Appendix G - Stormwater Management Report

RPS Project Management c/- Lutheran Services                                                          Page 5 of 10
PF80 - Cooroy Care Farm
28 May 2018                                                                                     Ref. No. 2017.0616




Table 2       Water Quality Pollutant Targets

 Indicator                               Objective

Total Suspended Solids (TSS)            80% reduction in average annual load of pollutants leaving the
                                        developed unmitigated scenario compared to the developed mitigated
                                        scenario

Total Phosphorus (TP)                   60% reduction in average annual load of pollutants leaving the
                                        developed unmitigated scenario, compared to the developed mitigated
                                        scenario

Total Nitrogen (TN)                     45% reduction in average annual load of pollutants leaving the
                                        developed unmitigated scenario, compared to the developed mitigated
                                        scenario

Gross Pollutant                         90% reduction in average annual load of pollutants leaving the
                                        developed unmitigated scenario, compared to the developed mitigated
                                        scenario


Based on the Deemed to Comply solutions in the State Planning Policy the total area designated for
vegetated stormwater treatment devices would be in the order of 1.5% of the 7.5ha development
(approx. 1,125sqm), although this figure is likely to be considerably reduced through the utilisation the
strategies listed above.

        3.4           Stormwater Harvesting
Stormwater harvesting is anticipated to occur through the use of rainwater tanks and the existing dam.

Rainwater tanks will provide the majority of potable water requirements for the site and the existing dam
is expected to meet the non-potable water needs. The catchment to the existing dam is approximately
1.7ha. Refer to Appendix D for catchment details.

For further details refer to the engineering services report titled, “PF80- Cooroy Care Farm, Water
Supply & Wastewater Servicing dated 25th October 2017”.



        3.5           Bruce Highway Hydraulic Analysis
The Bruce Highway Hydraulic Analysis Report (September 2010) prepared for Department of Transport
and Main Roads by GHD indicates that the Bruce Highway overtops in larger rainfall event with the
possibility to restrict access to the site in the Probable Maximum Precipitation Design Flood (PMPDF).
The key findings of the report relevant to our site are as follows:
    •     The Bruce Highway road shoulder (RL 117.5) will likely overtop to a depth of approximately
          0.6m ( RL 118.07) in the Extreme Event (Probable Maximum Precipitation Design Flood
          PMPDF)
    •     The properties above the highway (along Blueberry Drive) are likely flood affected at RL 113-
          115. There is no mention of downstream properties being affected in the report.
    •     No overtopping of the highway is noted in storms up to the 100yr ARI storms (RL 112.13 max.
          i.e. 5m freeboard below the road shoulder)
    •     There is access in a north direction along the Bruce Highway in all events.

A copy of the GHD Hydraulic Analysis can be provided on request.