H Swqmp · 132007.2398

                                                                                                  CALIBRE CONSULTING




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) are been proposed to intercept and
capture the pollutants so that the potential impacts on waterways downstream are mitigated. This section discusses:

     The identification of key stormwater pollutants associated with the proposed development;
     The Water Quality Objectives (WQO’s) identified for the catchment;
     Proposed measures to mitigate the increase in pollutant export; and
     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              Solids (TSS)            (TP)                     Total Nitrogen (TN)     (GP)
Load Reduction Target              80%                     60%                      45%                      90%
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 Stormwater Quality Improvement Devices (SQIDs) has been proposed to mitigate the
potential increase of stormwater pollutant loads. Three end-of-line systems have been provided for the development to
treat stormwater runoff before discharging downstream and incorporated into the site’s basins. The locations of these
devices SQIDs are shown on Drawing No. B14158.W-SK05 in Appendix C.

As presented in Drawing No. B14158.W-SK05 some minor external catchment flows through the site and will also be
treated by the end-of-line systems. Treatment of stormwater runoff from external catchment areas of the railway corridor
and Cooroy Connection Road adjacent to the site is not required by Council. Not treating these external areas would be
difficult in practice as they drain through the site and could not practically be diverted around treatment measures. The
opportunity to treat stormwater runoff from these areas has been taken and will benefit the water quality of downstream


B14158.W-01A | COOROY RETIREMENT COMMUNITY| PALM LAKE RESORTS                                                              |5