Appendix F Engineering Report - 14-16 Mary Street, Noosaville - Bounce Hostels 15.6.2018

     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 Geotech
     report). 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.

3.       Acid Sulphate Investigation and Management

     Please refer to the separate report prepared by Core Consultants.

4.       Stormwater Management

         4.1. Existing network and legal point of discharge

     Stormwater from the site would need to be piped to the street and discharged to the kerb and channel
     using kerb adaptors as there is no existing stormwater pits in front of the development site to connect
     to. The nearest stormwater pit is located approximately 40m to the east. An inspection of this pit has
     identified that the invert level is less than 1.0m below the road surface. Based on minimum allowable
     pipe grades and sizes, and existing road levels there would insufficient cover if a pipe was extended
     from this pit to the closest point in front of the development site. Note the existing kerb and channel
     has a grade of less than 0.5% and falls both east and west from the area in front of the site. ie the site
     is located at the crest of the road. The discharge from the site would therefore be split to the east and
     west side of the building and discharged to the street at both sides of the property. The reception area
     roof area could be separately piped directly to the kerb and channel. The number of discharge points
     can be determined during the detailed design of the building hydraulic plans.

         4.2. Stormwater Quantity

     The existing building and concrete pavement areas on the site have a combined area of 875m2. In
     addition to this there is over 1080m2 of unsealed compacted gravel hardstand parking area surrounding
     the existing building – this is best viewed in the 2015 aerial photo. Refer marked up aerial plan below
     showing these areas. Given the nature of this hardstand pavement we believe that, conservatively,
     50% of this area can be included in the impervious area of the existing site. As such the total impervious
     area for the existing site is effectively 1415m2. The proposed development includes buildings and
     impervious (paved areas) totalling 1433m2. Note the drying area on east side of building will be either
     permeable paving or turfed. As there is only a minor increase in the impervious area we contend that
     on-site detention is not necessary.




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     17699 - Bounce Hostel, 16 Mary Street Noosaville – Engineering Report – Rev A