Appendix B - Stormwater Management Plan

SUMMARY
The key points of this investigation are as follows:

     1.    Provide a Stormwater Management Report to Noosa Council Requirements.
     2.    Identify external catchment stormwater influence on mitigation measures.
     3.    Stormwater flows into and through the site including 29 Tait Street.
     4.    Capacity of downstream drainage system in Tait Street to cater for additional runoff.
     5.    Identify Detention basin and bio-retention dimensions.


1.0        INTRODUCTION
This integrated water management plan (IWMP) has been prepared for the new subdivision project at 20 Eagle Drive
Tewantin.

This Integrated Water Cycle Management Plan (IWMP) includes detail on the management of rainwater, and
stormwater flows.

2.0        RESPONSE TO RECONFIGURATION INFORMATION REQUEST
The enclosed report shows calculations to support proposed stormwater management solutions for quantity and
quality.

There will be some treatment of external stormwater as a result of proposed strategy. The external catchment
stormwater will be treated as follows;

          Stormwater Quality: Stormwater drainage pipes from subdivision will capture majority of minor flows (1.056
           Ha of 1.585 Ha) for treatment in bio-retention basin in no 14 Eagle drive. To avoid the need to directly treat
           lots that fall away from the road (proposed lots 1-5, 7-9) 0.529 Ha of external catchment will also be treated.

           To proportion external intake of remaining 0.529 Ha at Operational works detailed stormwater calculations
           of pit and pipe systems in the subdivision will be completed, water from upstream catchment and area
           around 14 Eagle drive and size an inlet/pipe system to suit. There may be additional pits outside no 14
           Eagle Drive to take additional flow as shown on plan 1702-02A.

          Stormwater Detention major road flows from external catchment will be directed to no. 14 Eagle Drive.
           Calculations have been completed to proportion flow as follows for Q100 (rational method):

                    1.   Subdivision Q100 overland water into detention basin to attenuate flow          0.175 m3/s
                    2.   Q5 subdivision piped flow into detention basin to attenuate flow                0.481 m3/s
                    3.   Upstream flow (already detained) less 0.05 m3/s roofwater                       0.124 m3/s
                    4.   Water from new sag pits at 14 Eagle Drive into detention basin attenuate flow   0.164 m3/s
                    5.   Overland flow down pathway at 14 Eagle Drive                                    1.101 m3/s
                    6.   Existing pipe flow from sag outside 14 Eagle Drive                              0.540 m3/s
                    7.   Overall flow of 4.514Ha external catchment to 14 Eagle Drive                    2.585 m3/s

           Note the sum of items 1-4 is 0.944 m3/s, which is the Q100 flow from 1.585 Ha of new subdivision to be
           attenuated in detention basin.

           Future upstream roof-water from behind lot 20 will be connected to the roof-water system through 29 Tait
           Street as noted in item 3. This pipe system in Tait Street was designed some time ago for this catchment.




Eagle Rise Estate                                                                                                pg. 3