2008/0169 Response to information request - 71 Seaview Tce Sunshine Beach · 132008.169

4.7       DETENTION OF POST DEVELOPMENT FLOWS

To ensure post development stormwater flows are limited to those occurring under current conditions, runoff
from the developed portion of the site will be attenuated via an underground storage system.


The storage required to achieve a non-worsening of flows from the site is 60kL (60m) . To achieve this storage
capacity the following options are available:


      •    Single underground Storage Tank of 60kL with staged outlets
      •    Multiple underground Storage Tanks throughout the site with a total storage capacity of 60kL
      •    Single underground infiltration system (Atlantis Cells/Slotted FRC Pipe/ or approved equivalent) with 60kL
           of storage capacity
      •    Multiple underground infiltration systems (Atlantis Cells/Slotted FRC Pipe/ or approved equivalent) with a
           total storage capacity of 60kL


The outlet from the storage system will be on the downstream side of the proposed retaining wall. Each outlet
will be constructed with an energy dissipater to ensure there will no scouring effects on lands downstream of the
proposed development. The scour protection for the outlet/s from the storage device/s will be similar to that
shown in Figure 7 for the outlet on the western boundary of the site.


A preliminary location of the proposed storage devices and outlets is shown in Figure 9. Actual location of
storage device/s and outlet/s will be determined at the operational works stage of the application.




 SITE BASED STORMWATER MANAGEMENT PLAN - Revision D    71 Seaview Tei race. Sun;hin< Beach                         11