Reference Document - Flood & Stormwater Management Plan 28_8_2025

                 Figure 3-2: MUSIC Model Layout



                 3.3.       Treatment Measures
                 Runoff from the development will be treated through a bioretention basins. The locality of the treatment
                 devices servicing the development is shown in Figure 3-1.

                 3.3.1.     Bioretention System




                 Bioretention systems use ponding above a treatment surface to maximise the volume of runoff flowing
                 through the filtration media. They typically convey flows above the design event through overflow pits or a
                 weir. The treatment system operates by firstly filtering surface flows through surface vegetation and then
                 percolating runoff through prescribed filtration media. This media provides treatment through fine
                 filtration, extended detention and biological uptake of nutrients.

                 As these systems take approximately 12-24hrs to drain, the maximum depth of pondage allowed to occur
                 over the filter area has been limited to 300mm, with a minimum filter media depth of 500mm. Table 3-5
                 summarises the proposed design parameters for the main bioretention system for this development, and
                 highlights the size of the existing bioretention basin approved as part of 25 Pavilion Street, along with the
                 upgraded size to account for the additional development from 33 Pavilion Street . As noted above this may
                 be split into several devices on detailed design. It is to be noted that the Orthophosphate content of the
                 filter media has been reduced to 30mg/kg in line with recent advice from Healthy Waterways.




                 23-0167SMP01-V4 | Stormwater Management Plan | 33 Pavilion Street, Pomona                            Page 32

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