Attachment I - Updated Engineering Report & SWMP

                      Table 6.3.2: Rainfall Runoff Parameters

           Rainfall Threshold mm/day                                        1
                              Pervious Area Properties
            Soil Storage Capacity (mm)                                    500
            Initial Storage (% of Capacity)                                10
            Field Capacity (mm)                                           200
            Infiltration Capacity Coefficient - a                         211
            Infiltration Capacity Exponent - b                            5.0
                              Groundwater Properties
            Initial Depth (mm)                                            50
            Daily Recharge Rate (%)                                       28
            Daily Baseflow (%)                                            27
            Daily Deep Seepage Rate (%)                                   0.0

              The pollutant load concentrations for each source catchment have
              been taken from Table 3.8 of the Water by Design’s – MUSIC Modelling
              Guidelines, Version 1.0 2010 and using the concentrations
              recommended for residential areas.

              The MUSIC Model was run utilising available rainfall data for the
              area, being Cooroy, Station 40059. A 6-minute time step analysis was
              utilised for rainfall data from 1973 to 1983. Mean annual rainfall for
              the area is approximately 1595mm.

              The following impervious fractions for various surface types were
              used in the model.


                    Development Type            Surface Type Impervious Fraction (%)
                                          Road Reserve    Roof/Podium       Ground Level
               Commercial                      75             100                 20




              6.3.3 MUSIC Model Results

              Please refer to attached engineering drawings in Appendix B for
              details of the proposed treatment train. Results of the MUSIC model
              are shown in Table 6.3.3, which identifies a complying scheme can
              be provided with construction of a 28m2 bio retention basin with
              27m2 filter area.


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A6035/21/Engineering Report/30-32 Doonella Street, Tewantin                  Page 7 of 9
May 2021    WM/tk
                                    Alta Projects P/L