Stormwater Management Plan

Good Shepherd Lutheran College                                                               Odyssey Consulting Group
Proposed Unit Development                                                     Conceptual Stormwater Management Plan
Lot 30 on SP170751                                                                                  Project No: K4277
115 EUMUNDI NOOSA ROAD, NOOSAVILLE

                                                                                                      3
        The hydraulic analysis using the DRAINS model has determined that a minimum of 126 m of storage
        is required for runoff attenuation and is to be provided in the form of a detention tank located within
        the open space area. Refer to Odyssey Consulting Group, Stormwater Management Plan (Ref:
        K4277/P007/A) and Odyssey Consulting Group, Stormwater Detention and Bio retention Details (Ref:
        K4277/P010/A) included as Appendix F, for details of the tank arrangement, indicative location and
        preliminary stormwater layout. The final location onsite and construction levels will be determined at
        detailed design stage.

        A copy of the DRAINS model used in this report can be made available to Council upon request.



5.0 WATER QUALITY ASSESSMENT
5.1     Background
        The development of land has the potential to increase the pollutant loads within stormwater runoff
        and downstream watercourses.

        During the construction phase of the development disturbance to the vegetation on the site has the
        potential to significantly increase sediment loads entering downstream watercourses. The operational
        phase of the development will increase the density of residential land use potentially increasing the
        amount of sediments and nutrients washing from the site.

        The following sections describe the predicted increase in pollutant loads generated by the proposed
        development and treatment devices to mitigate the potential increases. In accordance with industry
        guidelines suspended solids, nitrogen and phosphorus will be targeted for reduction during the
        operational phase of the development.

5.2     Water Quality Objectives
        To protect the water quality of the downstream watercourses the following water quality objective
        has been applied to stormwater runoff from the site in accordance with State Planning Policy. The
        following load reduction targets must be achieved when assessing the post-developed sites treatment
        train (comparison of unmitigated developed case versus developed mitigated case):
            80% reduction in Total Suspended Sediment (TSS);
            45% reduction in Total Nitrogen (TN);
            60% reduction in Total Phosphorus (TP); and
            90% reduction in litter (sized 5 mm or greater)

5.3     Construction Phase
        A high risk of stormwater pollution will occur from the site during the construction phase due to
        erosion and sediment transportation off site to the receiving environment. The majority of this risk
        results from construction activities disturbing the site and exposing areas of soil to the direct erosive
        influence of the environment. The following section outlines the procedures necessary to minimise
        erosion and control sediment during construction in accordance with Department of Environment and
        Resource Management’s, Urban Stormwater Quality Planning Guidelines, 2010, (DERM USQG). and
        the Institution of Engineers Australia (QLD) Erosion and Sediment Control Guidelines.

5.3.1   Common Pollutants
        In accordance with Table 1.1 (DERM USQG, 2010) the following common pollutants have been
        identified for the Construction Phase of this development.




K4277-0002                                        14 March 2018                                           Page 10 of 16