Appendix I - Stormwater Management Plan

                 Drawing number 205-002-C13.01 in Appendix D indicates the development site
                 catchment area for which this assessment was undertaken.
                 Analysis of the two scenarios indicates that there is negligible difference between the
                 pre and post development scenarios. A summary of the 10 year ARI analysis for each
                 scenario is provided as outlined below.


        4.4.1      Existing Scenario

                 As outlined in Section 2.1.2, the existing site is predominately grassed with sparse
                 vegetation. As such, a fraction impervious of 0 is applicable and a subsequent C10
                 factor of 0.70 was applied based on Table 4.5.4 of QUDM. The site has an
                 approximate grade of 11% to the north over a distance of approximately 35m. Based
                 on Table 4.6.4 and Figure 4.6 of QUDM, a time of concentration of approximately 10
                 minutes was adopted for the undeveloped scenario (Refer Appendix F).
                 The analysis of the existing scenario utilising the above parameters for the Rational
                 Method determined that the undeveloped site contributes 43 l/s to Gateway Drive for
                 a 10 year ARI rain event. This is shown in Appendix F.


        4.4.2      Proposed Development Scenario

                 The proposed development is for a commercial tyre retailer which corresponds to a
                 fraction impervious of 0.90 in accordance with Table 4.5.1 of QUDM (refer Appendix
                 F). A time of concentration of 5 minutes has been adopted for the developed scenario
                 based on the site being a relatively small catchment area which consists of
                 predominately paved surface. This supports a conservative approach.
                 The analysis of the developed scenario utilising the above parameters for the
                 Rational Method determined that the developed site will capture 69 l/s for a 10 year
                 ARI rain event. Therefore, the internal drainage infrastructure associated with the
                 development will be designed to accommodate a minimum flow of 69 l/s as required
                 in QUDM for commercial developments.
                 The proposed development connection to the existing pipe network is shown on
                 drawing no. 205-002-C10.01, which shows the indicative connection to the pit located
                 on Gateway Drive, northwest of the site.
                 Notwithstanding the above assessment, further detailed design of the internal
                 stormwater system and connection to the existing pipe network will be required to be
                 undertaken as part of the future Operational Works application for the development.
                 Thus, although the analysis indicates an increase of 26 l/s of flow captured onsite as
                 a result of the development, all flows associated with the 10 year ARI will be
                 accommodated by the internal stormwater network system. The additional flow is




Mogpropmanagement Pty Ltd                         Page 10                                   205-002-002R
Stormwater Management Plan
Noosaville Site