Stormwater Management Plan

GOOD SHEPHERD LUTHERAN COLLEGE                                                             ODYSSEY CONSULTING GROUP
Lot 30 on SP170751                                                              Conceptual Stormwater Management Plan
115 Eumundi Noosa Road, Noosaville                                                                    Project No: K4277

5.4.2 Design Parameters of the Stormwater Quality Improvement System
         Detailed design of the stormwater treatment train shall be in accordance with the WSUD, Technical
         Design Guidelines for South East Queensland – Version 1 (June 2006).

         BIO-RETENTION BASINS
         A bio-retention basin is designed to pond stormwater allowing it to percolate through a layer of filter
         media, typically sandy loam. Runoff passing through the filter media is collected with perforated pipe
         discharging to the downstream drainage infrastructure. The Bio-retention basins shall be located to
         treat all stormwater from development area.

         The bio-retention basins have been modelled with the following properties:

                    Filter media                        Sandy Loam;
                                                         5 – 10% Organic Content in              accordance      with
                                                         AS1289.4.1.1;
                                                         Average D50 0.45 mm;
                                                         Ksat 180 mm/hr;
                                                         TN Content = 400 mg/kg
                                                         Orthophosphate Content = 20 mg/kg
                    Filter media depth                  0.40 m;
                    Drainage layer                      0.20 m;
                    Extended detention depth            0.30 m;
                    Seepage                             0 mm/hr;
                                                                     2             2
                    Filter Area                         Basin 1: 20m , Basin 2: 4m ;
                                                                     2             2
                    Surface Area                        Basin 1: 20m , Basin 2: 4m .

         The permeable pavement has been modelled with the following properties:

                    Filter media                        Sandy Loam;
                                                         5 – 10% Organic Content in accordance                   with
                                                         AS1289.4.1.1;
                                                         Average D50 1 mm;
                                                         Ksat 360 mm/hr;
                    Filter media depth                  0.40 m;
                    Extended detention depth            Pavement 1: 0.0 m, Pavement 2: 0.1 m;
                    Seepage                             0 mm/hr;
                                                                         2                   2
                    Filter Area                         Pavement 1: 69m , Pavement 2: 150m ;
                                                                         2                   2
                    Surface Area                        Pavement 1: 69m , Pavement 2: 150m .

5.4.3 Post Development Modelling Results - Mitigated
         The stormwater quality improvement device (SQID) will reduce the amount of sediments and
         nutrients discharging from the proposed residential development. Table 18 illustrates the treatment
         train effectiveness of the proposed SQID’s.

         Table 18:       Treatment Train Effectiveness of Proposed SQID

                     Parameter                Post         Post Mitigated   Reduction (%)     Water Quality Objectives
                     Flow (ML/yr)             6.26              6.21             0.8                       -
                      TSS (kg/yr)             2310              279             87.9                     80%
                      TP (kg/yr)              3.78             0.817            78.4                     60%
                      TN (kg/yr)               13               6.77            48.1                     45%
               Gross Pollutants (kg/yr)        127               0              100                      90%

         The results demonstrate that the proposed SQID meet the intended water quality objectives for flow,
         suspended solids, phosphorous and nitrogen levels.



K4277-0002-D                                         14 February 2019                                     Page 13 of 16