2021-01-27 Special Meeting Agenda

SPECIAL MEETING AGENDA                                                           27 JANUARY 2021


Furthermore it is acknowledged human behaviour will also reduce the risk as people will be less
likely to use the park when it is raining and likely to leave the site once rain commences. Whilst it
would be preferable for there to be additional time to allow for the evacuation of the site the 26
minutes between when the site starts to be inundated and when the southern-most pathway
(evacuation route) begins to inundate is considered to provide an adequate timeframe for a person
to leave the site.
It is also noted that the applicant’s estimate of the lateral spread (velocity) of the water at
approximately 0.05m/s is significantly slower than the estimated average walking velocity for a 3 -
6-year-old which is 0.84m/s.
Additionally it is not uncommon for facilities such as parks and playgrounds to be located in areas
subject to flood risk noting that the skate-park and tennis courts on the opposite side of Maple
Street are also subject to flooding.
Water quality
Both applications were referred to a consulting hydraulic engineer for review.
With regards to the car park it is proposed that the new areas of car parking would drain to an
existing bioretention device which would be refurbished as part of this application.
The existing bioretention device is 144m2 and the complete catchment draining to this device is
1.921ha. This corresponds to a size of 0.7% of the contributing catchment. This is slightly below
the expected size for this landuse, however there are also significant sections of swales included
in the treatment train which will be effective at reducing Total Suspended Solids (TSS) which is
often the limiting pollutant.
The consulting hydraulic engineer notes that a MUSIC model has been provided with the
application which contains issues so cannot be relied upon. The issues include:
     The model and results include other discharge points and catchments in vicinity of the
      development but which are not part of it. This has the effect of masking the results from the
      application areas
     The model includes ‘existing’ devices which in the admission of the Storm Water
      Management Plan (SWMP) authors may not actually exist
     The modelling of the existing Gross Pollutant Traps as receiving roofwater overflow may not
      reflect reality
Council’s consulting hydraulic engineers recommends that an updated Stormwater Quality
Management Plan and engineering drawings based on a revised model be provided noting that
there is ample opportunity to incorporate additional stormwater treatment measures if required.
Accordingly conditions are recommended, for the car park application, incorporating the advice of
the consulting hydraulic engineer.
The playground application has been supported by a SWMP and various small-scale treepits and
bioretention devices are proposed. To trigger the pollutant load reduction SPP targets, the
playground would need to be >2500m2 in area and result in >25% imperviousness. While the area
threshold is exceeded, the figures presented in the SWMP show the playground as only 24%
impervious, so the playground does not need to demonstrate compliance with the load reduction
targets. The measures provided can therefore be considered as a best-practice addition rather
than a statutory requirement.
Riparian Buffer
Both the car park and the playground are located almost fully within the Riparian Buffer. The
superseded planning scheme seeks to avoid any new development within the Riparian Buffer area
for the purpose of protecting the biodiversity and ecosystems values. However, it is noted that in
this area there are many instances of intrusion into the riparian buffer by a range of historical
developments including:


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