Information Response_010616 · MCU15/0122

                                                                      MORGAN CONSULTING
                                                                     E NGINEERS P TY LTD
                                                                                  15099/RP
                                                                                      Page 2



           sensitivity analysis was undertaken to determine the bioretention area necessary
           to meet the Total Phosphorus water quality objective of less than 16 micrograms
           per litre. It was determined that the water quality objective could not be
           achieved by bioretention basins of any size. Therefore, it is assumed that
           compliance with the State Planning Policy Total Phosphorus water quality
           objective is in this instance acceptable.
Item 14:   Demonstrate the design of proposed bioretention basins provides adequate
           footprint to facilitate for 1:4 batters.
Response: All batters within the proposed bioretention basins will have 1:4 batters. Refer
          to the Site Based Stormwater Management Plan (revision 3) prepared by Morgan
          Consulting Engineers for details.
Item 15:   Where proprietary devices are proposed as an option- demonstrate that the
           methodology for pollutant reduction modelling for the proprietary device is fully
           endorsed by Stormwater Australia for their pollutant reduction efficiencies,
           consistent with the Water by Design MUSIC modelling guidelines, and that the
           applicant is satisfied with the maintenance costs likely to be involved with
           maintaining the water quality treatment train to perform as modelled.
Response: Refer to the attached documentation from Humes Water Solutions which
          demonstrates that the methodology for the pollutant reduction pollutant
          modelling is consistent with the Water By Design MUSIC modelling guidelines.
          Additionally, the documentation demonstrates compliance with the Draft
          Stormwater Australia – Stormwater Quality Improvement Device Evaluation
          Protocol.
Item 16:   Provide the MUSIC modelling files used to size and design the proposed water
           quality treatment train.
Response: Attached are the two MUSIC Modelling Files for the two stormwater quality
          treatment options referenced in the Site Based Stormwater Management Plan
          (revision 3) prepared by Morgan Consulting Engineers.
Item 17:   Provide a preliminary drainage plan to demonstrate that drainage from the
           proposed water quality treatment train can be achieved.
Response: Refer to MCE drawings 15099/SK02/A1, 15099/SK03/A0 and 15099/SK04/A1
          included in the attached Site Based Stormwater Management Plan (revision 3)
          prepared by Morgan Consulting Engineers.
Item 18:   Demonstrate the proposed water quality treatment train will not increase the
           amount of excavations needed into Acid Sulphate Soils and will not be subject to
           groundwater influence.
Response: It is noted that the entire basement of the proposed development will be
          situated below 5m AHD. Accordingly, an Acid Sulfate Soils Assessment will be
          provided. Should Acid Sulfate Soils be encountered on-site, they will be managed
          in accordance with an Acid Sulfate Soils Management Plan to be implemented
          during construction. It is noted that the site is within close proximity to Lake
          Doonella which is tidal and therefore maintains a varying water surface level
          around 0.00m AHD. Therefore, it is understood that the groundwater (if present)
          level on-site would be at 0.00m AHD or very close to 0.00m AHD. The proposed
          water quality treatment measures will have a minimum relative level of
          approximately 3.0m AHD. Therefore, groundwater influence is not considered to
          be possible.