06-09-22 Stormwater Management Plan_Issue F · MCU21/0175

 6 September 2022




5.4.3.5 Water Quality Objectives
The Water Quality Objectives of the receiving waters for the proposed development have been
obtained from State Planning Policy July 2017. The State Planning Policy load reduction targets are
summarised in Table 3 below.


                                              WATER QUALITY OBJECTIVES


 Total Suspended              Total Nitrogen                  Total                     Litter/Gross
  Solids (TSS) %                 (TN) %                   Phosphorous                   Pollutants %    Oils/Grease
    Reduction                   Reduction               (TP) % Reduction                 Reduction

                                                                                                       No visible films
           80                          45                             60                       90
                                                                                                         or odours
                                             Table 3 – Water Quality Objectives

5.4.3.6 Treatment Plan
In order to achieve the Water Quality Objectives for the proposed development, it is proposed to
use natural treatment methods to treat the runoff prior to discharge from the site.

Stormwater runoff from the roof will be captured in a series of new gutters, downpipes and pits,
which will discharge along with the remaining on ground catchments to bioretention basins, where
Q1 flows will receive treatment while additional flows with discharge into the external stormwater
network.

Runoff from the existing landscape areas at the North and South East corner of the site will remain
generally as per pre-development conditions and will be treated by the existing grassed swale.

Runoff from the west and central parts of the development will sheet flow toward a narrow
bioretention basin fitted in the middle of the carpark, adjacent to the arbour link. Surrounding
runoff will fall toward the southern bioretention basin via kerb and crossfall. Similarly, the eastern
section of the development will sheet flow toward two bioretention basins on the south-east
corner of the site. Once sheet flow is conveyed within the basins, stormwater will be piped toward
the lawful point of discharge.

Approximately 310m2 of the access driveway and the carpark will bypass the bioretention basins.
This has been allowed for in the model so the overall net water quality objectives are achieved for
the development

Treated water will discharge off site via a proposed stormwater connection. The treatment plan for
the proposed development is depicted on MPN Plan 8293-CP.1.01 attached in Appendix 3, with
MUSIC excerpt below.




 Excellence with Economy in Engineering                                                                                   11
 https://mpncnetau.sharepoint.com/sites/administration/shared              documents/8000-8999/8200-
 8299/8293/reports/06-09-22 stormwater management plan_issue e.docx