Stormwater Management Plan

                              STORMWATER MANAGEMENT PLAN
Client: Hass Holdings ATF The Quasar Trust                            Location: Taylor Court, Cooroy




                           Treated Area

                                                                     Untreated Area




                                          Figure 3 Catchment Areas

4.0 WATER QUALITY MODELLING ASSESSMENT/APPROACH
4.1 Scenario Methodology

The site was modelled using split catchment source nodes, comprised of roof area, road area and
groundcover nodes. The hardstand area of pavement and play-park has been modelled as
groundcover at 100% impervious. The stormwater treatment proposed for the site consists of one
(1) bioretention basin.

The runoff within the area beneath the service station bowser canopy will be captured by a grated
channel surrounding the area and directed to a holding tank. This will reduce the risk of any
potential runoff containing hydrocarbons entering the stormwater network in the event of a spill.
The holding tank will be monitored and emptied when required, particularly prior to a large rain
event. Roof Runoff from the canopy will be directed to the bioretention basin for treatment.

Refer to Stormwater Quality Management Plan in Appendix B.

4.2 MUSIC Model Parameters

The MUSIC Modelling Guidelines – South East Queensland Version 1.0 (2010) was used to
source base and storm flow concentrations and runoff generation. The model was calibrated using
the Bureau of Meteorology (BOM) data from Cooroy Composite, 1973 - 1983, at a 6-minute time
step. This is in accordance with Water by Design’s MUSIC Modelling Guidelines – South East
Queensland Version 1.0 (2010). All source nodes were set up in accordance with this guideline,
specifically for split catchments. The source nodes were set up as ‘commercial’ due to the site
characteristics being similar to those in a commercial area. No routing of drainage links was
adopted for the purpose of taking a conservative approach. This approach assumes that the flow
through the drainage system takes no time, which over estimates the likely pollutant load.

4.3 Land Use/Source Node Areas.

The proposed development has been treated as one (1) catchment. The catchment has further
been divided into contributing roof, landscaping, hardstand and road area. Refer to Table 3 for
details. A MUSIC model concept map is located in Appendix C.
Covey Associates Pty Ltd                         4                                Project No: 161968
Consulting Engineers                                                                 100415 Rpt Iss A