Planning Report - 14-16 Mary Street, Noosaville - Bounce Hostels 15.6.2018

   Basement Ramp Stormwater
        The access ramp to the basement carpark will be exposed to the weather and therefore run off from
        the ramp will need to be collected and disposed of. It is proposed to install a grated drain at the base of
        the ramp to collect runoff. This will be discharged into a sealed storage tank and pump below the
        basement car park which would be set up to pump to the street during a rainfall event.
        It is necessary to have a sealed collection tank instead of a soak away pit due to the groundwater levels
        for the site being above the basement level. A soak away drain located at the basement level connected
        to the grated drain would, at times, act in reverse and allow ground water into the basement (refer to
        Geotechnical Investigation prepared by Core Consultants enclosed within Appendix H).
        The catchment area of the ramp is approximately 84m2, so a 2500 litre tank would also provide
        emergency storage for the equivalent of a 30mm rainfall in the event of a power failure.
        In an extreme event, coinciding with a power failure, the basement area would offer additional storage
        capacity. For example, if 500mm of rain was to fall with power being off, the depth of water
        accumulating in the basement would be only 53mm in depth. To put this in perspective, data from the
        Bureau of Meteorology indicates that the maximum daily rainfall recorded at Tewantin was 310mm in
        August 2007 – refer attached. The grated drain, storage tank and pump system would also be able to
        dewater the basement area once the power was restored. It should be noted that the storage tank and
        pump is not required to keep flood waters out of the basement.




Existing Sewer Infrastructure

A trunk sewer line crosses the site approximately 13 metres from the rear boundary. The sewer is currently
2.5-2.8 metres below the existing surface level. As a result of the raised ground levels required, the sewer will
ultimately be over 3.0 metres deep.
Discussions with Unitywater have confirmed that for a 3-metre-deep sewer line, Unitywater will require the
proposed buildings to be set back a minimum of 3 metres from the centreline of the sewer and founded below
the zone of influence. This set-back is depicted in drawing DA.01 in Appendix A.
The balconies that cross the sewer line and connect the rear accommodation pavilion to other buildings have
been designed to be removable in the case that access is required. The balconies will be engineered as if to be
temporary structures, so they are able to lift-on and off if required.




              14-16 Mary Street, Noosaville                                                       25