SWMP Technical Memo Climate Change as submitted with Further Advice response

                                                                              ENGINEERING & PROJECT SERVICES
                                                                                       Sunshine Coast | Brisbane
                                                                               www.recor.au | ABN 89 647 469 707

7. SWMP implications and conclusion
This memorandum is to be read as an addendum to the SWMP dated 24 June 2026. The lawful point of
discharge, catchment strategy, 75 kL main OSD tank, 170 mm and 245 mm discharge controls and DN375
outlet remain as described in SWMP sections 4.5, 4.6 and 7.2. The updated climate scenario supplements
the original Table 4-3 by demonstrating non-worsening under the specific 1% AEP + 20% Council
requirement.
     •    The 1% AEP rainfall-depth series has been increased by 20% in accordance with Noosa PSP6 section
          SC6.7.6(1)(d)(i).
     •    The Type 2 ILSAX soil classification reflects sandy soils while conservatively allowing for fines and
          development compaction.
     •    The external DN375 RCP model grade has been refined to match the lesser proposed grade on
          Drawing C052, Revision C.
     •    The 15 kL online harvesting tank overflows to the 75 kL OSD tank and provides additional upstream
          attenuation and rainwater reuse functionality.
     •    The mitigated climate-adjusted discharge is 0.148 m3/s, which is below the like-for-like pre-
          development discharge of 0.151 m3/s.
     •    The main OSD tank peaks at approximately 74 m3 with no modelled overflow; no increase to the
          nominated 75 kL main tank is required.


8. Reference documents
     •    RECOR, Stormwater Management Plan - 45 Maple Street and 9 Myall Street, Cooroy, P0478-26-001,
          dated 24 June 2026.
     •    RECOR, Cooroy Social Housing Operational Works Drawings, P0478-26-001, Revision C, dated 6
          August 2026, including Drawings C050, C052 and C054.
     •    Bureau of Meteorology, All Design Rainfall Depths for latitude -26.41952122, longitude
          152.9095387, issued 11 June 2026; dedicated climate-adjusted 1% AEP file prepared with a 1.20
          multiplier.
     •    Noosa Plan 2020, Schedule 6 - Planning Scheme Policies, PSP6 Engineering Design Standards,
          SC6.7.6(1)(d)(i), Climate Change.
     •    Watercom DRAINS User Manual, ILSAX hydrological model soil classifications.

Prepared by
Eoin Whitmore | RPEQ 31423 | RECOR Pty Ltd




P0478-26-001 | Cooroy Social Housing | RFI Item 4   Page 6 of 6