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Resilient urban systems:
a socio-technical study of community scale climate change adaptation initiatives
Functional diversity:
Examples at both sites include the ability to heat water using gas or solar energy and
the capacity to switch from community scale wastewater treatment to mains treatment. Plans to gravity feed
recycled water to residents from a hill-top reservoir at Aurora will also diversify the way water is supplied to
residents, ensuring that supplies will be unaffected by temporary blackouts or pump failures. At WestWyck,
the capacity to switch from on-site grey and rainwater collection and water pumping to pressurised mains
water to fill tanks and hot water systems demonstrates three areas where functions (water collection,
distribution and storage) can be provided in multiple ways if a problem occurs. As described by one
stakeholder:
“[When something goes wrong] the first thing we usually do is go into a controlled
management phase and say ‘ok, we’ve got a problem so let’s divert the system so that
it’s not gonna cause grief…’ So we bypass it – go back to conventional technology… just
go to the bypass, just turn the tap, so now they’ve got water from the mains rather than
water from the [on-site] system.” (S3)
Resource diversity:
The provision of both potable and non-potable water to both developments is
significant from a resource diversity perspective. At the time of this assessment, the quantity of recycled
water exceeded demand at Aurora but this is expected to change as additional settlements are connected
to the recycled water grid. At WestWyck, demand for alternative water sources exceeds supplies but
the diversity of sources (rainwater, mains supply and recycled grey water) is greater than at Aurora. The
advantage of this configuration is reduced reliance on any single source.
By diversifying water supplies, the systems at both developments reduce demand on mains reticulated
supply. Although the volume of mains water saved is a very small proportion of overall mains supply, both
system models indirectly augment mains storage capacity (a form of redundancy). Improved system
resilience at Aurora also stems from the capacity to store partly treated (Class B) water and fully treated
(Class A) recycled water as a back-up when demand exceeds supply.
Fail-safe mechanisms:
Various fail-safe mechanisms are used as part of the water systems at both
developments. Examples include passive overflow functions built into sewerage systems at both sites,
which prevent uncontrolled discharge in the event of excess supply (e.g. caused by stormwater infiltration).
As a member of the WestWyck Owners Corporation describes:
“Ultimately what we’re relying on is diversion systems, so that if our local Green systems
were to fail then we can plug in to the major infrastructure that’s there, like if our black
water system fails we can divert to sewer, if our grey water system fails we divert to mains
water.” (S3)
Design for modification:
The Aurora wastewater system has been designed to allow expansion of
treatment capacity as demand increases. This type of modification does not affect the core structure or
functions of the system (S7).
Feedback mechanism:
Water systems at both developments include a range of fault detection and
alert technologies that provide system managers and also users (in the case of WestWyck) with real-time
information on the performance of water treatment processes. At WestWyck manual switching between
water supplies is currently required in response to a malfunction in water treatment but will soon be
converted to a remote (telemetry-controlled) switch. Additional mechanisms such as emails and a paging
system are also used to assist in the feedback of information between WestWyck residents and WOC.
(Anon, 2011)