20220206 48 Elm St SWMP

 CONCLUSION
This Stormwater Management Report has outlined how the stormwater run-off from the site is to be managed to
comply with the relevant requirements and minimise any adverse impacts to the downstream catchments.

         The lawful point of discharge for the development will be by connection into the existing stormwater
          infrastructure in Pearl Street to which the site currently drains.

         The overall run-off characteristics from the site will be maintained with no worsening to existing peak flow
          rates. DRAINS modelling has been carried out for existing and developed conditions to determine the
          required sizing of an OSD tank to attenuate peak site flows to the existing rates. A 13kL OSD tank will be
          used to collect run-off from the roof areas to achieve the required attenuation.

         A Humes Stormtrap has been nominated for the OSD tank. A 115mm diameter orifice plate is required at
          the outlet to attenuate flows to existing levels. A grated maintenance access will be provided in the top of
          the tank. This will also serve as an OSD tank overflow during the 1% AEP and 2% AEP events.

         A new inlet pit will be constructed in the north eastern corner of the site over the existing 300mm roofwater
          pipe. The proposed carpark area will grade towards this inlet pit via a kerb provided along the eastern edge
          of the carpark.

         A 225mm outlet pipe will be provided from the OSD tank to the proposed inlet pit.

         The existing roofwater pipe has adequate capacity to allow for construction of a new inlet pit and connection
          of the site stormwater.

         No water quality improvement devices are proposed for the site as the site area is less than 2,500m2 and
          are therefore not required under the State Planning Policy (2017).

         During construction, erosion and sediment control measures are to be implemented to minimise potential
          contaminants impacting the downstream receiving environment in line with the objectives of Appendix 2 of
          the SPP. A site-specific erosion and sediment control plan has been developed using best practice
          management principles to achieve these objectives.

         The proposed stormwater solution is considered to minimise any adverse impacts to the downstream
          environment arising from the stormwater run-off while also meeting the stormwater quality and quantity
          targets required for the development and is therefore a complying solution for the proposed development.




Project number 20220206                                                                              Page 16 of 19
File 20220206 48 Elm St SWMP, 2023-02-03 Revision 1

P +61 7 5211 1003             A 75 Noosa Drive, Noosa Heads Qld 4567   E [email protected]      recorconsulting.com