2160 IWMP Report_Jan2022

                                                                                 Callaghan & Toth

TABLE 4.1           MUSIC CATCHMENT AREAS (DEVELOPED)

              Catchment                    Land Use            Music Impervious       Area (ha)

          Habitable Roof Area              Commercial               100%                0.3892
             (Catchment A)

       Car Park to Bio-retention           Commercial                90%                0.0387
           (Catchment B1)

       Car Park to Bio-retention           Commercial                90%                0.0571
           (Catchment B2)

              TOTAL                                                                    0.4850ha


4.2.2 Treatment Nodes

The “MUSIC Modelling Guidelines for South East Queensland” Version 1 prepared by Water by
Design and dated December 2010 has been used to set the rainfall runoff parameters and
pollutant export parameters for the site.

The land use type used for this model was “Commercial” and the values in the guideline shown
in Table 3.7 and Table 3.8 of the guidelines have been used in this model.

Rainwater Tanks have been provided for the roof catchment as shown on the plans. The Reuse
allowed is for:

     1. A daily re-use onsite will be as follows: toilet reuse + laundry reuse = total reuse
     2. Toilet Reuse: 21L/person/day per toilet = 21 litre x 1 person x 45 toilets = 945 L/day

     3. Laundry Reuse = (pervious ground area) x (portion of area irrigation) x (annual irrigation
           rate) = volume / year
           = 1,030m2 x 75% x 0.548m = 546 kl/yr
           Daily rate = 1467 L / day

               Total Daily Reuse = 945 + 1,467 = 2,412 L/day

Three (3) tanks are proposed (2 existing and 1 new) a total of 72,000 litres on site, which will
supply reuse water. The overflow from the rainwater tanks flows to the bio-retention basin that
drains to the southern vegetated area within the site.

Bio retention Swale is adjacent the carpark in catchment B2 and will treat runoff from this
catchment and rainwater tank overflows. The bioretention swale is 1m wide at the base, 2.6m
wide overall and 28m long. It has a 1% grade flowing into the Bioretention Basin. The size of
this system has been designed in accordance with Plan 2160-03.

Bioretention Basin has been placed close to the edge of car parks to treat runoff from
Catchments B1, B2 and rainwater tank overflows. One (1) bio-retention basin has been used,
with an area of 36m2. It has a filter layer depth of 0.3m and an extended detention depth of
0.6m. The size and depth of the system has been designed in accordance with Water By
Design guidelines and this system is in place. The bio-retention basin drains to vegetated area
within the site.

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2160, Kabara Upgrade, Cooroy             IWMP.doc                              January 2022