SUPERSEDED Approved Plans & Document OPW25-0042 · OPW25/0042

                     6.0       STORMWATER TREATMENT & INFILTRATION

                     Treatment and disposal of runoff from the subject site will be carried out in
                     accordance with the approved document Settlers Cove Noosa Residential High
                     Density (RHD) Environmental Management Plan (EMP 1) by WBM Oceanics
                     Australia and above Conditions 46-48 & 53 of Council’s decision notice.

                     Alta Projects Engineers (formally TATE) were involved in formulation of the
                     overarching development approval document and EMP1 produced by WBM
                     Oceanics.

                     EMP1 recognises in particular the regimes of stormwater runoff and
                     infiltration which existed over the broader RHD site pre-development.

                     Essentially it was recognised that the RHD site lies atop a dune of poorly
                     graded sand with particularly high rainfall infiltration rates. As such the
                     natural state sees rainfall infiltrate the dune close to where it lands and
                     replenish the water table below with little or no runoff.

                     The standing water table forms a profile similar to the shape of the dune,
                     albeit at a depressed scale and emerges as seepage flows adjacent Noosa inlet
                     at or about RL 5.0m.

                     The zone between RL 5.0m and the inlet was recognised as having
                     particularly high ecological values, supporting numerous stands of swamp
                     mahogany and various species of fauna.

                      Critically it was recognised that these ecological values were dependant on
                     maintenance of the natural hydrogeological regime and no nett reduction in
                     rainwater infiltration post-development.

                     Section 3.1 of the EMP is reproduced below:-

                     Strategy: To ensure no net reduction of rainwater infiltrating the sand dunes
                     beneath the site. To ensure adequate treatment of runoff from landscaped and
                     hardstand areas prior to infiltration.

                     Responsibility: Consulting Engineer and Landscape Architect.

                     Management Actions: All design within the Residential High Density areas to comply
                     with the following guidelines:
                             1. All runoff from storms up to 10 year average recurrence interval (ARI) to
                             be infiltrated into the sand subgrade without runoff.
                             2. Infiltration to be achieved via swales and ephemeral streams and rapid
                             infiltration pits (RIP’s)
                     __________________________________________________________________________

                     A6769/25/SWMP/Rev OpW(A) – Feb 2025
                                                                                                  Page 5 of 9
                     SH/PL
                                               Brah101 Pty Ltd t/as ALTA PROJECTS
Document Set ID: 23646596
Version: 1, Version Date: 21/03/2025