RFI - Attachment 4 - Updated Stormwater Management Plan

                                       STORMWATER MANAGEMENT PLAN
Client: Devcon Capital 9                                                  Location: 11 Leo Alley Road, Noosaville


3.0 STORMWATER QUALITY MANAGEMENT

3.1 Water Quality Objectives

This section of this SMP will demonstrate how the proposed stormwater quality management
strategy complies with the requirements of NSC and the SPP (2017) in terms of demonstrating how
the relevant stormwater pollutant reduction objectives will be met.

Stormwater runoff generated from the site must achieve the required pollutant reduction targets
(Table 1) and be demonstrated through the use of appropriate modelling software.

                       Table 1 – Pollutant Reduction Targets for South East Queensland
           Pollutant Type                                    Reduction Objective
   Total Suspended Solids (TSS)              80% reduction in average annual load of pollutants
      Total Phosphorus (TP)                  60% reduction in average annual load of pollutants
         Total Nitrogen (TN)                 45% reduction in average annual load of pollutants
       Gross Pollutants (GP)                 90% reduction in average annual load of pollutants

The proposed development ultimately drains to the Noosa River located approximately 1.9 km to the
north of the site. Table 2 outlines the specific performance criteria required within receiving waters
for the Noosa River, as identified in the Environmental Values and Water Quality Objectives – Basin
No. 140 (Part), including Kin Kin Creek, Teewah coastal creeks, Lakes Cooroibah, Cootharaba,
Doonella and Weyba (Environmental Pretection Water Policy, 2010). The proposed development is
identified on Plan WQ1413 of the Environmental Protection (Water) Policy (2009) Southeast
Queensland Map Series as being coastal freshwaters.
 Table 2 – Noosa River Environmental Values and Water Quality Objectives (as per WQO’s for coastal
                                           freshwaters)
                           Pollutant                             Water Quality Objectives
                       Turbidity                                         <10 NTU
                Suspended Solids (SS)                                     <6 mg/L
                     Chlorophyll a                                         <5 µg/l
                    Total Nitrogen                                       <500 µg/L
                  Oxidised Nitrogen                                      <60 µg/L
                  Ammonia Nitrogen                                       <20 µg/L
                  Inorganic Nitrogen                                     <420 µg/L
                   Total Phosphorus                                      <50 µg/L
           Filterable Reactive Phosphorus                                <20 µg/L
           Dissolved Oxygen (% saturation)                         85 – 110 % saturation
                          pH                                              6.5 – 8.0
                     Conductivity                                       500 µS/cm

3.2 Water Quality Modelling

3.2.1 MUSIC Model Parameters
The MUSIC Modelling Guidelines – South East Queensland Version 1.0 (2010) was used to source
base and storm flow concentrations and runoff generation. The model used rainfall data from the
Bureau of Meteorology (BoM) Cooroy Rainfall Station, over a ten (10) year period (1973 – 1983) at
a 6 minute time step. This adopted rainfall station and period is in accordance with Water by Design’s
MUSIC Modelling Guidelines – South East Queensland Version 1.0 (2010). All source nodes were
set up in accordance with this guideline, specifically for split catchments. Commercial and industrial
rainfall-runoff parameters and industrial pollutant export parameters have been used for each split


Covey Associates Pty Ltd                                2                                  Project No: 192297
Consulting Engineers                                                                         26719Rpt, Issue E