Engineering IR Response

In reply please refer to:
Our: Troy Paulsen
At: Sunshine Coast
Our Ref: SC-8839

     18th May 2021

     Noosa Shire Council
     PO Box 141
     Tewantin QLD 4565


     RE:       SITE         BASED   STORM   WATER    MANAGEMENT          PLAN     FOR    PROPOSED
     APPARTMENTS AT 31 BOTTLEBRUSH AVE, NOOSAVILLE


     1. INTRODUCTION
     The proposed development consists of a multi-apartment development and associated car
     parking. The site is fronting Bottlebrush Ave to the South West and existing residential
     allotments to the remaining boundaries. The site is currently occupied by a single two story
     residential dwelling with its associated access driveway. The total site area is 506m 2 and has an
     approximate fraction impervious of 46% (Fi = 0.46).


     2. STORMWATER CONNECTION
     Under existing conditions, stormwater runoff discharges to the kerb and channel fronting the
     subject site, before falling to the North West before flowing into the existing 300mm diameter
     underground stormwater network. The proposed stormwater will continue to discharge into the
     Bottlebrush Ave kerb and channel in accordance with local council’s discharge flow rates of
     maximum 25L/s.


      3. STORMWATER QUANTITY
     The proposed development will increase the impervious nature of the site compared to pre-
     development to a fraction impervious of 80% (Fi = 0.80). Therefore, peak flow mitigation is
     proposed to limit minor and major flows (50%, 20%, 10%, 5%, 2% & 1% AEP), to that of the
     pre-development scenario to ensure the downstream pipe capacity is not worsened.