Attachment 7B - Site Based Stormwater Manamgment Plan by ADG

                                                                    RACV Noosa Resort: 94-142 Noosa Drive, Noosa Heads

                                                                              ADG Ref: 22366 C R10 Rev04 14.12.22.docx

                                                                                                        December 2022


 5       STORMWATER QUANTITY ASSESSMENT
          The aim of the stormwater quantity assessment is to ensure that the development shall impose no
          adverse effects on downstream properties or receiving water bodies and that the conveyance of
          flows will be in a safe manner with minimal risk of human endangerment as well as the following
          objectives:

            Address the need for stormwater quantity control measures.

            Ensure there is no actional impacts from the subject site for events up to and including the 1% AEP
            event.

            Ensure proposed quantity control measures detain and convey flows in accordance with QUDM
            (2017) minimum freeboard recommendations.

 5.1     Proposed Development and Associated Issues
          In this development, the developable site area leads to negligible increase in peak flows downstream
          of the subject site and is located close to the downstream waterway being Weyba Creek, hence in
          the lower portion of the regional catchment. It is anticipated that the bio-retention drainage system
          will allow for infiltration on-site of the additional flows which will permeate into the sub-surface strata,
          hence it is considered unnecessary to include provision for stormwater quantity management.


 6        STORMWATER QUALITY ASSESSMENT
 6.1      Treatment Objectives
          This assessment identifies issues relating to stormwater quality runoff and assesses possible
          methods of treatment if required. The aim of this section of the report is to determine practical
          approaches for achieving improvements in the quality of the stormwater run-off from the site that can
          be readily implemented.

          The SPP 2017 proposes criteria which apply to ‘high-risk’ development for stormwater. The criteria
          include one or more of the following:

             A Material Change of Use (MCU) for an urban purpose which involves greater than 2,500m2 of
             land that:

             will result in an impervious area greater than 25% of the net developable area; or

             will result in six (6) or more dwellings

             A Reconfiguration of a Lot (ROL) for urban purposes that involves a land area greater than
             2,500m2 and will result in six (6) or more lots; or

             Operational works for urban purposes that involve disturbing more than 2,500m2 of land.

          The proposal includes an MCU for a land area of 2,500m 2 that will result in impervious area greater
          than 25% of the developable area. Hence, the development is classed as ‘high risk’ for water quality
          and the SPP 2017 applies.

          The SPP 2017 suggests the development aims to:

             Avoid or otherwise minimises adverse impacts on the environmental values of receiving waters,
             arising from:

BRISBANE / DARWIN / GOLD COAST / HOBART / MELBOURNE / PERTH / SUNSHINE COAST / SYDNEY / TOOWOOMBA             Page 12