16-001014-01A (Swmp)

4         STORMWATER QUALITY
It is expected that the proposed development will increase the export of pollutants in runoff from the subject site. A
treatment train of a suitable Stormwater Quality Improvement Devices (SQID’s) have been proposed to intercept and
capture the pollutants. The methodology adopted in this analysis is generally consistent with the past approvals.
However, the proposed Water Quality Control Pond has conservatively not been modelled. This section discusses:

    The identification of key stormwater pollutants associated with the proposed development;
    The Water Quality Objectives (WQO’s) identified for the catchment;
    The stormwater quality management strategy to mitigate the increase in pollutant export; and
    The modelling of the proposed measures and comparison to the identified WQOs.

4.1       POLLUTANTS OF CONCERN
Typical key pollutants expected to be generated during the operational (post-construction) phase of the planned
development are listed as follows, with those presented in capitals being the key pollutants to be targeted for treatment:

     LITTER                                                    HEAVY METALS (associated with fine sediments)
     SEDIMENT                                                  Surfactants
     Oxygen demanding substances (possibly present)            Organochlorines & organophosphates
     NUTRIENTS (N & P)                                         Thermal pollution
     Pathogens / Faecal coliforms                              pH altering substances
     Hydrocarbons
Only the key pollutants will be further addressed in this report; however, the treatment train developed will adequately
mitigate the other pollutant loads. As heavy metals will predominately be associated with fine sediment, controls
proposed to reduce total suspended solids will also adequately reduce loads of heavy metals.

4.2       WATER QUALITY OBJECTIVES
Healthy Waterways WSUD Technical Guidelines (2006) outlines stormwater pollutant load reduction objectives required
for all developments within South East Queensland. These objectives have been adopted as the WQOs for conceptual
modelling of the development site and are summarised in Table 4-1 below.

                                  Table 4-1:   Load Reduction Water Quality Objectives
                            Total Suspended         Total Phosphorus                                  Gross Pollutants
        Pollutant                                                           Total Nitrogen (TN)
                              Solids (TSS)                 (TP)                                            (GP)
     Load Reduction
                                   80%                     60%                      45%                      90%
         Target

It should be noted that the above load-based objectives are consistent with those specified in the SEQ Regional Plan
Guideline No. 7, required under the SPP 2014.

4.3       STORMWATER QUALITY MANAGEMENT STRATEGY
A treatment train of suitable SQIDs has been proposed to mitigate the potential increase of stormwater pollutant loads.
Three SQIDs have been provided for the development to treat stormwater runoff before discharging downstream. The
locations of these devices are shown on Drawing No. B14158.W-SK102 in Appendix G.

As presented in Drawing No. B14158.W-SK102 in Appendix G some minor external catchment runoff flows through the
site and will be treated by the SQIDs. Treatment of stormwater runoff from external catchment areas of the railway
corridor and Cooroy Connection Road adjacent to the site is not an obligation of the developer. Not treating these



16-001014-01 | STORMWATER MANAGEMENT PLAN (SWMP)                 COOROY RETIREMENT COMMUNITY, TRADING POST
| PALM LAKE RESORTS                                                                          ROAD, COOROY                  | 15