Minor Change Report MCU24 0142 01 & OPW24-0185.01 (As Published)

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               2.     BACKGROUND
               A development approval for a Material Change of Use – Multiple dwelling (3 Units) and a
               development approval for Operational Works – Earthworks, Stormwater and Landscaping were
               approved on 23 June 2025.
               To assist with the assessment of this application Council enlisted the services of Switchback
               Consulting to review the submitted stormwater management system.
               3.     ASSESSMENT
               3.1. Instruments for Statutory Assessment
               Under the Planning Act 2016 the application must be assessed against each of the following
               statutory planning instruments to the extent they are relevant to the development:
               •      State Planning Policy;
               •      South East Queensland Regional Plan;
               •      Planning Regulation 2017; and
               •      Noosa Plan 2020 (25 September 2020).
               3.2. Statutory Process
               The applicant has requested to make a minor change to a development approval under s78 of the
               Planning Act 2016. An application for a minor change to a development approval can only be made
               in circumstances where a change would constitute a ‘minor change’.
               The proposed change to the development approval requested by the applicant is determined to
               constitute a minor change on the grounds that:
               •      the development would not result in substantially different development as the proposal does
                      not:
                      o     involve a new use; or
                      o     result in the application applying to a new parcel of land; or
                      o     dramatically change the built form in terms of scale, bulk and appearance; or
                      o     change the ability of the proposed development to operate as intended; or
                      o     remove a component that is integral to the operation of the development; or
                      o     significantly impact on traffic flow and the transport network, such as increasing traffic
                            to the site; or
                      o     introduce new impacts or increase the severity of known impacts; or
                      o     remove an incentive or offset component that would have balanced a negative impact
                            of the development; or
                      o     impact on infrastructure provisions.
               •      the change does not include prohibited development;
               •      the change would not require the application to be referred to an additional referral agency
                      or cause a referral agency to have regard to new matters prescribed by regulation;
               •      where the original application was code assessable, the change would not cause the
                      application to become impact assessable.
               3.3. Statutory Instruments – Planning Scheme
               The original application was lodged and assessed under the now superseded Noosa Plan 2020
               (25 September 2020). Pursuant to s81 of the Planning Act 2017, Council must consider the
               planning scheme in effect when the original development application was lodged, however Council
               may give weight to Noosa Plan 2020 (26 September 2025) as the planning scheme in effect at the
               time of the minor change application being lodged. It is noted that there has been no change to the
               relevant benchmarks of the current Noosa Plan 2020 (Amendment 2 – 26 September 2025.
               The following codes from Noosa Plan 2020 are applicable to this development:
               •      Medium Density Residential Zone Code;
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               •        Noosaville Local Plan Code;
               •        Dual Occupancy and Multiple Dwelling Code;
               •        Works Codes;
               •        Acid Sulfate Soils Overlay Code
               •        Flooding and Inundation Overlay Code.


               Existing Conditions 38 and 66 (Operational Works Approval)
               The applicant has requested that conditions 38 and 66 be amended to reference an amended
               Stormwater Management Report which proposes a revised detention system.
               Approved Stormwater Management System
               The approved system proposed to collect stormwater via a series of pits and pipes and attenuate
               flows in a 10m3 detention tank before discharging into Robert Street via the existing kerb
               adapter(s).
               The rationale for providing detention in the first instance is unusual. The stormwater detention
               calculations incorrectly assumed a lower fraction impervious (0.4) than what currently exists on
               site (~0.8). Additionally, the developed fraction impervious (1.0) was assumed higher than
               expected through the use (~0.9). In combination, these calculations overstate the increase in
               development flows to a point where detention could reasonably be avoided.
               The size of the low-flow orifice (30mm) is unusually small and limited to a maximum flow rate of
               ~1.7 L/s. For context, the SWMP reports that during very frequent, frequent, and infrequent events
               the development will produce peak flow rates of 27 L/s, 59 L/s and 103 L/s, respectively. The net
               result is likely that the detention tank will rapidly fill during the frequent and infrequent events and
               engage the high overflow weir, meaning in events other than very frequent event, peak storm flows
               will not be attenuated and coincide with peak storm flows external to the site, meaning the detention
               system will be ineffective. Further, it is likely the inefficiency of the outlet structure will result in
               system blockages noting now blockage screen as been provided in accordance with AS3500.
               Amended Stormwater Management System
               The amended system removes the 10m3 detention tank and instead relies on 142 metres of 300mm
               dia. uPVC to attenuate flows via the outlet structure and discharge into Robert Street. The pipes
               connect through a series of manholes and run two-to-three pipes in parallel.
               Assessment of Request
               A Request for Further Advice was issued seeking more information on some of the areas of non-
               compliance (fall, ability to empty between events, parallel pipes, roofwater connections,
               maintenance access, impacts on Robert Street, etc.) and advised the applicant the system was
               unnecessarily complex, unlikely to function and unlikely to be supported.
               The response and overall review of the system as referred to Council’s external stormwater
               consultant who provided the following comments:
                    •    None of the above-mentioned issues with the sizing and design methodology have been
                         addressed.
                    •    The calculations in the SWMP include a 177mm orifice being used in the calculations even
                         though a 30mm orifice is retained in the design.
                    •    There is only 400mm level difference between the overflow weir in the control pit and the
                         surface levels at the most upstream pits. No HGL calculations are provided, and it seems
                         reasonably likely that surcharge of these pits will occur in moderate rainfall events.
                    •    There are a number of pipe connections and changes of direction that seem to indicate
                         they would be done by gluing PVC pipe to couplings. Normal practice for surface
                         stormwater systems is that pits would be provided at these types of junctions (refer
                         AS3500.3).
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               In summary, the proposed changes to the stormwater management system do not comply with
               industry standards. It has been determined that the system would be ineffective at providing
               attenuation and may adversely affect the site’s ability to drain effectively. The level of information
               and methodology provided is inadequate. It is recommended that the applicant consider
               removing the detention system entirely and rely on a pit-and-pipe solution and the grading of the
               site to effectively drain the development.
               The change application is not supported and recommended for refusal.
               Recommendation
               It is recommended existing conditions 38 and 66 remain unchanged, as the change application
               has been recommended for refusal.


               4.     CONSULTATION
               4.1. Referral Agencies
               Not applicable
               4.2. Internal Council Referrals
               The application was forwarded to the following internal Council officers for review and/or comment:
               •      Senior Development Engineer, Development Assessment
               5.     CONCLUSION & REASONS FOR DECISION
               The proposed request to change the stormwater management conditions 38 and 66 is not
               supported as the changes do not comply with industry standards. The application is therefore
               recommended for refusal.
               The report is provided in accordance with Section 83(9) of the Planning Act 2016.
               RECOMMENDATION
               With regard to Application No. MCU24/0142.01 to make a minor change to an existing approval
               for Material Change of Use – Multiple Dwelling (3 Units) and Operational Works – Earthworks,
               Stormwater and Landscaping situated at 11 Robert St Noosaville Qld 4566 and described as Lot
               1 on RP168283, Council on 5 March 2026 decided to:
               Refuse to make the change to conditions 38 and 66 (Operational Works ) for the following reasons:
               1.     The proposed change application fails to comply with Acceptable Outcomes 2.1, 2.3 and
                      corresponding Performance Outcome 2 of the Water Quality and Drainage Code. As a result,
                      the development does not demonstrate that stormwater quantity and quality will be managed
                      to avoid adverse impacts on adjoining properties or the broader drainage network.
               2.     The amended internal stormwater drainage infrastructure has not been designed in
                      accordance with Planning Scheme Policy 6 Engineering Design Standards and the
                      Queensland Urban Design Manual (QUDM) which is likely to result in the development being
                      inadequately drained creating an unacceptable risk of nuisance and ponding.
               3.     The detention calculations have not been undertaken in accordance with any contemporary
                      recognised hydrologic sizing method and is unlikely to satisfy QUDM or AS3500. The limited
                      technical information provided suggests that detention is not required for this site and that
                      the system is likely to worsen the post-development drainage characteristics of the site.




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Document Set ID: 24562651
Version: 8, Version Date: 06/03/2026