12. APP G. Stormwater Management Plan

                BIO RETENTION BASINS
                A bio-retention area is a vegetated region where runoff is filtered through a filter media layer
                (e.g. sandy loam) as it percolates downwards to receiving underlying reticulation. Specific
                vegetation is to be incorporated into the landscaping of bio-retention areas which effectively
                reduce nutrient loads. Table 20 in the Water By Design Bioretention Technical Design
                Guidelines provides guidance on selecting appropriate plant species for systems where the
                plants have a functional role in stormwater treatment, such as the aforementioned bio-retention
                basins. The landscape architect is to select plant species from this table for the vegetation of the
                basin. The following plant species are suggested:

                      •    Carex appressa;
                      •    Gahnia sieberiana;
                      •    Lomandra hystrix;
                      •    Pennisetum alopecuroides;
                      •    Callistemon sieberi; and / or
                      •    Leptospermum liversidgei.

                Bio-retention areas are to be incorporated within each of the three catchments in the proposed
                development with both a sediment forebay and planted bio-retention filter area. The sediment
                forebay is to mitigate the accumulation of coarse sediment near the basin inflow, which will
                smother vegetation and reduce infiltration. The bio-retention basin is to be incorporated into the
                base of the stormwater detention structure; the lower 300mm of the basin has been excluded
                from the stormwater detention analysis of the basin and is to be dedicated to extended
                detention, ensuring that sufficient volume from frequent storm events will pond in the basin and
                percolate through the filter media receiving treatment.
                A typical example of a bio-retention area in operation with suitable vegetation is presented in
                Figure 6.1 below. A typical section is also presented in Figure 6.2.




                Figure 6.1: Newly Constructed Bio-Retention Area (Salacia Waters, Paradise Point)




139 Eumundi Noosa Road & 30 Lionel Donovan Drive, Noosaville Service Station and Retail Site—Stormwater
Management Plans
Hyder Consulting Pty Ltd-ABN 76 104 485 289                                                                      11
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