Appendix B - Stormwater Management Plan

      Unfortunately there is no room between houses 31, 29, 27 and 25 Tait Street and their side boundaries to
      allow a 3m wide overland flow path and underground drainage. There is however enough for a 1.5m wide
      inter-lot drainage outlet which our Client has negotiated permission from the Owner to construct. This will
      allow properties in our Clients development on the low side of the new road to drain to Tait Street.

5.2       Proposed Drainage System

The proposed road through new estate at 20 Eagle Drive Tewantin (Lot 6 RP149498) has a catchment generally
in accordance with Council’s original master drainage plan (Council Master Catchments no 2153 & 2154 in the
Appendix). There is some un-avoidable diversion of flow as a result of road construction, hence the importance
of providing an overland flow path through the low point (sag) at 14 Eagle Drive. The overall catchment flow to
sag point in Tait Street road reserve (opposite 25-27 Tait Street) is however unchanged.

The benefits of the local community are significant for installing a bio-retention/detention basin at 14 Eagle Drive
and are listed below:
     Provide a Q100 overland flow path which the existing catchment outside the development needs.
     Provide 845m2 of additional park/drainage reserve which will extend from the existing park to Eagle
          Drive
     Removal of the regular flooding issues associated with No. 14 Eagle Drive that Council would eventually
          have to address.

5.2.1     Bioretention/Detention Basin Capacity

The Bioretention/Detention basin size at 14 Eagle Drive is only designed for reducing main catchment at 20
Eagle Drive Tewantin (Lot 6 RP149498), and proposed lot 7 on 35A Tait Street Tewantin (Lot 10 SP241386) with
an area of 1.585Ha (refer plan 1702-01B). The previous smaller detention basin on plan 1403-15A was designed
for a catchment of 1.04Ha (lots 1-5 and 7-9 not included). The detention basin has been made narrower and
longer to provide more space around it and treat the larger area with a 420cum volume, refer to plan 1702-02A
and sections on plan 1702-03A.

5.2.2     Drainage Improvements/Non Worsening

Point 5.1.1 – 5.1.3: Properties at 14 and 16 Eagle Drive.

The property at 14 Eagle Drive is to be demolished to provide an overland flow path from surrounding area.

This will reduce issues at 16 Eagle Drive because as noted the lack of flow path through sag point backs water
up in the road which eventually flows into 16 Eagle Drive.

It is also planned to install a footpath in front of 16 and 18 Eagle Drive to obtain a minimum 100mm verge height
above top of kerb. Works will also involve driveway revisions to maintain the 100mm verge height at 16 and 18
Eagle Drive. The verge at 12 Eagle Drive will have minor fill of approximately 100mm and turf to maintain 100mm
height of verge above top of kerb level. Refer to plan 1702-02A. These works will also enable the northern Q100
road flows from new subdivision and existing area of 1.92Ha (1.128cumecs) to get to sag at 14 Eagle drive with
flow a maximum of 50mm above top of kerb to QUDM flow limitations.

The proposed overland flow path and depths are shown on plan 1702-03A. The overland flow in Q100 is below
maximum dV of 0.6m/s², and while a lower dV would be preferred the path exits to open grassed parkland with
shallow slow moving sheet flow and no adjacent inlet system. The outlet location is therefore low risk to
requirements of QUDM.




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