Attachment 1 - RECOR RFI Cover Letter Response_20210216

                                            Qcurrent Basin          Q2100 Basin        Depth               Depth
                       A.E.P                 Depth (m)              Depth (m)       increase (m)        increase (%)
                          63.2% AEP                   0.659                0.778           0.119                15%
                              0.5 EY                  0.863                1.041           0.178                17%
                              0.2 EY                  1.129                1.255           0.126                10%
                            10% AEP                   1.206                1.331           0.125                  9%
                             5% AEP                   1.318                1.429           0.111                  8%
                             2% AEP                   1.391                1.513           0.122                  8%
                             1% AEP                   1.468                1.567           0.099                  6%

            The basin storage details described within the Cardno Stormwater Management Strategy
            provided storage volumes only to 1.41m therefore, the storage curve was extrapolated to
            additional values beyond this, and depth estimates may not be accurate above this. The
            basin will therefore operate within the design parameters for storms up to and including
            the 10% AEP storm event under 2100 conditions. It is noted that the design parameters
            are currently exceeded under the 1% AEP storm, however will be exceeded beyond the
            5% AEP storm under 2100 conditions.

            As the proposed development is only a small portion of the overall subdivision, and a
            significant number of the allotments are already developed or have approved
            development applications without further attenuation, attenuation for this specific site will
            not achieve a notable impact in the future conditions of the attenuation basin and is not
            proposed.

            We believe the revised design as per the attached plans and as described in this letter
            addresses the requirements of the RFI, however should further information be required
            please contact this office.

            Yours faithfully,
            RECOR Pty Ltd


            Authored By
            SIGNATURE




            Benjamin Parry
            Civil Engineer
            BEng (Hons) MIEAust CPEng NER RPEQ (28084)




P +61 7 5211 1003          A 75 Noosa Drive, Noosa Heads Qld 4567          E [email protected]                  recorconsulting.com