Engineering Hydrology Plans (IWMP)

2 Stormwater Quality
2.1 Design Objectives

This report identifies the stormwater quality management objectives for the
operational phase (post-construction phase) of the proposed development.
Construction based stormwater quality management objectives will need to be
addressed as part of operational works documentation.

2.1.1 Typical Pollutants

Typical pollutants generated during the operational phases of a development are
outlined in Table 1. These pollutants are to be addressed in the management of
water quality discharged from a development site. Construction based pollutants
will be managed through appropriate erosion and sediment control measures.

Table 1: Pollutants typically generated during the operational phase

Pollutant                             Potential Source
                                      Construction packaging, construction waste materials,
Litter
                                      paper, food packaging
Sediment                              Exposed soils and stockpiles

Hydrocarbons                          Fuel or oil spillage, equipment leakage

Toxic materials                       Washwaters, cement slurry, paints, cleaning agents
Acid or Alkaline substances           Acid sulphate soils, cement slurry, washwaters
Oxygen demanding substances           Organic or chemical matter
Nutrients                             Nitrogen, phosphorous
Pathogens/Faecal coliforms            Sewage
Heavy metals                          Sediment runoff
Surfactants                           Detergents, cleaning agents


2.1.2 Operational Design Water Quality Objectives
Water quality objectives or performance criteria for the proposed development are
those stipulated in the SRC Planning Scheme Policy No 6 – Operational works
(Section 7). The applicable water quality design objectives for the site are shown in
Table 2 below.
Table 2: Site stormwater quality objectives (operational phase)

         Minimum reductions in mean annual loads from unmitigated development (%)
  Total Suspended        Total Phosphorous          Total Nitrogen          Gross pollutants
    Solids (TSS)                (TP)                     (TN)                   >5 mm
            80                   60                        45                     90




                                                                                               4