Approved plan - Site Based Stormwater Management Plan - Job Ref SC-8407 - Revision B - 24 March 2020

   SC-8407 – 45 Maple Street, Cooroy                                                                   5


Issue                                   Design objectives
Drainage         Temporary drainage     1.         Design life and design storm for temporary drainage works:
control          works                             Disturbed area open for <12 months—1 in 2-year ARI event
                                                   Disturbed area open for 12–24 months—1 in 5-year ARI event
                                                   Disturbed area open for > 24 months—1 in 10-year ARI event
                                        2.          Design capacity excludes minimum 150 mm freeboard
                                        3.          Temporary culvert crossing—minimum 1 in 1-year ARI hydraulic
                                                    capacity
Erosion          Erosion control        1.          Minimise exposure of disturbed soils at any time
control          measures               2.          Divert water run-off from undisturbed areas around disturbed
                                                    areas
                                        3.          Determine the erosion risk rating using local rainfall erosivity,
                                                    rainfall depth, soil-loss rate or other acceptable methods
                                        4.          Implement erosion control methods corresponding to identified
                                                    erosion risk rating
Sediment         Sediment control       1.          Determine appropriate sediment control measures using:
control          measures                          Potential soil loss rate, or
                                                   Monthly erosivity, or
                                                   Average monthly rainfall
                 Design storm for       2.          Collect and drain stormwater from disturbed soils to sediment
                 sediment control                   basin for design storm event:
                 basins                            Design storm for sediment basin sizing is 80th% five-day event
                                                    or similar
                                        3.          Site discharge during sediment basin dewatering:
                 Sediment basin                    TSS < 50 mg/L TSS, and
                 dewatering                        Turbidity not >10% receiving waters turbidity, and
                                                   pH 6.5–8.5
Water            Litter and other       1.          Avoid wind-blown litter; remove gross pollutants
quality          waste, hydrocarbons    2.          Ensure there is no visible oil or grease sheen on released waters
                 and other              3.          Dispose of waste containing contaminants at authorised facilities
                 contaminants
Waterway         Changes to the         For peak flow for the 1-year and 100-year ARI event, use constructed
stability and    natural waterway       sediment basins to attenuate the discharge rate of stormwater from the
flood flow       hydraulics and         site
management       hydrology
                              Table 3.2 - Construction Phase Stormwater Quality Objectives