Att 8 - SWMP

             2. Stormwater Quality
             A conceptual site drainage design has been prepared and is shown in Figure 2.1. The
             detailed design will be completed with a future OPW application, with this conceptual design
             is intended to show how the site could be drained and integrated with stormwater quality
             treatment devices. The key aspects of this drainage design are:

                      External piped drainage from Ernest Street is incorporated/collected in the
                       underground site drainage system and connects to the trunk drainage in Hilton
                       Terrace
                      The site is divided into 2 catchments – with Catchment A drainage to the West and
                       Catchment B to the East
                      Bioretention devices are provided for each of the 2 site catchments and are located
                       in areas of landscaping
                      Parking and driveway areas are delivered to the bioretention devices as surface
                       flows (i.e. not in pipe) through grading of the parking surface and use of up-stand
                       kerb. This has allowed the bioretention basins to be setdown a minimal distance
                       below the level of the parking modules so the marcophyte plantings will be clearly
                       visible from both the street and the car park and thereby enhance the amenity of the
                       development
                      Roof areas are delivered to bioretention devices though a piped roofwater system
                       which may discharge to the devices via a surcharge pit (subject to detailed design)
                      Minor areas of the site (driveway ramp and external landscape batters) are not able
                       to drain back to the bioretention devices (as they are lower than these devices).
                       These areas have been accounted for in the modelling and it is proposed that some
                       sediment and gross pollutant removal is provided for these areas by including a litter
                       basket within the existing side entry pit in Hilton Terrace.




SWMP – 11-19 Hilton Tce Tewantin                                                                                4