13. APP H. Engineering Services Report

4.1.2            Post-Development Stormwater Drainage Objectives
                 Water Sensitive Urban Design (WSUD) aims to minimise the impact of a development on the
                 natural water cycle by reducing the export of pollutants, sediments and nutrients from the site
                 into the natural watercourse. In order to treat the stormwater runoff from the site, various
                 treatment devices can be used throughout the development area and these concepts can be
                 integrated into the overall design of the road layouts, road cross sections, stormwater layouts
                 and water supply reticulation systems. Stormwater from the development will follow a specially
                 designed stormwater quality treatment train prior to discharge from the site, which will ensure
                 compliance with the water quality objectives. Prior to the legal point of discharge, a planted bio-
                 retention filter area is proposed. A separate treatment system is proposed for stormwater runoff
                 from within the petrol bowsers area, which will need to undergo additional treatment before
                 discharge.

                 The stormwater discharge from the proposed development must be maintained in the case of
                 the pre-developed flow rates for all storm events, from Q1 (frequent flow) to Q100 (major
                 events). Appropriate stormwater infrastructure for the developed site is therefore required to
                 ensure that there is no increase in peak discharge flow rates for the downstream properties.

4.1.3            Proposed Stormwater Drainage Infrastructure
                 The proposed development will maintain the existing three legal points of discharge.
                 Infrastructure to cater for both detention/ retention purposes will be included in the overall
                 development.

                 Within Catchment 1, which outlets to Lionel Donovan Drive, a bio-retention filter media area of
                 32 m2 is required to reduce pollutant loadings in accordance with the Water By Design Bio-
                 retention Technical Design Guidelines.

                 Within Catchment 2, which outlets to Eumundi Noosa Road, a bio-retention area of 22 m2 is
                 required to reduce pollutant loadings in accordance with the Water By Design Bio-retention
                 Technical Design Guidelines.

                 Within Catchment 3, which outlets to Walter Hay Drive, a combined bio-retention / detention
                 basin will be included in the northern corner of Lot 31 on SP170751 to detain and treat
                 stormwater flows prior to discharge. This basin will have an area of 144m2, and 72m2 of that will
                 be used for bio-retention purposes.

                 Please refer to Hyder Stormwater Management Plan Report (Report No. F002-AA007501-AAR-
                 01) for further details of the proposed stormwater management strategy.




139 EUMUNDI-NOOSA ROAD & 30 LIONEL DONOVAN DRIVE, NOOSAVILLE
Hyder Consulting Pty Ltd-ABN 76 104 485 289                                                                    Page 5
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