MCU14/0106 & OPW15/0001 Information Request Response Report (absent appendices)

                                                                                                      Noosa Civic Expansion
                        28 Eenie Creek Road, Noosaville and parts of the road reserves of Hofmann Drive and Walter Hay Drive




5           Hydrology
5.1         Water Quality
            “The layout and quantum of bio-basins need to be confirmed via a refined MUSIC model that
            reflects the site layout, rather than the broad simplified approach taken in the SWP.

            Information Required:
            50   Revised MUSIC modelling to demonstrate the proposed stormwater quality
                 objectives can be achieved for the proposed development layout. In particular, the
                 following needs to be addressed:
                 (a) Catchment Set-up - The MUSIC model has used 1 catchment only whereas the
                     developed scenario will have several catchments draining to a least 4 different
                     areas.
                 (b) Rainfall Set-up - The MUSIC model does not appear to have used the Cooroy
                     Composite Station
                 (c) 40059 for the model (i.e. 1973 -1983) as stated in the report and as per the
                     guidelines. The model should be revised to incorporate this station.
                 (d) Bioretention Basins: As the basins will be used for flood attenuation, the basins
                     should be checked to ensure velocities are kept below the Water By Design’s
                     “WSUD Technical Design Guidelines for SEQ” Velocities should be in the range
                     of 0.5m/s for minor floods (2-10yr ARI) & 2.0m/s for Major Floods (50-100yr ARI)
                     + plus risk assessment of erosion potential.”
            RESPONSE
            The MUSIC model for the proposed development has been updated to reflect a multiple outlet
            configuration, as requested. Please refer to Appendix E – Stormwater Management Plan for
            details. Rainfall data has been confirmed as being consistent with the reporting and guidelines.
            Cardno advises that bio-retention basins are not at risk of erosion from flooding because they
            are not being used for flood attenuation. Car park bio-retention basins are being used for ponding
            only and will not have direct in-flows. Consequently adverse velocities are not expected in these
            areas.

5.2         Water Quality
            “The submitted MUSIC model does not appear to consider the impacts of waters from
            catchments F1, G1 and H on the overall stormwater quality.

            Information Required:
            51   Demonstrate how waters from these catchments will be considered in the MUSIC
                 model and consistent with the proposed design.”
            RESPONSE
            Please refer to Appendix E – Stormwater Management Plan in response to Item 51.
            Cardno advises that the small amounts of additional roads and hardstand within catchments F1
            and G1 will be treated by the vegetated corridor for treatment in the corridor vegetation.
            Catchment H will ultimately be developed and include its own treatment measures. Until that
            occurs, the only developed portion of the catchment will be road runoff, drained to the bio-basin
            proposed in the centre of the roundabout. An interim diversion bund will direct the runoff from
            catchment H past the proposed bio-basin.



June 2015                                           Cardno HRP                                                           31