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


          EXECUTIVE SUMMARY
          ADG Engineers (Aust.) Pty Ltd has been engaged by Aspect Architects to prepare a Site Based
          Stormwater Management Plan (SBSMP) suitable for submission to Noosa Shire Council (NSC) as
          additional information in support of a Development Application for a Material Change of Use for a
          proposed Eco Resort Extension to the current RACV Noosa Resort located at 94-142 Noosa Drive,
          Noosa Heads QLD 4567.

          The proposed development as shown in Aspect Architects plans is for eight (8) double storey eco
          resort style units, raised boardwalk footpath links and associated carparking. The proposed
          application to Council also includes works involving converting an existing pond internal to the RACV
          Noosa Resort site into a new pool. ADG make note that this existing pond does not form part of an
          existing site-based stormwater treatment train nor provides further stormwater detention
          management. The pool works is to form part of separate application submitted to Council for building
          approval.

          The report comprises of stormwater quantity and quality assessments. The quantity assessment is
          undertaken to confirm a ‘non-worsening’ of peak flow discharges from the site and the quality
          assessment is undertaken to determine the required stormwater treatment measures to be
          implemented on site.

          The stormwater quantity objective was to demonstrate that there are no impacts from storm events
          up to and including the 1% AEP storm event. The purpose is to ensure that the existing infrastructure
          and/or downstream properties are not adversely affected. Due to negligible increase in peak flows
          from the subject site and the subject site being located close to the downstream waterway hence in
          the lower portion of the regional catchment, it is considered unnecessary to include provision for
          stormwater quantity management as the proposed runoff is intended to infiltrate into the existing sub-
          surface utilising a ‘pipeless’ bio-retention solution. Coffey Geotechnics provided a geotechnical report
          for the neighbouring ‘Noosa Sanctuary’ project previously. This investigation identified a silty sand
          from an approximate depth of 1.0m below the existing ground surface level. It is recommended that
          a hydraulic conductivity test be performed by an experienced geotechnical engineer at the detailed
          design phase to confirm the soils permeability and infiltration capability.

          Currently no stormwater quality management measures are in place for the Eco Village subject site.
          Stormwater treatment measures are proposed to be implemented on site in accordance with Industry
          Best Practice, WSUD Engineering Guidelines and, Council’s Land Development Guidelines to
          provide stormwater treatment for this site. ADG recommends the use of the following devices to meet
          the water quality objectives identified within the SPP 2017 and Council’s WSUD Planning Scheme
          Policies:

             Combined 40kL Rainwater Tank (Reuse)

             30m2 Bioretention Basin that will permit flows to infiltrate into the subject sites sub-surface.

             First flush device/s to divert initial flows (first 12mm of rainfall or hose-down) to vegetated areas

          To address the Noosa Shire Council’s RFI dated 2nd September 2022, the following has been added
          to this SBSMP:

            The revised eMUSIC model compares the pre and post-development stormwater pollutant
            residual loads in Section 6.6 of this report. ADG advise the post-development pollutant residual
            loads are now below the pre-development stormwater pollutant residual loads and that water is
            intended to infiltrate into the sub-surface strata of the subject site through the drainage layer of
            the proposed bio-retention basin. This results in no increase in gross pollutants, total suspended
            solids, total phosphorus or total nitrogen compared to the pre-development scenario.


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