B07056.W-01A Complete - Stormwater [As Published] · 132007.2398

Concept Stormwater Management Plan
RSL Care – Cooroy Retirement Village

7.2.2              Roof Details

All buildings within the site contribute to a total roof area of 2.91ha. For the water balance analysis it was
assumed that:
      •   100% of total roof area contributing to capture. A separate piped drainage system is proposed to drain
          roof runoff from ILU’s and Apartment buildings for collection in underground tanks. The RAC building
          also has an underground tank at its eastern end (low side) so it is also assumed that 100% of the roof
          area can drain to the tank.
      •   Coefficient of Runoff value of 0.9 was used as per HB 230 – 2006: Rainwater Tank Design and
          Installation Handbook.

7.2.3              Usage

Variables assumed for water usage have been adopted from Maroochy Shire Council’s Integrated Water
Management Guidelines (2006). While current estimates of water consumption indicates a usage of
300L/person/day, the target of 240L/person/day represents MSC’s Planning Scheme Policy. On the basis that
efficient water use is proposed within this development, the reduced usage rate has been adopted. For the
Residential Aged Care building, usage was assumed to be lower at 180L/person/day.

Occupancy of 1.5 persons/dwelling has been adopted for the ILU’s and Apartment buildings according to The
Noosa Plan for Retirement or Special Needs Housing giving a total daily use of 360 L. For the Residential Aged
Care building, an occupancy of 120 persons was adopted based on the number of beds proposed. As per the
Maroochy guidelines, the proportions and breakdown of rainwater use per dwelling is indicated in Table 7.2.

                                       Table 7.2: Breakdown of Total Water Usage
                   Use                      Proportion of Total Use    Rainwater Tank Use (L/day)
                   External                          30%                          108
                   Toilets                           20%                           72
                   Laundry                           15%                           54
                   Hot water                         20%                      Not applied
                   Kitchen / Bathroom                15%                      Not applied
                   Total                       100% ( = 360 L)                    234


An irrigation rate of 25mm/m2/week has been assumed landscaping areas around the apartment, residential
Aged Care and Village Centre Community Buildings. A total of area of 1.56ha is proposed for irrigation.

7.3                Water Balance Results
7.3.1              Existing & Developed Scenarios

To calculate the runoff generated by the site for the existing and developed scenarios, Average Volumetric
Runoff Coefficients (AVRC’s) were used in combination with the site 30 year daily rainfall data. AVRC’s of 0.30
and 0.49 were used for the existing and developed scenarios respectively. The resultant Average Annual Runoff
Volumes (AARV’s) for the two scenarios are presented below in Table 7.3.




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