Response to Information Request - REC13/0015

                                                                                         ~
                                                                                      Callaghan & Toth

     1.   Bioretention Basin has been placed in a proposed Drainage Reserve adjacent to Lake
          MacDonald Drive. One (1)bio-retention basin is proposed with an area of 25m2. It has
                 layer depth of 0.5m and an extended detention depth of 0.3m. The size and
          a filter

          depth of the systems have been designed in accordance with Figure 4.2. The bio-
          retention basin drains to a gully within the site.



4.2.3     Rainfall Data


The meteorological data used for the MUSIC Model was the data for Cooroy from 01/01/92-
31/12/01. The choice of the data was based on the mean annual rainfall for Cooroy being
similar to the mean annual rainfall for Lake MacDonald Drive:


The mean Annual Rainfall for Cooroy                        92   -
                                                                    02 = 1585mm


The MUSIC Modelling Guidelines for South East Queensland               -
                                                                         Version 1 December 2010
details that Cooroy data for 1973 to 1983 should be used. This data has an annual average
Rainfall of 1600mm. It is considered that the 10 year period from 1992 2002 has a relatively
                                                                                  -




close mean annual Rainfall to the recommended 10 year period and as such is acceptable to
use in this case.



4.3       MUSIC Modelling Results


The MUSIC modelling program has been used to investigate the performance of various
treatment options in the treatment train. MUSIC Version 5 is capable of incorporating rainwater
re-use in the model. These features have been used         in making comparisons between different
stormwater management systems for this report.


4.3.1     Water Quality Objectives


This model meets the pollution load reduction target as detailed in Water by Design Deemed to
Comply Solutions Storm water Quality Management (South East Queensland) version 1.0-
                           -




Table A-2. The following have been included in Appendix 2.


          .      The treatment train effectiveness for the system.


          .      The MUSIC Version 5 Summary Report.


The information above indicates that the new lots will achieve reductions in pollutant loads as
detailed in Table 4.2 below.


          TABLE 4.2:              COMPARISON OF LOAD REDUCTIONS


              Parameter                           MUSIC                POLLUTANT
                                              REDUCTION                    LOAD
                                                RESULT                 REDUCTION
                                                                        TARGETS
              Flow                                 1.4%
              Total Suspended Solids              94.7%                    80%
              Total Phosphorous                   73.6%                    60%
              Total Nitrogen                      60.9%                    45%




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55 Lake MacDonalld Drive   -

                               Stage 1      SMP Revl.doc                              May 2013   1225