SBSMR 20004 Revision D - Response to RFI

5.2 PIPED DRAINAGE SYSTEM – POST DEVELOPMENT

Post development areas adopted are as follows:

Total Catchment as before of 3105m2

It is proposed to use detention tank totaling 48m3 with a 160mm orifice overflow outlet for the
development. Additional detention will be provided by the construction of the bio-basin but
has not been included in the below calculations which will be conservative. The design of the
piped infrastructure and detention system was undertaken using Drains program has been used
with Extended Rational Method.

Drains Output:
                         EY        ARI        Post Development Flows m3/s
                          1         1                    0.038
                        0.2         5                    0.054
                        .11        10                    0.061
                        .05        20                    0.067
                        .02        50                    0.075
                        .01        100                   0.082
                                      Table 3 - Site Post-Development


Comparing the results pre and post development:
     AEP       ARI     Pre Development Flows m3/s                  Post Development Flows m3/s
    0.632       1                  0.037                                      0.038
    0.181       5                  0.067                                      0.054
    0.095       10                 0.083                                      0.061
    0.049       20                 0.098                                      0.067
     0.02       50                 0.124                                      0.075
     0.01      100                 0.142                                      0.082
                                Table 4 - Pre & Post Development Comparison


Flows discharging from the site will be adequately mitigated.




NMA-SBSWMR-20004 Noosa Youngcare                                                                 9