3      Blo-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.

          Flow out of the Bio-retention Trenches is underground, with filtered water percolating
          through the base of the terminal gabion wall, through a readily permeable geotextile
          layer. 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. Outflow is towards
          the terminal Wetland.

          Overland sheet-flow for the majority of the development is to be piped from stormwater
          collection pits to the bio-retention basin. For the periphery, where it is not possible to
          use stormwater collection pits, an interceptor drain, essentially a grassed swale, will be
          used to capture and divert incident stormwater to the bio-retention basins for treatment.

          Pipe and swale entrances to the bio-retention basins are to use rock basins and energy
          diffuser arrays to protect against scouring (drawing 04 & 05).


©2012 Simmonds & Bristow Pty Ltd                         Contrast Constructions                          J-1005-310 - 13 January 2012
I:\CLIENTFILES\Contrast Constructions\1108-155c - Essence of Peregian SCEP Stage 1 Update\09 Output Documents\1108-155C_SWMP
SCEMP_Scanion Property Group V3.O_ta_120113.doc                                                                           Page 8 of 24