24-7-19 Attachment F Rev Stormwater Mgmt Plan

18 July 2019


5.3.3.9.1      Heavy Metals
Heavy metals in stormwater runoff generally become attached to fine sediment. The bioretention
basin will remove the majority of this fine sediment. The removal of the fine sediment should
effectively remove most of the heavy metals in the runoff.

5.3.3.9.2       Pathogens/Faecal Coliforms
Domestic animals within the development will be under the control of their owners at all times and
the owners will be expected to clean up after them.

5.4       Proposed Stormwater Quality Treatment Devices

5.4.1 Locations

The location of the proposed stormwater quality treatment device is shown on MPN Plan 7700-
DA.01 attached in Appendix 3.

5.4.2 Device and Size

The device type and size are depicted on MPN Plan 7700-DA.01 attached in Appendix 3.

5.4.3 Operation

The bioretention basin operates by filtering runoff through densely planted surface vegetation,
then percolating the water through a sandy loam filter media with details as per MPN Plan 7700-
DA.01 attached in Appendix 3. As the water is percolated through the soil, pollutants are captured
by fine filtration, adsorption and biological uptake.

5.4.4 Maintenance

For the initial maintenance of the bioretention basin it is important to remove weeds and debris,
with regular watering until plants are established and actively growing.

Watering is to be undertaken following the construction of the basin at the following frequency:

          Week 1 – 6, 5 times/week
          Week 6 – 10, 3 times/week
          Week 11 – 15, 2 times/week

If there is no rain, each plant should receive 2.5 – 5.0 litres of water per week during establishment
in the first 6 weeks (40mm/week).

Watering requirements to sustain healthy vegetation should be determined during ongoing
maintenance visits.

Detailed establishment techniques can be found in the Water By Design Construction and
Establishment Guidelines.

Inspections are also recommended following large storm events to check for scour and other
damage.




Excellence with Economy in Engineering                                                                   15
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