16-001014-02A (Ultimate SCMMP)

It is also noted that the Bioretention Device will not be a Council asset. Hence, it will be the responsibility of the developer
to manage and replant the basin in the very unlikely event that extreme oil spillages damage the Bioretention Devices
vegetation.

Apart from the Northern Bioretention Basin, GPT’s are proposed upstream of all Bioretention Devices and subsequently
the proposed pond. As discussed below and GPT’s have the capability of trapping floating oil and grease pollutants and
are considered to be an appropriate pre-treatment to Bioretention Devices, albeit conservative where the catchment is
small. Since Catchment A is only 2.45ha with no significant areas of car parking a sediment forebay is to be provided.
Note that the Northern Bioretention Basin does not discharge into the proposed pond.

The HumeGard GPT proposed upstream of the proposed Bioretention Devices has the capability of trapping floating oil
and grease pollutants. As demonstrated on Page 2 of the HumeGard GPT Technical Manual provided in Appendix C,
the application of a floating boom provides separation at the surface of the waters between the sediment storage
chamber and the outlet chamber. This effectively captures pollutants such as oils and greases that float to the surface.
Based on laboratory and field testing, Table 1 on Page 3 of the Technical Manual indicates 90% removal efficiency of
Hydrocarbons during emergency spill events.



3.2       CONSTRUCTION PHASE / ESTABLISHMENT
Outlined below are the proposed procedures and methodology for the construction and operational establishment of the
proposed Bioretention Devices throughout the site. Procedure and methodology has been based on Water By Design’s,
Construction, and Establishment Guidelines: Swales, Bioretention Devices, and Wetlands (2010) and Healthy Waterways
WSUD Technical Design Guidelines for South East Queensland (2006).

Construction of the Retirement Community and the building works has the potential to mobilise large quantities of
sediment in runoff. For the Bioretention Devices to perform as designed there is a need to protect filter media and basin
vegetation during this phase of the development. Therefore a staged construction and establishment method for
construction of the Bioretention Devices will be followed.

It is proposed to follow an installation procedure for each Bioretention Devices generally in accordance with Option 1 of
the Staged Construction and Establishment Methodology as outlined in Table 3.6 and Section 3.8.1 of the Water by
Design Construction and Establishment Guidelines (2011). A summary of this methodology is presented below.

1)   Civil Works Functional Installation – Initially the basin locations will be used as a Sediment Basins or Traps. Once the
     majority of the civil construction works are complete, earthworks and shaping to create the layout and functional
     elements of the Bioretention Devices will be undertaken. This includes installation of functional elements (e.g. inlets,
     outlets structures, subsoil drainage, transition layers and filter media) shall be undertaken as per the methodology
     detailed in Section 3.9.1 in the Water by Design Construction and Establishment Guidelines (2011). The functional
     elements will be protected from construction sediment loads by:
         Sediment fences around the perimeter of the systems.
         Laying a temporary filter cloth (or 25mm thick layer of course sand and 25mm of topsoil) over the Bioretention
          filter. This will be kept in place during the finalisation of Civil Works and the Building Phase.
         Subject to timeframe of building works topsoil can be seeded.

2) Building Phase Construction – During this phase the Bioretention Devices shall continue to operate as Temporary
   Sediment Basins or Traps. Sediment fences shall remain around the perimeter of the systems (both around the filter
   media and the top of batter) to restrict sediment inflow. Clear indications of the restriction of traffic to the Bioretention
   Device shall also be displayed.

3) Landscape / Operational Establishment – When the Building Phase is 80% complete in the upstream catchment, the
   temporary protective measures and accumulated sediments within the systems will be removed. The basin shall be
   planted with vegetation and landscaped in accordance with the approved landscape plans. Sufficient watering and
   removal of weeds following planting shall be undertaken in accordance with Section 3.9.3 of the Water by Design
   Construction and Establishment Guidelines (2011).


16-001014-02A | SMCMP | PALM LAKE RESORTS                           COOROY RETIREMENT COMMUNITY, TRADING POST
                                                                                                ROAD, COOROY                 | 12