Reference Document - Flood & Stormwater Management Plan 28_8_2025

                 1.4.       Further Advice 7 November 2023
                 Further advice was received from Noosa Council, dated 7 November 2023, regarding the development
                 application (RAL23/0013). The further advice letter asks for the proposal to comply with the Noosa Plan for
                 stormwater items listed below.

                 Issue - Stormwater Quality
                 It is unclear how compliance with the pollutant load reduction targets has been calculated. The scheme requires
                 an 80%/60%/45% reduction in TSS/TP/TN for the unmitigated development site loads. Since the bioretention
                 device receives flows from areas outside the development, a manual calculation of compliance with this target is
                 required, based on the MUSIC model results.

                 This is achieved by:

                 1.   Extracting the development site (current and original developments) source loads from the model
                 2.   Calculating the required pollutant load removal by multiplying (1) by 80%/60%/45%
                 3.   Comparing the required load removal (kg/yr) to the actual load removal achieved by the device

                 This does not appear to have been done.

                 Response:

                 The SMP demonstrates an 80%/60%/45% reduction in TSS/TP/TN for the unmitigated development site
                 loads according to the scheme as summarized in Table 3-7 and Table 3-8.

                 The information provided in the SMP-V2 has been reformatted as per the above request:

                 1.   The source loads of the current and original developments were extracted from the model (refer
                      Figure 1-3) and are summarized in the “Unmitigated (kg/yr)” column of Table 1-1.
                      Note that there is a minor difference between Figure 1-3 and Table 3-7 as MUSIC is a stochastic model, with
                      randomness resulting in minor changes in results between model runs.
                 2.   The required pollutant load removal (2) was calculated by multiplying (1) by 80%/60%/45%. This
                      information is provided in Table 1-1.
                 3.   The actual load removal (3) achieved by the device exceeds the required load removal (2) and therefore
                      meets the target reductions as per the scheme.




                 23-0167SMP01-V4 | Stormwater Management Plan | 33 Pavilion Street, Pomona                                Page 13

Document Set ID: 24092538
Version: 1, Version Date: 02/09/2025