Attachment 8 - Interim Stormwater Management Plan - TOPO · 132005.638.06

R5304: NOOSA RESOURCE RECOVERY CENTRE - STORMWATER MANAGEMENT PLAN



       +      Any sediment basin designed in accordance with this list must be operated in such a manner that within 120
              hours of the most recent rainfall event, the required design capacity of the upper settling volume is available for
              capture and storage of stormwater runoff from the next rainfall event.
       +      In addition to the settling volume requirements, sediment basins should be designed with a sediment storage
              zone equal to 50 % of the upper settling volume, or the volume of the sediment determined by estimating the
              expected sediment runoff volumes over the desired maintenance period of not less than 4 months.

1.6.1.1.         CLEAN WATER DIVERSION
A key component of managing surface waters is the diversion of ‘clean’ runoff away from disturbed portions of the site.
Clean water is defined as water that either enters the property from an external catchment and has not been further
contaminated by sediment within the site, or water that has originated from the site and is of such quality that it does
not need to be treated in order to achieve the required water quality standard, or would not be further improved if it
was to pass through a sediment trap (IECA, 2025).

In diverting clean water around the disturbed portions of the site, it will remain separated from the sediment laden runoff
that requires treatment. It is important that clean water diversion drains are constructed prior to new areas being
disturbed to reduce the likelihood of runoff being contaminated. This management technique has the potential to
greatly reduce the size and operational costs of treatment devices. The clean water drains should be designed to convey
runoff associated with the 10 % Annual Exceedance Probability (AEP) event, in accordance with the Guideline Stormwater
and environmentally relevant activities (DES, 2021).

1.6.1.2.         DIRTY WATER DRAINAGE
Dirty Water Drains (DWD) and diversion bunds are required to convey sediment laden runoff from disturbed areas to
the sediment basin. The dirty water drains will also be designed to convey runoff associated with the 10 year ARI critical
duration event, in accordance with the Guideline Stormwater and environmentally relevant activities (DES, 2021).

1.6.2.           SEDIMENT CONTROL.
To achieve the required release criteria, treatment of dirty site runoff will be required in a Type 1 treatment system. In
accordance with the site permit, sediment control measures must be implemented and must have the hydraulic
effectiveness to treat stormwater for 90 % of the annual runoff for each stormwater catchment. A HES basin is proposed
to achieve this objective, with further details provided in later sections of this report.

1.6.3.           EROSION CONTROL
Erosion control measures aim to prevent or reduce soil erosion caused by raindrop impact and sheet flow. One of the
most effective forms of long term erosion control is the stabilisation of disturbed areas. Where possible, progressive
stabilisation and revegetation of the non–operational areas must be undertaken. If an area is to be non–operational for
only a short duration, temporary measures (such as mulch/compost blankets or jute matting) must be applied.
Temporary stabilisation should also be provided as works are progressing towards the final level, and this can be achieved
through the application of soil binders. Stabilisation of high traffic areas should also be provided, particularly at the truck
unloading points. Stabilisation can be achieved using a layer of crushed concrete, ideally 150 – 200 mm thick or gravel.




Environment. Engineering. Education.                                                                                      PAGE 5